Startseite Effects of acid hydrolysis waste liquid recycle on preparation of microcrystalline cellulose
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Effects of acid hydrolysis waste liquid recycle on preparation of microcrystalline cellulose

  • Huijuan Xiu , Rui Cheng , Jinbao Li EMAIL logo , Feiyan Ma , Te Song , Xue Yang , Pan Feng , Xuefei Zhang , Evguenii Kozliak und Yun Ji EMAIL logo
Veröffentlicht/Copyright: 18. Mai 2019
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Green Processing and Synthesis
Aus der Zeitschrift Green Processing and Synthesis Band 8 Heft 1

Abstract

Large amounts of acidic waste are produced on the industrial scale during hydrolysis of partially amorphous cellulose to produce microcrystalline cellulose (MCC). The essential disposal and treatment of this highly acidic liquid wastes the acid feedstock and increases the production cost. To maximize the use of acid without sacrificing the MCC product quality, this project reports a successful attempt to recycle the acid hydrolysis waste liquid, focusing on the impact of waste recycling on MCC morphology and reducing sugar in the hydrolysate. The results showed that when the waste liquid is recycled 1-5 times, no metal accumulation occurred while cellulose particles remained intact, maintaining their shape and size. Their extent of crystallinity remained nearly constant, even increasing slightly with up to three cycles. The concentration of reducing sugar showed growth when recycling the waste liquid up to three times, although not quite to the levels that would allow for its cost-effective fermentation. The acid amount to be added at the start of each cycle was near 50% of that used on the first stage.

Keywords: acid hydrolysis; waste liquid; recycling; microcrystalline cellulose

1 Introduction

Microcrystalline cellulose (MCC) is an important plant based powder material, which is produced from biomass by dilute acid hydrolysis. It has been widely used in medicine, food, cosmetic, leather and many other industries as functional additives because of its high crystallinity, high flowability and low water solubility [1, 2, 3, 4,]. MCC is a purified partially de-polymerized crystalline polymer. Acidic treatment of purified cellulose under well-specified conditions hydrolyzes only the amorphous areas of this polysaccharide while the crystalline domains remain intact [5]. However, a large amount of acidic waste is produced during the MCC production process by acid hydrolysis method. The acid hydrolysis step produces large amounts of waste liquid, which contains mainly the added acid, along with reducing sugars and other cellulose degradation components. A direct discharge of this waste liquid to the environment would result in water and soil pollution, primarily due to high acidity. Thus, industrial production lines typically use NaOH or Ca(OH)2 to neutralize the waste stream, then transferring it to a wastewater treatment facility. This treatment wastes significant amounts of acid and, at the same time, discards potentially useful organic compounds, as the Chemical Oxygen Demand (COD) content of such wastewater remains high after the acid neutralization [6, 7,].

If the waste liquid could be recycled, not only the environmental impact but also acid usage and neutralization costs would be reduced, with potential utilization of the accumulated sugar. Sarma et al. applied a combination of membrane technology and activated carbon (AC) adsorption to remove both reducing sugars and carbohydrate oligomers from waste liquid followed by a re-use of the resulting sulfuric acid containing liquid [8]. Strathmann proposed a partial acid recovery with a cation selective membrane after hydrolysis of lignocellulose with sulfuric acid, while the other part was converted to SOx gas and subsequently to sulfuric acid. However, membrane based technologies, though featuring effective acid separation, require significant investments and logistical support [9, 10,].

It is of note that the acid hydrolysis waste liquid obtained as a result of MCC preparation has a relatively high acid and low organic solid content. Thus, we postulated that direct recycling of the waste liquid can be applied to re-use the acid, without a damaging effect of by-products, as long as the number of cycles is limited. However, no direct recycling of waste liquid during MCC production has been reported to date, apparently due to the well-known side reactions caused by products of cellulose degradation.

Therefore in this project we have tested this hypothesis by recycling the waste liquid several times in a lab-scale reactor while adding only a fraction of fresh acid at the start of each cycle except for the starting stage. The effects of the number of acid hydrolysis waste liquid cycles were assessed on cellulose microfibril morphology, particle size distribution, crystallinity, yield and thermogravimetric curves. At the same time, changes in the reducing sugar concentration in waste liquor were monitored to explore whether this potential value-added product could be accumulated and used for ethanol production via fermentation.

