Volume 7, Issue 4

This case study investigates low-energy alternatives to distillation for the recovery of N-methyl-2-pyrrolidone (NMP) from solvent waste in the manufacture of resin precursors. Evaluation includes environmental and economic life cycle assessment of solvent recovery and reuse using batch distillation, solvent extraction, and solvent extraction at a sister plant. Solvent extraction at the sister plant involved shipment of hazardous waste to a facility with existing solvent recovery equipment and lower purity standards for NMP. The amount of processing required to recover useful NMP is reduced, increasing reductions in life cycle emissions and damages to the environment. Extraction at the sister plant recovered 98% of the NMP at a purity of 97.1 wt% from aqueous waste containing 17 wt% NMP. Extraction at the sister plant reduced total and CO 2 life cycle emissions by 61% and 59%, respectively. Compared to the distillation recovery alternative, extraction at the sister plant results in reductions of 32% and 33% for total and CO 2 life cycle emissions, respectively. Annual operating costs were reduced by 80%, with no capital investment, due to utilization of existing equipment. This resulted in a 10-year net present value (NPV) of $4.20 million, whereas distillation resulted in a 10-year NPV of $3.12 million.

The increasing interest in the development of new environment-friendly solvents has led to the synthesis of new materials that minimize the impact of solvents on the environment. However, most of the published studies on green solvents focus primarily on their physicochemical properties, with limited emphasis on their toxicological risk in the environment. In this study, the acute toxicities of five ionic liquids, 1-propylpyridinium tetrafluoroborate, 1-butylpyridinium tetrafluoroborate, 1-butyl-2-methylpyridinium tetrafluoroborate, 1-butyl-3-methylpyridinium tetrafluoroborate and 1-butyl-4-methylpyridinium tetrafluoroborate, on Vibrio fischeri and Daphnia magna are evaluated. In the latter bioassay, the presence and position of a methyl group on the pyridinium ring or the length of the chain attached to the nitrogen atom seem to be the key factors for toxicity. In the Vibrio fischeri study, the alkyl chain attached to the nitrogen atom has a considerable influence on EC 50 values. Moreover, quantitative structure activity relationship studies are performed to relate their physicochemical properties with their acute toxicity.

This work is devoted to the study of the cationic ring opening polymerization of tetraphenyltetramethylcyclotetrasiloxane (D 4 Ph,Me ), using a solid green catalyst prepared by the activation of a natural clay by sulfuric acid (Maghnite-H + ). This treatment leads to the spacing of the montmorillonite sheets due to the substitution of the existing interlayer cations by the protons of the acid. This consequence is clearly shown on the X-ray diffraction (XRD) spectrum. The polymerization reaction proceeded in bulk and under mild conditions. Various tests were carried out by changing the temperature, the time and the catalyst mass content in order to increase, at the same time, the yield of the reaction and the average molecular mass of the polyphenylmethylsiloxane (PPMS) obtained. The structure of the PPMS obtained was identified by infrared (IR), 1 H nuclear magnetic resonance (NMR) and 13 C NMR analyses over different periods of time. The thermal behavior was investigated by differential scanning calorimetry (DSC) analysis. At the end, in order to show the role played by the Maghnite-H + during the various reaction stages, a reaction mechanism was proposed.

CuFeS 2 nanoparticles have been synthesized and used as catalyst for the degradation of lignin. Under mild condition of reaction at 60°C and 5 h in the presence of 2 ml hydrogen peroxide, lignin can be degraded completely and converted to dicarboxylic acids, such as oxalic acid (OA), fumaric acid, maleic acid, and succinic acid (SA), carbon oxides, and aromatic compounds. The major product is OA (up to 30% selectivity) and SA. On the basis of the chemicals detected, we proposed a logical mechanism similar to Fenton reaction. The results reveal that HO˙ and HOO − , formed from the cleavage of hydrogen peroxide over the catalyst, play an essential role in the oxidation of lignin to destroy its aromatic structure and generate carboxylic or DCA. This is a potential method to convert native lignin as a renewable feedstock to produce valuable chemicals.

