Volume 23, Issue 4

Hospital plastic waste poses significant challenges due to its volume, hazardous nature, and environmental persistence. This review consolidates recent advancements in the pyrolysis of hospital plastic waste, evaluating its feasibility as a sustainable solution within healthcare waste management systems. Findings reveal that pyrolysis offers high oil yields when optimized for key operational parameters – specifically temperatures between 400 and 500 °C, moderate heating rates, and residence times tailored to specific plastic types. The review identifies polypropylene and polyethylene as the most suitable hospital-derived plastics for pyrolysis, though the presence of contaminants, such as PVC or biological residues, can significantly hinder process efficiency and environmental compliance. Emerging studies demonstrate that upgrading pyrolysis oil quality and utilizing byproducts like char and syngas can improve the overall economic and ecological performance of the process. Furthermore, integration of pyrolysis into hospital waste management systems is technically feasible and scalable, especially when supported by pre-sorting protocols and decentralized processing units. The review concludes that pyrolysis, when appropriately managed and regulated, can contribute to a circular economy by converting hazardous plastic waste into energy resources while minimizing environmental impact. These findings support the implementation of pyrolysis as a green and economically viable technology, encouraging policy frameworks and infrastructure investment to promote its adoption in healthcare facilities.

A hybrid Proportional-Integral-Derivative Model Predictive Controller (PID-MPC) is developed to regulate the temperature of a batch reactor to obtain high yield of product in the novel production of magnesium stearate from magnesium hydroxide and palm stearin, with palm stearin serving as a sustainable, renewable alternative to existing source of stearic acid. Previous studies indicate that a reaction temperature of 180 °C yields an optimum yield of magnesium stearate highlighting the critical role of precise temperature control in optimizing reactor performance. In this study, a PID controller was initially tuned using the Ziegler-Nichols (ZN) method, yielding proportional, integral, and derivative gains of 0.6, 3.75, and 0.024, respectively. The MPC design was then integrated with the PID controller, utilizing a prediction horizon of 60, a control horizon of 20, and a sampling time of 0.216 s. Simulations were conducted using MATLAB R2024a’s Simulink toolbox to evaluate the performance of the hybrid PID-MPC controller in comparison to single PID and MPC controllers in both servo and regulatory cases. The hybrid PID-MPC controller outperformed the standalone PID and MPC controller in the absence of process disturbance, demonstrating minimal overshoot and a faster settling time. While the Mean Absolute Error (MAE) and Mean Squared Error (MSE) for both the hybrid PID-MPC and single MPC controllers were similar where both approaching to zero. In the presence of constraint, it excelled in disturbance and noise rejection, achieving the lowest MAE (1.245) and MSE (1.551), highlighting its superior robustness and control performance compared to single controllers ensuring high quality and yield of magnesium stearate of 68.16 % using palm stearin. These findings demonstrate that the hybrid PID-MPC approach provides highly robust and efficient temperature control, even under the influence of disturbances, positioning it as a great solution for enhancing the performance and optimization of batch reactor operations in producing high yield of magnesium stearate using renewable palm stearin.

A novel Schiff-base derivative, PNOL, incorporating pyridine and naphthalene moieties, was synthesized and characterized using 1 H NMR, 13 C NMR, FTIR, and UV–Vis spectroscopy. The UV–Vis spectral behavior of PNOL was investigated under varying solvent, pH, and concentration conditions, revealing its significant sensitivity to environmental factors. The ligand demonstrated excellent selectivity and sensitivity for Fe 3+ , Fe 2+ , and Cu 2+ ions, with distinct colorimetric responses visible to the naked eye. Upon metal ion binding, blue shifts in absorbance were observed at 82 nm for Cu 2+ , 48 nm for Fe 3+ , and 54 nm for Fe 2+ , along with an isosbestic point at ∼380 nm, confirming complex formation. Job’s plot analysis established 2:1 and 1:1 binding stoichiometries for Fe 3+ and Cu 2+ , respectively, while Fe 2+ exhibited a 1:1 complex formation. The binding constants determined for Fe 2+ , Fe 3+ , and Cu 2+ were 0.56 × 10 7  M −1 , 0.35 × 10 7  M −1 , and 0.64 × 10 7  M −1 , respectively, with LOD values as low as 2.4 × 10 −8  mg/L (Fe 2+ ), 5 × 10 −8  mg/L (Fe 3+ ), and 6.7 × 10 −8  mg/L (Cu 2+ ), surpassing previously reported sensors. The observed spectral shifts were attributed to ligand-to-metal charge transfer (LMCT) and internal charge transfer (ICT) interactions, inhibiting C=N isomerization. These findings establish PNOL as an efficient and selective colorimetric sensor for Fe 3+ , Fe 2+ , and Cu 2+ ions, with potential applications in environmental monitoring, analytical chemistry, and biosensing.