2 Materials and methods

2.1 Raw materials and chemicals

Eucalyptus dissolved pulp was provided by Shandong Bapubeibo Pulp and Paper Co., Ltd (Shandong, China). Please not the raw materials for preparation of MCC are not limited to the dissolving pulp. Dissolving pulp was used in this study and its technical quality parameters are shown in Table 1.

Table 1

Eucalyptus dissolved pulp quality parameters.

α-cellulose content %Degree of polymerizationDegree of crystallinity %Whiteness % ISOAsh content %
92.6666158.9286.30.08

37% concentrated hydrochloric acid was purchased from FuChen Chemical Reagent Factory (Tianjin, China). The copper ethylenediamine solution was purchased from China National Pulp and Paper Research Institute (Beijing, China). All the chemicals were of analytical grade.

2.2 Preparation of acid hydrolyzed cellulose using recycled waste liquid

Dissolved pulp made of Eucalyptus was hydrolyzed using either fresh hydrochloric acid or hydrolysis waste liquid, which was circulated for 1 to 5 times. The acid hydrolysis experimental conditions were set up based on our previous research. 50 g of Eucalyptus dissolved pulp (oven dried weight) in 750 mL of a 2.5 M hydrochloric acid solution were placed into a KQ2200 ultrasonic cleaner (Kunshan City, China Ultrasound Instrument Co., Ltd.) with the ultrasonic power set at 80 W. Hydrolyzed cellulose was obtained by sonicating the reaction mixture at 80°C for 50 min, then the mixture was filtered and separated to obtain the liquid acid waste and solid hydrolyzed cellulose. Solid hydrolyzed cellulose was washed using deionized water to neutral pH and stored for further experiments. The entire amount of acid waste liquid was recycled for subsequent cellulose acid hydrolysis experiments, with the addition of some fresh acid to make up the acid loss during reaction. The yield of acid hydrolyzed cellulose was calculated by Eq. 1:

(1)Yield=DryweightofhydrolyzedcellulosegDryweightofcelluloserawmaterialg×100%

2.3 Analysis and characterization of acid hydrolyzed cellulose

A HITACHI S-4800-type cold field emission scanning electron microscopy - energy dispersive spectrometer (Japan Hitachi) was used to measure the morphology and residual metal content of the hydrolyzed cellulose. The average particle size and particle size distribution of the hydrolyzed cellulose were analyzed using a Mastersizer 2000 laser particle size analyzer (Malvern Instruments Ltd., UK). The thermal stability of hydrolyzed cellulose was measured by a Bruker STA449F3 TG-DSC synchronous thermal analyzer (NETZSCH, Germany). The scanning temperature range was 35 ~ 700°C and nitrogen was used as an inert gas. The heating rate was 10°C/min.

The crystallinity of hydrolyzed cellulose was measured using a D/max 2200PC X-ray diffractometer (XRD) (Rigaku, Japan). The samples were freeze-dried at –50°C for 24 h. The crystallinity test conditions were as follows: the maximum

tube voltage 60 kV, maximum tube current 80 mA, Cu Ka radiation (λ = 0.1518 nm), Ni filter, diffraction angle 2θ scan range 6-50°, scanning speed 2°/min. The sample crystallinity was calculated according to Eq. 2 [11, 12, 13,].

(2)Crystallinity=I002−IAmI002×100

where I002 is the diffraction intensity at a diffraction angle of 2θ = 22.5° and IAm is the diffraction intensity at a diffraction angle of 2θ = 18.0°.

2.4 Sugar, acid and metal content analysis in waste liquid

The reducing sugar content in the acid waste liquid was measured by the DNS method using a Model 722N visible spectrophotometer (Shanghai Jingke Instrument Co., Ltd., China) [14]. The metal ion concentrations was determined by the analysis of EDS spectra. The amount of acid was assessed by titration. The amount of fresh acid to be added at the start of each cycle was calculated as the difference between the initial and remaining acid amounts.

The error bars shown in Figures represent one standard deviation, indicating our experimental data have good repeatability.