A series of pentasubstituted 4 H -pyrans and tetrahydrobenzo[ b ]pyrans are synthesized with excellent yields via a one-pot condensation of aromatic aldehydes, malononitrile, and a dicarbonyl compound, ethyl acetoacetate, acetyl-acetone or dimedone, in the presence of 4 Å molecular sieve modified with zinc(II) as heterogeneous catalyst, in ethanol. The process offers numerous advantages, such as better yield, short reaction time, and mild reaction conditions. The catalyst’s preparation is simple and it could be reused while still maintaining its activity.

Glycerin (glycerol) is a co-product of biodiesel production that is widely produced and is available at a low cost. To date, various applications have been investigated and introduced for biodiesel glycerin. In this study, a number of valuable products were produced using biodiesel glycerin and formic acid as the main reactants. Allyl alcohol is one of the valuable chemicals produced from glycerin monoformate. Efficient production of this product requires successful completion of the first section of the reaction, which is an equilibrium reaction. The highest feasible yield achieved was about 83% (based on the consumption of formic acid) at 120–140°C without the addition of any catalysts. Also, the esterification reaction was further investigated at room temperature, where the equilibrium state was reached with a yield of 55% after only 4 h. Moreover, the addition of urea to the reaction with the aim of producing the other two side products, i.e. diformyl urea and glycerin carbonate, in addition to glycerin monoformate, was studied. The results showed that considerable amounts of applicable byproducts, e.g. formamid, are also produced, making the process even more economical.

A sealed wet curing design on sulfating Sorghum vinegar residue waste is drilled with sulfo/sulfoalkyl chemicals. Sulfation degrees in the case of reactions with sulfuric acid, sodium sulfite, sulfamic acid, benzenesulfonic acid, p -toluenesulfonic acid and sodium laurilsulfate range from 14.7 to 36.9 mg sulfo per gram waste. The C–O–S formation gives rise to accessional noncrystallinity and mesoporosity of morphology, a character for potential alternatives in catalysis. Waste sulfates are employed as candidates in catalyzing the condensation of α-glycolic acid and urea substitutes for yielding imidazolidine-2,4-dione derivatives. Catalytic and specific activities in terms of derivative productions are 2.6–34.3 (×10 3 U) and 0.8–5.4 U/mg sulfo, together with the maximal yields of 49.4%–97.6%. Chemical linkage of sulfo/sulfoalkyl groups manifests synergism with intrinsic acidity of waste with respect to catalysis. A rational design of green chemistry is guaranteed by no excess of chemicals and easy recyclability of catalysts.

The present study was aimed at evaluating the performance of human hair as adsorbents for methylene blue (MB) dye removal. Human hair was treated using 0.1 m potassium hydroxide (KOH) and 0.1 m nitric acid, and the adsorbents were characterized for specific surface area and surface chemistry. The basic-treated human hair adsorbent (BH) exhibits a specific surface area of 3.51 m 2 /g, which is relatively higher than the acid-treated (AH) and untreated (UH) counterparts. The equilibrium data of all adsorbents obeyed the S-shaped isotherm, suggesting a cooperative adsorption. The BH displays a maximum capacity of 13.5 mg/g, while a comparable capacity of 3.4 mg/g was recorded by AH and UH. The adsorption of MB by BH increased with increasing pH. Based on the equilibrium and kinetics data, the adsorption of MB onto BH is proposed to have the following mechanisms: (i) external diffusion, (ii) intraparticle diffusion, and (iii) cooperative adsorption. In addition, the MB adsorption at a concentration of 20 mg/l is endothermic and spontaneous with temperature increasing from 35°C to 55°C. A basic treatment of human hair using KOH yields a promising adsorbent for dye in wastewater treatment.