Vanadium-doped black TiO 2 nanoparticles were synthesized by modified sol-gel method. The characterisation of vanadium doped black TiO 2 nanoparticles was carried out using DRS, XRD, and SEM with EDX analysis to determine band gap energy, crystal structure, surface morphology and elemental composition. The nanoparticles were coated on pre cleaned glass beads by dip coating technique. Methylene blue was employed as a model dye to determine the photo-catalytic efficiency of vanadium doped black TiO 2 nanoparticles. The photo-catalytic degradation of aqueous methylene blue dye was performed in packed re-circulated photo reactor. The band gap energy of 4 wt% vanadium doped black TiO 2 nanoparticles was found to be 2.04 eV, the least among the synthesised nanoparticles. Various degradation process parameters like flow rate, initial concentration of dye and volume of dye were also determined. About 98 % methylene blue dye photo-catalytic degradation was achieved under visible lamp (300 W) illumination for 4.0 wt% vanadium doped black TiO 2 photo-catalyst under optimum conditions.

This study investigates the degradation of Orange II (ORII), a model azo dye, in water using a natural clay (NC)/Oxalate/UVA-Vis system via a heterogeneous photo-Fenton-like (HPF-like) process. Iron-rich natural clay acts as a sustainable photocatalyst in the presence of oxalic acid (OA) under UVA-Vis irradiation (366 nm) at free pH and ∼25 °C. Characterization (SEM-EDS, TEM, XRF, BET) confirmed 26.3 % iron content and a 52.66 m 2  g −1 surface area. ORII photodegradation (0.1 mM) in 1 g L −1  NC was enhanced by 5 mM oxalic acid, following first-order kinetics (t 1 / 2  ≈ 20 min) with 90 % removal after 2 h. The combined effect of UVA-Vis irradiation and the surface formation of ferrioxalate complexes facilitated the photoinduced reduction of iron, leading to its dissolution and the generation of hydroxyl radicals (HO · ) via a Fenton-like cycle, which were primarily responsible for ORII degradation. A synergistic effect was observed when H 2 O 2 was introduced further enhancing HO · radical formation. The NC/OA/UVA-Vis system exhibited degradation behavior similar to that of goethite and proved to be a cost-effective, eco-friendly method for pretreating water contaminated with azo dyes.

Sustainable and ecologically friendly discharge of slaughterhouse wastewater requires effective treatment. The chicken slaughter house wastewater (CHSW) samples exhibited elevated organic contents with the chemical oxygen demand (COD) (2,111.33 ± 31.63 mg L −1 ), total organic carbon (TOC) (717.64 ± 31.63 mg L −1 ), biological oxygen demand (BOD 5 ) (1,350 ± 24.49 mg L −1 ), ammonical-N (77.03 ± 0.24 mg L −1 ), phosphate (4.05 ± 0.02 mg L −1 ) and TSS (833 ± 12.72 mg L −1 ). The present research investigated the treatment of CHSW using biochar, derived from a market waste (waste corncob), employing H 3 PO 4 as the impregnating agent in the carbonization process. The removal of TOC, COD, phosphate, BOD 5 , and ammoniacal-N were found as 85 ± 5 %, 84.51 ± 2.32 %, 15.70 ± 0.23 %, 79.54 ± 2.27 %, and 74.03 ± 1.11 % respectively, when 40 mL CHSW was treated with 5 g L −1 biochar (size: 253 μm) for 120 min at its own pH. A 2-D transient convective-diffusive model based on a numerical method was employed and validated. A single-factor local sensitivity analysis was also conducted using the relative marginal value (RMV).