3 Results and discussion

3.1 Microscopic morphology of hydrolyzed cellulose after several waste liquid cycles

Figure 1 shows the SEM images of hydrolyzed cellulose after several waste liquid cycles. As can be seen in Figures 1a-d, the hydrolyzed cellulose morphology was mainly represented by short rod-shaped particles, similar to the data reported earlier [15, 16,]. Only relatively small changes were detected between different samples. For cellulose obtained by a single passage hydrolysis

Figure 1 SEM image of hydrolyzed cellulose under different waste liquid cycles (a) uncycled (single passage), (b) recycled three times, (c) recycled five times, (d) an example of an agglomerated floccule.
Figure 1

SEM image of hydrolyzed cellulose under different waste liquid cycles (a) uncycled (single passage), (b) recycled three times, (c) recycled five times, (d) an example of an agglomerated floccule.

(uncycled), particles appeared slightly smaller (Figure 1a). After several cycles, the particle distribution became more uniform (Figure 1c). Perhaps, the most conspicuous change was observed concerning the agglomerated floccules, which appeared in all hydrolyzed cellulose products (Figure 1d). The number of such floccules consistently decreased with waste liquid recycling, becoming significantly less abundant after five cycles.

3.2 Effects of the number of waste liquid cycles on the average particle size and particle size distribution of hydrolyzed cellulose

The obtained particle size distribution profiles are shown in Figure 2. The average particle sizes of all hydrolyzed cellulose samples, both without recycling and with a varied number of cycles, were similar, with a maximum near 27 μm, thus corroborating the microscopic observations. The particle size distribution of hydrolyzed cellulose showed polydispersity, with most of the particles being within a range of 15 to ~ 50 μm. The difference in the size distribution between the recycled and non-recycled cellulose was not significant.

Figure 2 Distribution of cellulose particle size under different waste liquid cycles.
Figure 2

Distribution of cellulose particle size under different waste liquid cycles.

3.3 Effect of waste cycles on the crystallinity of hydrolyzed cellulose

Figure 3 shows the X-ray diffraction pattern of hydrolyzed cellulose that underwent a varied number of waste liquid cycles. The diffraction peaks at diffraction angles (2θ) of 15.3°, 18.2°, 22.8° and 34.7° correspond to the 101, 101, 002 and 040 planes of cellulose crystals, respectively, and so these crystals can be assigned to typical cellulose type I [17, 18, 19, 20, 21,], having better mechanical properties than other cellulose types [22]. The pulp raw material featured the same peak positions as those of the original cellulose, regardless of the number of waste liquid cycles, indicating that the crystal structure of cellulose was not altered after acid hydrolysis, with the number of waste liquid cycles having no effect.

Figure 3 XRD patterns of the raw material and hydrolyzed cellulose under a varied number of waste cycles.
Figure 3

XRD patterns of the raw material and hydrolyzed cellulose under a varied number of waste cycles.

Yet, the diffraction peaks at both the 101 and 002 crystal planes of the hydrolyzed cellulose obtained from the recycled waste liquid samples were stronger than those of both the raw material and the hydrolyzed cellulose treated only once, with fresh acid. The calculated degree of crystallinity of hydrolyzed cellulose based on the XRD patterns is shown in Figure 4, indicating an increase in cellulose crystallinity.

Figure 4 Changes in the extent of crystallinity of hydrolyzed cellulose under a varied number of waste liquid cycles.
Figure 4

Changes in the extent of crystallinity of hydrolyzed cellulose under a varied number of waste liquid cycles.

This qualitative observation was confirmed with quantitative measurements. The degree of crystallinity increased slightly yet steadily with the number of waste liquid cycles and reached the highest value of 82.2% when the waste liquid was recycled three times, while it was 79.4% when hydrolyzed cellulose was prepared with fresh acid.

However, when the number of cycles continued to increase further, the extent of crystallinity declined. After the fifth cycle, the crystallinity of hydrolyzed cellulose dropped sharply to 67.3%; this value failed to meet the requirement for MCC high crystallinity. Therefore to ensure the high quality of the final product, MCC, the waste liquid should be recycled only up to three times.

