Biocatalysis is a growing field in the production of fine chemicals and will most probably increase its share in the future. Enzymatic reactions are carried out under mild conditions, i.e., non-toxic solvents, low temperature and pressure, which eliminates most environmental drawbacks associated with conventional production methods. The superiority of chemo-, regio-and enantioselectivity of enzymes exhibit significant advantages over conventional catalysts for production of fine chemicals, flavors, fragrances, agrochemicals and pharmaceuticals. Enzymes can function both in aqueous and non-aqueous solvents. As a result of the growing scientific and industrial interest towards green chemistry, green solvent systems, which are mainly water, supercritical fluids, ionic liquids, fluorinated solvents, and solvent-free systems have become more popular in biocatalysis. However, the activity and selectivity of an enzyme is heavily dependent on solvent properties. In this review, various green solvents were classified and some of their influential features on enzyme activity were discussed.
a b s t r a c tThe feasibility of using activated carbon/chitosan-poly (vinyl alcohol) biocomposites (AC/CHT-PVA) as an adsorbent for removal of naproxen from a factory wastewater in Tuzla, Istanbul/Turkey was studied in the presented study. The biocomposites were synthesized with different AC: CHT-PVA ratios of 1.0; 2.0 and 3.0 (w/w). The adsorbent materials were characterized by FT-IR, SEM and TGA analysis. When AC was embedded into CHT-PVA matrix, the naproxen removal performance increased from 41.01% to 97.03%. The optimal pH for maximum adsorption was found as 7.0. Equilibrium isotherms for the naproxen adsorption onto AC/CHT-PVA biocomposite were measured experimentally. The Langmuir model was fitted to the equilibrium data better than The Freundlich, Temkin and Dubinin-Raduskevich isotherm models. The mono layer adsorption capacity of AC/ CHT-PVA:3.0 for naproxen was found to be 12.24 mg/g at 298 K. According to the kinetics results, the equilibrium time of AC/CHT-PVA biocomposites was found 100 min and it was indicated that the adsorption follows the pseudo second-order kinetic model. The process was favorable and spontaneous. The thermodynamic parameters, ΔG°, ΔS° and ΔH° were calculated and the enthalpy of adsorption (ΔH°) was found positive for all biocomposites supported the endothermic nature of adsorption reactions.
AbstractIn the present study, activated carbon/alginate (AC/ALG) beads were successfully synthesized with different AC:ALG ratios of 1.0–3.0 (w/v) and used for the adsorption of the nonsteroidal anti-inflammatory drug naproxen from wastewater. The beads were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analysis, and adsorbent dosage, initial pH, initial naproxen concentration, and contact time in removal efficiency were investigated. Maximum naproxen removal percentage was achieved using 350 mg of AC/ALG beads with a ratio of 3.0% (w/v) within six hours and naproxen removal performance was determined to be 98.0%. Freundlich, Temkin, and Dubinin–Radushkevich (D-R) isotherm models were fitted to the equilibrium data better than the Langmuir model. According to kinetics results, the equilibrium time for the AC/ALG beads was reached in four hours and the kinetic model was determined by the pseudo-second-order equation. The thermodynamic parameters were calculated and enthalpy of naproxen adsorption was found to be positive for all AC/ALG beads. After the adsorption process the beads can easily be regenerated by ethanol and reused within seven cycles.
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