Ionic liquids (ILs) are considered to be green solvents for various applications. However, their synthesis via chemical reaction with by-products or waste produced is contradictory to the concept of green chemistry, and the purity problem and economic feasibility limit their applications in some large-scale industrial applications. 1-Butyl-1-methylpyrrolidinium bromide ([bmpy][Br]), which is a molten salt with melting point above 100°C is a precursor of pyrrolidinium ILs, but hardly can be put under the category of IL because of its high melting point. In this study, [bmpy][Br] based binary deep eutectic solvent (BDES) and ternary deep eutectic solvent (TDES) were synthesized to prepare [bmpy][Br] in liquid form. During the preparation process, no reaction media was employed, no by-product was generated, and no further purification was required, thereby making it a completely green process. The prepared TDES has better thermal stability and larger free volume than BDES, which is potentially useful for sorption applications with high temperature requirement. It is also because of the green preparation process that the TDES is also expected to be capable for the large-scale industrial applications. This work is opening up new avenues for the study of binary and ternary IL-DES system and their applications.

Rare-earth cerium (Ce)-doped zinc oxide (ZnO) spherical nanoparticles were synthesized by using the co-precipitation method. The doped materials were characterized by means of the X-ray diffraction, Williamson-Hall Plot, and field emission scanning electron microscopy analyses. The prepared nanoparticles exhibit a hexagonal wurtzite structure as observed from the XRD measurements. Energy dispersive X-ray spectroscopy data confirmed the purity of the prepared samples. The photocatalytic activity of the rare-earth Ce-doped ZnO spherical nanoparticles was investigated through the degradation of methylene blue (MB) and p-nitrophenol (PNP) solution under UV light radiation. Among the different amounts of dopant, 5 mole% Ce-doped ZnO nanoparticles showed the highest degradation with UV light radiation for both MB dye and PNP solution. The particle size, morphology, and separation of the photo-induced electron–hole pair are the main factors that influence photocatalytic activity. The probable mechanisms of photocatalytic degradation and mineralization of MB and PNP are also explained by liquid chromatography–mass spectrometry analysis.

A green synthesis method of silver nanoparticles (AgNPs) using Centaurea virgata Lam. extract and the isolated compound eupatorin was investigated in this study. Ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM)/energy-dispersive X-ray (EDX) spectroscopy, thermal gravimetric analysis, X-ray diffraction analysis and zeta potential were used for characterization of AgNPs. The UV-Vis spectrum exhibited a characteristic absorption band at 420 nm for monodisperse nanoparticles. FTIR measurements also proved the formation. X-ray diffraction patterns showed peaks at (110) and (112), which are characteristic for hexagonal crystals and also showed peaks at (111), (200) and (240), which are characteristic for orthorhombic crystals. The TEM images of AgNPs show that the morphology of AgNPs was predominantly spherical. Obtained AgNPs were highly stable according to the zeta potential values. The nitric oxide scavenging activity, which is also related to anticancer activity, of AgNPs was evaluated. It can be concluded that C. virgata Lam. extract and eupatorin can be used as a reducing agent for potential antioxidant AgNP formation.

The kinetic studies performed on the forward extract of cerium(III) from chloride solution with the complex agents, citric acid (H 3 Cit) and lactic acid (HLac) in the presence of di-(2-ethylhexyl)phosphoric acid (D2EHPA, H 2 A 2 ) have been investigated using a constant interfacial area cell with laminar flow. The effects of stirring speed, temperature, and specific interfacial area on the extraction rate are discussed separately, and the results show that the extraction process is a diffusion-controlled kinetics process with an interfacial reaction. Studies on the effect of pH value and H 2 A 2 concentration on the extraction rate are used to obtain the rate equation. The rate-controlling step is also suggested by the predictions derived from the interfacial reaction models, and the rate equation obtained by the kinetic model is consistent with that obtained by the experimental results. The information on the extraction kinetics in this extraction system will provide some knowledge of its application.