3.4 Effect of the number of waste liquid cycles on the reducing sugar content

To determine whether the reducing sugars produced by cellulose degradation during acid hydrolysis could accumulate in the waste liquid upon its recycling, we measured the changes occurring in the reducing sugar content in waste liquid after each cycle, as shown in Figure 5. The reducing sugar concentration in the unrecycled waste liquid was 1.08 g/L, and then it increased with the increase of the number of waste liquid cycles, reaching a peak value of 3.32 g/L after the third cycle. Following this point, the reducing sugar concentration decreased sharply and then remained low, presumably due to its degradation. Literature shows that the reducing sugar in waste liquids could be further degraded into organic acids, 5-hydroxymethyl furfural and other by-products [23, 24,].

Figure 5 Reducing sugar concentrations in waste liquid after a varied number of cycles.
Figure 5

Reducing sugar concentrations in waste liquid after a varied number of cycles.

The maximum observed reducing sugar concentration, 3.32 g/L, was much lower than that of 15-25 g/L required for ethanol production after conventional cellulose hydrolysis [25, 26,]. Thus, the use of accumulated reducing sugar for ethanol production is technically feasible, but not economically favorable.

3.5 Effect of waste liquid recycling on the residual metal content in hydrolyzed cellulose

MCC has strict requirements on the heavy metal content, which should not exceed 10 ppm (Pharmacopoeia of the People’s Republic of China, 2015). Figure 6 shows the metal ion concentrations in acidic waste liquid after three cycles. As can be seen, no heavy metals were detected in the hydrolyzed cellulose sample except for Au, only because the surface was sprayed with gold prior to the test.

Figure 6 EDS spectra of hydrolyzed cellulose after three waste liquid cycles.
Figure 6

EDS spectra of hydrolyzed cellulose after three waste liquid cycles.

3.6 Effects of waste liquid recycling on the yield of hydrolyzed cellulose

The yields of hydrolyzed cellulose after a varied number of waste liquid cycles are shown in Figure 7. With the increase in the number of waste liquid cycles, the yield of hydrolyzed cellulose first decreased slightly, from 92.3% to 88.7%, then increased to 91.2%. Thus, the waste liquid recycling had little effect on the main product yield.

Figure 7 Yield of hydrocellulose after several waste liquid cycles.
Figure 7

Yield of hydrocellulose after several waste liquid cycles.

3.7 Effect of waste liquid recycling on thermal stability of hydrolyzed cellulose

Figure 8 shows the TG curves of the resulting hydrolyzed cellulose after a varied number of waste liquid cycles. They all turned out to be near identical to the curve of the product obtained with fresh acid, indicating that the waste liquid recycling had no effect on the thermal stability of hydrolyzed cellulose. This information is consistent with literature stating that the thermostability of hydrolyzed cellulose is similar to that of natural cellulose, with the main change occurring at 240-400°C, when pyrolytic low-molecular-weight volatile compounds evolve [27, 28,].

Figure 8 Thermogravimetric (TG) curves of hydrolyzed cellulose after a varied number of waste liquid cycles.
Figure 8

Thermogravimetric (TG) curves of hydrolyzed cellulose after a varied number of waste liquid cycles.

3.8 Fresh acid usage

Figure 9 shows the amounts of fresh acid required for hydrolysis after a varied number of waste liquid cycles, to match the original acid concentration. As expected, the recycling of waste liquor significantly reduced the amount of fresh acid, as it was used up for hydrolysis. Yet, when the waste liquid was recycled once, twice and three times, the amounts of fresh acid required for acid hydrolysis were only 62.1%, 50.0% and 43.4% of the fresh acid amount, respectively. Therefore, waste liquid recycling can significantly reduce the production cost of hydrolyzed cellulose while also reducing the amount of waste liquid and waste water discharge, thus benefiting the environment. As shown above, this can be done without sacrificing the product quality, as long as the number of cycles does not exceed three.

Figure 9 Fresh acid required for acid hydrolysis after a varied number of waste liquid cycles.
Figure 9

Fresh acid required for acid hydrolysis after a varied number of waste liquid cycles.