The combustion of hydrocarbon fuels is a complex chemical reaction process. In this study, the effects of various H 2 –NH 3 blending ratio ( α ) in CH 4 /H 2 /NH 3 ternary fuel on laminar burning velocity (LBV), CO 2 , NOx, adiabatic flame temperature, and temperature sensitivity were investigated using Chemkin/Premix code. The results showed that α exerted more pronounced effects on LBVs of ternary fuel compared to the hydrogen volume fraction in the H 2 –NH 3 mixture ( β ). Fuel-rich combustion effectively reduced NOx emissions, compared to experiments of pure NH 3 blending, and the H 2 –NH 3 mixture significantly reduced NOx emissions in ternary premixed flames when equivalence ratios ( Φ ) exceeded 1.0. Temperature sensitivity analysis revealed that reaction R318 (NH 2  + O <=> HNO + H) exhibited temperature inhibition. This observation elucidated the initiation of the NH 2 → HNO → NO → N 2 O → N 2 pathway and demonstrated that C–N reactions were negligible in predicting laminar combustion characteristics of CH 4 /H 2 /NH 3 ternary fuel.

This work presents the mixing conditions and kinetic reaction constant effects on a continuous stirred tank reactor (CSTR) consecutive-parallel reactions selectivity dynamics in an isothermal CSTR based on Cholette’s model. The mixing condition effect is accounted for using the parameter μ  =  n / m , where n is the flow fraction to the reactor and m is the dead space fraction in the reactor. μ  = 1 and μ ≠1 represent, respectively, the ideal and nonideal mixing operations. The final desired product yield steady state in the phase plane is first constructed under reaction constant and mixing condition combinations, μ  = 0.5, μ  = 1 and μ  = 2. The simulation results reveal that the larger the μ parameter, the higher the reactant final steady state values, a s , and the desired product, b s . For μ  = 0.5 < 1, the short circuit flow or channeling effects were less than that of the dead volume in a real CSTR, leading to lower both final steady state values, a s and b s , than those under ideal mixing, μ  = 1. On the other hand, under the nonideal mixing condition μ  = 2 > 1, i.e., the short circuit flow effect or channeling larger than the dead volume in the reactor, resulted in a higher final steady state ( a s , b s ) than those under ideal mixing. A comparative analysis of the mixing condition effects reveals that a higher μ value reduces the transient maximum selectivity regions while increasing the transient minimum selectivity regions. In the selectivity dynamic simulations, the phase plane is divided into a transient extreme yield region and monotonic yield variation region. It is observed, for the first time, that a higher μ value diminishes the transient maximum selectivity region area while expanding the transient minimum selectivity region area in the phase plane. Additionally, the trajectory from the start up to the final steady state is altered due to nonideal mixing. These novel findings, which have not been previously published, hold direct relevance for the design and operation of real reactors. Given that ideal mixing is rarely achievable in practical CSTRs, our results offer valuable insights for optimizing reactor design and start-up policies to enhance the desired product transient yield.

Protecting water resources is vital for our future. Improved treatment methods can ensure safe and sustainable water for generations to come. With growing populations and climate change, efficient water management also boosts economic savings across industries. In this study, a one-factorial approach was employed to determine the optimal conditions for the removal of Malachite Green (MG) dye. Additionally, efforts were made to incorporate various processes to enhance performance after identifying the optimal conditions. The results obtained from the UV/PAC-Fe 3 O 4 /UV H 2 O 2 processes were compared. In this research, analyses related to LC/MS, SEM, EDX, and kinetic plots were also reported to evaluate the performance of the processes. Findings indicated that the use of the nanocomposite and UV treatment achieved the highest efficiency in removing MG dye from aqueous solutions (74 %). Furthermore, the simultaneous application of these two processes can reduce the required time for the treatment. Additionally, results from LC/MS demonstrated that the compounds generated from this process ultimately convert into carbon dioxide and water molecules. The kinetics associated with this process were determined to be pseudo-first-order, with the highest R 2 value (0.9691). Among the various methods evaluated, the final process, UV/PAC-Na 2 S 2 O 8 /UV/H 2 O 2 demonstrated the highest removal efficiency and may be considered a promising approach for application in the textile industry.