Lima Rose Miranda

Chemical activation of Artocarpus heterophyllus Lam (jackfruit peel) via phosphoric acid was focused on this study for the preparation of activated carbon. Carbonization was done at a temperature of 400°C based on the nature of biomass after the impregnation ratio of 1 : 1 (weight of phosphoric acid/weight of raw material). Titanium dioxide was doped on the prepared activated carbon through the sol-gel method. Titanium dioxide doped activated carbon was synthesized to perceive the nature of adsorbents under ambient conditions. Both JPAC and JPAC/TiO₂ adsorbents were characterized by the point of zero charges, Fourier transform of infrared spectroscopy, X-ray diffraction spectroscopy, Brunauer-Emmett-Teller analysis, and scanning electron microscopy with energy-dispersive X-ray analysis. The adsorption capacity of Reactive Red 194 (Red 2BN) dye on jackfruit peel activated carbon (JPAC) is 32.271 mg/g, and JPAC/TiO₂ is 34.900 mg/g was observed under optimum conditions. Desorption efficiency of JPAC/TiO₂ (≥93.4%) is slightly higher compared to JPAC (≥89.2%). Tannery effluents of various parameters were analyzed, and their chemical oxygen demand (COD) values trim down within the permissible limits of JPAC (97%) and JPAC/TiO₂ (98%). Experimental data were studied using both two-parameter and three-parameter models of adsorption isotherm, namely, the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Redlich-Peterson, Sips, Toth, and Khan. In which the Langmuir isotherm ([ ]) best described the experimental data with an optimum monolayer capacity for adsorption capacity of 49.7 mg/g at 323 K on Red 2BN molecules. A proposed scheme of Red 2BN molecules on the active sites of adsorbents was illustrated. Regeneration of spent carbons was studied through different cycles of the run.

Pyrolysis processes were investigated using expanded polystyrene waste (EPW) with a catalyst synthesized from rice husk (RH). Biomass was treated with different acids, i.e., sulfuric acid, oxalic acid, and hydrochloric acid. The effect of normality on the oxalic acid-treated catalyst and the effects of polymer to catalyst ratio on (i) oil, gas, and residues yields; (ii) temperature; and (iii) time for the complete reaction were investigated for the effective use of oil for fuel production. The catalyst treated with 0.25 N (RH_OA0.25) resulted in a high oil yield of 96 wt% and a residue yield of 3.47 wt%. The oil produced contained mainly aromatic compounds, which contributed 67.86% in an area-based GC-MS analysis. The synthesized catalyst showed a stable capacity for three regeneration runs. The significant factor is that the synthesized catalyst decreased the activation energy during the pyrolysis of EPW.

Graphene oxide/chitosan and reduced graphene oxide/chitosan (GO/CS and RGO/CS) beads were prepared by precipitation with NaOH. Porcine liver esterase was immobilized on these beads to give GO/CS/E and RGO/CS/E beads. The optimum conditions for the maximum activity of RGO/CS/E beads were pH 8 and 50°C. The stability of the enzyme immobilized on GO/CS/E and RGO/CS/E was high in the pH range of 5–8. The GO/CS/E beads showed superior stability compared to that of the free enzyme and CS/E beads between 20 and 50°C. Kinetic analysis showed that GO/CS/E was a better catalyst than the RGO/CS/E beads with a lower K_m value of 0.9 mM. The hybrid beads also retained more than 95% activity after 10 consecutive cycles. The GO/CS/E and RGO/CS/E beads retained 84% and 87% activity after 40 days at 4°C. The GO/CS/E beads were used for the successful hydrolysis of methyl 4-hydroxy benzoate.

This research involves the optimization of different variables of the operating conditions to prepare activated carbon from pomegranate peels (Punica granatum peel). For this purpose, a statistical method called Response Surface Methodology (RSM) has been adopted to economize the number of experiments and their meaningful interpretation. Activated carbon was produced by chemical activation (H₃PO₄). RSM was used to evaluate the variables considered in the preparation of activated carbon such as impregnation ratio (2–4 g H₃PO₄/g pomegranate peel), temperature (400–600°C), and activation time (30–90 min), experimented using a three-variable Box–Behnken Design (BBD) based on a quadratic model and an RSM tool provided by Design Expert 8.0.4 (STAT-EASE Inc., Minneapolis, USA). The responses analyzed for optimization were the methylene blue number and the iodine number. The factors that are significant influencing the activated carbon preparation have been identified by an analysis of variance (ANOVA). The optimum conditions established were impregnation ratio of 2.78, activation temperature of 575°C, and activation time of 73 min.