4 Conclusion

Waste liquid recycling was shown to be feasible in the process of cellulose acid hydrolysis. With up to three cycles, the quality of hydrolyzed cellulose remained high. Moreover, the degree of crystallinity of hydrolyzed cellulose even increased slightly from 79.4% to 82.2%. The reducing sugar concentration in the waste liquid accumulated concomitantly, reaching the maximum value of 3.32 g/L after three waste liquid cycles, although the ethanol production was still not economically feasible with this low concentration. However, waste liquid recycling can significantly reduce the amount of fresh acid usage and waste disposal, significantly reducing the MCC production cost and contributing to environmental protection.

Acknowledgements

This research project was supported by the National Key Research and Development Plan of China (2017YFB0307901), Key Research and Development Projects of Shaanxi Province (2017ZDXM-SF-090), Research Planning Program of Key Laboratory Pulp and Paper Science &Technology of Ministry of Education of China (08031352), the Doctoral Scientific Research Foundation (Grant No. BJ13-14) of Shaanxi University of Science and Technology, and Research Plan Project (Project # 15JK1101) of Education Department of Shaanxi Province in China.

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Received: 2018-04-25
Accepted: 2018-09-13
Published Online: 2019-05-18
Published in Print: 2019-01-28

© 2019 Huijuan Xiu et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 Public License.

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  70. Biosynthetic potential assessment of four food pathogenic bacteria in hydrothermally silver nanoparticles fabrication
  71. Investigating the effectiveness of classical and eco-friendly approaches for synthesis of dialdehydes from organic dihalides
  72. Pyrolysis of palm oil using zeolite catalyst and characterization of the boil-oil
  73. Azadirachta indica leaves extract assisted green synthesis of Ag-TiO2 for degradation of Methylene blue and Rhodamine B dyes in aqueous medium
  74. Synthesis of vitamin E succinate catalyzed by nano-SiO2 immobilized DMAP derivative in mixed solvent system
  75. Extraction of phytosterols from melon (Cucumis melo) seeds by supercritical CO2 as a clean technology
  76. Production of uronic acids by hydrothermolysis of pectin as a model substance for plant biomass waste
  77. Biofabrication of highly pure copper oxide nanoparticles using wheat seed extract and their catalytic activity: A mechanistic approach
  78. Intelligent modeling and optimization of emulsion aggregation method for producing green printing ink
  79. Improved removal of methylene blue on modified hierarchical zeolite Y: Achieved by a “destructive-constructive” method
  80. Two different facile and efficient approaches for the synthesis of various N-arylacetamides via N-acetylation of arylamines and straightforward one-pot reductive acetylation of nitroarenes promoted by recyclable CuFe2O4 nanoparticles in water
  81. Optimization of acid catalyzed esterification and mixed metal oxide catalyzed transesterification for biodiesel production from Moringa oleifera oil
  82. Kinetics and the fluidity of the stearic acid esters with different carbon backbones
  83. Aiming for a standardized protocol for preparing a process green synthesis report and for ranking multiple synthesis plans to a common target product
  84. Microstructure and luminescence of VO2 (B) nanoparticle synthesis by hydrothermal method
  85. Optimization of uranium removal from uranium plant wastewater by response surface methodology (RSM)
  86. Microwave drying of nickel-containing residue: dielectric properties, kinetics, and energy aspects
  87. Simple and convenient two step synthesis of 5-bromo-2,3-dimethoxy-6-methyl-1,4-benzoquinone
  88. Biodiesel production from waste cooking oil
  89. The effect of activation temperature on structure and properties of blue coke-based activated carbon by CO2 activation
  90. Optimization of reaction parameters for the green synthesis of zero valent iron nanoparticles using pine tree needles
  91. Microwave-assisted protocol for squalene isolation and conversion from oil-deodoriser distillates
  92. Denitrification performance of rare earth tailings-based catalysts
  93. Facile synthesis of silver nanoparticles using Averrhoa bilimbi L and Plum extracts and investigation on the synergistic bioactivity using in vitro models
  94. Green production of AgNPs and their phytostimulatory impact
  95. Photocatalytic activity of Ag/Ni bi-metallic nanoparticles on textile dye removal
  96. Topical Issue: Green Process Engineering / Guest Editors: Martine Poux, Patrick Cognet
  97. Modelling and optimisation of oxidative desulphurisation of tyre-derived oil via central composite design approach
  98. CO2 sequestration by carbonation of olivine: a new process for optimal separation of the solids produced
  99. Organic carbonates synthesis improved by pervaporation for CO2 utilisation
  100. Production of starch nanoparticles through solvent-antisolvent precipitation in a spinning disc reactor
  101. A kinetic study of Zn halide/TBAB-catalysed fixation of CO2 with styrene oxide in propylene carbonate
  102. Topical on Green Process Engineering
https://doi.org/10.1515/gps-2019-0002
Schlagwörter für diesen Artikel
acid hydrolysis; waste liquid; recycling; microcrystalline cellulose
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Artikel in diesem Heft

  1. Regular Articles
  2. Studies on the preparation and properties of biodegradable polyester from soybean oil
  3. Flow-mode biodiesel production from palm oil using a pressurized microwave reactor
  4. Reduction of free fatty acids in waste oil for biodiesel production by glycerolysis: investigation and optimization of process parameters
  5. Saccharin: a cheap and mild acidic agent for the synthesis of azo dyes via telescoped dediazotization
  6. Optimization of lipase-catalyzed synthesis of polyethylene glycol stearate in a solvent-free system
  7. Green synthesis of iron oxide nanoparticles using Platanus orientalis leaf extract for antifungal activity
  8. Ultrasound assisted chemical activation of peanut husk for copper removal
  9. Room temperature silanization of Fe3O4 for the preparation of phenyl functionalized magnetic adsorbent for dispersive solid phase extraction for the extraction of phthalates in water
  10. Evaluation of the saponin green extraction from Ziziphus spina-christi leaves using hydrothermal, microwave and Bain-Marie water bath heating methods
  11. Oxidation of dibenzothiophene using the heterogeneous catalyst of tungsten-based carbon nanotubes
  12. Calcined sodium silicate as an efficient and benign heterogeneous catalyst for the transesterification of natural lecithin to L-α-glycerophosphocholine
  13. Synergistic effect between CO2 and H2O2 on ethylbenzene oxidation catalyzed by carbon supported heteropolyanion catalysts
  14. Hydrocyanation of 2-arylmethyleneindan-1,3-diones using potassium hexacyanoferrate(II) as a nontoxic cyanating agent
  15. Green synthesis of hydratropic aldehyde from α-methylstyrene catalyzed by Al2O3-supported metal phthalocyanines
  16. Environmentally benign chemical recycling of polycarbonate wastes: comparison of micro- and nano-TiO2 solid support efficiencies
  17. Medicago polymorpha-mediated antibacterial silver nanoparticles in the reduction of methyl orange
  18. Production of value-added chemicals from esterification of waste glycerol over MCM-41 supported catalysts
  19. Green synthesis of zerovalent copper nanoparticles for efficient reduction of toxic azo dyes congo red and methyl orange
  20. Optimization of the biological synthesis of silver nanoparticles using Penicillium oxalicum GRS-1 and their antimicrobial effects against common food-borne pathogens
  21. Optimization of submerged fermentation conditions to overproduce bioethanol using two industrial and traditional Saccharomyces cerevisiae strains
  22. Extraction of In3+ and Fe3+ from sulfate solutions by using a 3D-printed “Y”-shaped microreactor
  23. Foliar-mediated Ag:ZnO nanophotocatalysts: green synthesis, characterization, pollutants degradation, and in vitro biocidal activity
  24. Green cyclic acetals production by glycerol etherification reaction with benzaldehyde using cationic acidic resin
  25. Biosynthesis, characterization and antimicrobial activities assessment of fabricated selenium nanoparticles using Pelargonium zonale leaf extract
  26. Synthesis of high surface area magnesia by using walnut shell as a template
  27. Controllable biosynthesis of silver nanoparticles using actinobacterial strains
  28. Green vegetation: a promising source of color dyes
  29. Mechano-chemical synthesis of ammonia and acetic acid from inorganic materials in water
  30. Green synthesis and structural characterization of novel N1-substituted 3,4-dihydropyrimidin-2(1H)-ones
  31. Biodiesel production from cotton oil using heterogeneous CaO catalysts from eggshells prepared at different calcination temperatures
  32. Regeneration of spent mercury catalyst for the treatment of dye wastewater by the microwave and ultrasonic spray-assisted method
  33. Green synthesis of the innovative super paramagnetic nanoparticles from the leaves extract of Fraxinus chinensis Roxb and their application for the decolourisation of toxic dyes
  34. Biogenic ZnO nanoparticles: a study of blueshift of optical band gap and photocatalytic degradation of reactive yellow 186 dye under direct sunlight
  35. Leached compounds from the extracts of pomegranate peel, green coconut shell, and karuvelam wood for the removal of hexavalent chromium
  36. Enhancement of molecular weight reduction of natural rubber in triphasic CO2/toluene/H2O systems with hydrogen peroxide for preparation of biobased polyurethanes
  37. An efficient green synthesis of novel 1H-imidazo[1,2-a]imidazole-3-amine and imidazo[2,1-c][1,2,4]triazole-5-amine derivatives via Strecker reaction under controlled microwave heating
  38. Evaluation of three different green fabrication methods for the synthesis of crystalline ZnO nanoparticles using Pelargonium zonale leaf extract
  39. A highly efficient and multifunctional biomass supporting Ag, Ni, and Cu nanoparticles through wetness impregnation for environmental remediation
  40. Simple one-pot green method for large-scale production of mesalamine, an anti-inflammatory agent
  41. Relationships between step and cumulative PMI and E-factors: implications on estimating material efficiency with respect to charting synthesis optimization strategies
  42. A comparative sorption study of Cr3+ and Cr6+ using mango peels: kinetic, equilibrium and thermodynamic
  43. Effects of acid hydrolysis waste liquid recycle on preparation of microcrystalline cellulose
  44. Use of deep eutectic solvents as catalyst: A mini-review
  45. Microwave-assisted synthesis of pyrrolidinone derivatives using 1,1’-butylenebis(3-sulfo-3H-imidazol-1-ium) chloride in ethylene glycol
  46. Green and eco-friendly synthesis of Co3O4 and Ag-Co3O4: Characterization and photo-catalytic activity
  47. Adsorption optimized of the coal-based material and application for cyanide wastewater treatment
  48. Aloe vera leaf extract mediated green synthesis of selenium nanoparticles and assessment of their In vitro antimicrobial activity against spoilage fungi and pathogenic bacteria strains
  49. Waste phenolic resin derived activated carbon by microwave-assisted KOH activation and application to dye wastewater treatment
  50. Direct ethanol production from cellulose by consortium of Trichoderma reesei and Candida molischiana
  51. Agricultural waste biomass-assisted nanostructures: Synthesis and application
  52. Biodiesel production from rubber seed oil using calcium oxide derived from eggshell as catalyst – optimization and modeling studies
  53. Study of fabrication of fully aqueous solution processed SnS quantum dot-sensitized solar cell
  54. Assessment of aqueous extract of Gypsophila aretioides for inhibitory effects on calcium carbonate formation
  55. An environmentally friendly acylation reaction of 2-methylnaphthalene in solvent-free condition in a micro-channel reactor
  56. Aegle marmelos phytochemical stabilized synthesis and characterization of ZnO nanoparticles and their role against agriculture and food pathogen
  57. A reactive coupling process for co-production of solketal and biodiesel
  58. Optimization of the asymmetric synthesis of (S)-1-phenylethanol using Ispir bean as whole-cell biocatalyst
  59. Synthesis of pyrazolopyridine and pyrazoloquinoline derivatives by one-pot, three-component reactions of arylglyoxals, 3-methyl-1-aryl-1H-pyrazol-5-amines and cyclic 1,3-dicarbonyl compounds in the presence of tetrapropylammonium bromide
  60. Preconcentration of morphine in urine sample using a green and solvent-free microextraction method
  61. Extraction of glycyrrhizic acid by aqueous two-phase system formed by PEG and two environmentally friendly organic acid salts - sodium citrate and sodium tartrate
  62. Green synthesis of copper oxide nanoparticles using Juglans regia leaf extract and assessment of their physico-chemical and biological properties
  63. Deep eutectic solvents (DESs) as powerful and recyclable catalysts and solvents for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones
  64. Biosynthesis, characterization and anti-microbial activity of silver nanoparticle based gel hand wash
  65. Efficient and selective microwave-assisted O-methylation of phenolic compounds using tetramethylammonium hydroxide (TMAH)
  66. Anticoagulant, thrombolytic and antibacterial activities of Euphorbia acruensis latex-mediated bioengineered silver nanoparticles
  67. Volcanic ash as reusable catalyst in the green synthesis of 3H-1,5-benzodiazepines
  68. Green synthesis, anionic polymerization of 1,4-bis(methacryloyl)piperazine using Algerian clay as catalyst
  69. Selenium supplementation during fermentation with sugar beet molasses and Saccharomyces cerevisiae to increase bioethanol production
  70. Biosynthetic potential assessment of four food pathogenic bacteria in hydrothermally silver nanoparticles fabrication
  71. Investigating the effectiveness of classical and eco-friendly approaches for synthesis of dialdehydes from organic dihalides
  72. Pyrolysis of palm oil using zeolite catalyst and characterization of the boil-oil
  73. Azadirachta indica leaves extract assisted green synthesis of Ag-TiO2 for degradation of Methylene blue and Rhodamine B dyes in aqueous medium
  74. Synthesis of vitamin E succinate catalyzed by nano-SiO2 immobilized DMAP derivative in mixed solvent system
  75. Extraction of phytosterols from melon (Cucumis melo) seeds by supercritical CO2 as a clean technology
  76. Production of uronic acids by hydrothermolysis of pectin as a model substance for plant biomass waste
  77. Biofabrication of highly pure copper oxide nanoparticles using wheat seed extract and their catalytic activity: A mechanistic approach
  78. Intelligent modeling and optimization of emulsion aggregation method for producing green printing ink
  79. Improved removal of methylene blue on modified hierarchical zeolite Y: Achieved by a “destructive-constructive” method
  80. Two different facile and efficient approaches for the synthesis of various N-arylacetamides via N-acetylation of arylamines and straightforward one-pot reductive acetylation of nitroarenes promoted by recyclable CuFe2O4 nanoparticles in water
  81. Optimization of acid catalyzed esterification and mixed metal oxide catalyzed transesterification for biodiesel production from Moringa oleifera oil
  82. Kinetics and the fluidity of the stearic acid esters with different carbon backbones
  83. Aiming for a standardized protocol for preparing a process green synthesis report and for ranking multiple synthesis plans to a common target product
  84. Microstructure and luminescence of VO2 (B) nanoparticle synthesis by hydrothermal method
  85. Optimization of uranium removal from uranium plant wastewater by response surface methodology (RSM)
  86. Microwave drying of nickel-containing residue: dielectric properties, kinetics, and energy aspects
  87. Simple and convenient two step synthesis of 5-bromo-2,3-dimethoxy-6-methyl-1,4-benzoquinone
  88. Biodiesel production from waste cooking oil
  89. The effect of activation temperature on structure and properties of blue coke-based activated carbon by CO2 activation
  90. Optimization of reaction parameters for the green synthesis of zero valent iron nanoparticles using pine tree needles
  91. Microwave-assisted protocol for squalene isolation and conversion from oil-deodoriser distillates
  92. Denitrification performance of rare earth tailings-based catalysts
  93. Facile synthesis of silver nanoparticles using Averrhoa bilimbi L and Plum extracts and investigation on the synergistic bioactivity using in vitro models
  94. Green production of AgNPs and their phytostimulatory impact
  95. Photocatalytic activity of Ag/Ni bi-metallic nanoparticles on textile dye removal
  96. Topical Issue: Green Process Engineering / Guest Editors: Martine Poux, Patrick Cognet
  97. Modelling and optimisation of oxidative desulphurisation of tyre-derived oil via central composite design approach
  98. CO2 sequestration by carbonation of olivine: a new process for optimal separation of the solids produced
  99. Organic carbonates synthesis improved by pervaporation for CO2 utilisation
  100. Production of starch nanoparticles through solvent-antisolvent precipitation in a spinning disc reactor
  101. A kinetic study of Zn halide/TBAB-catalysed fixation of CO2 with styrene oxide in propylene carbonate
  102. Topical on Green Process Engineering
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