Catalytic activity of acid-treated biomass for the degradation of expanded polystyrene waste

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. Graphical abstract.

Surfactant modified ZnO-Bi2O3 nanocomposite for degradation of lambda- cyhalothrin pesticide in visible light: A study of reaction kinetics and intermediates

Coupling of semiconductor photocatalyst attracted more attention in the area of heterogeneous photocatalytic process. Herein we developed a low-cost visible light responsive coupled ZnO-Bi₂O₃ semiconductor with a molar ratio of 1:4, 1:2, and 3:4 by facile one-step hydrothermal method using a surfactant. The influences of Bi₂O₃ content on coupled catalyst were investigated. The synthesized catalysts were characterized by X-Ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectrum (FT-IR), UV-Vis diffuse reflectance (UV-DRS). Photocatalytic performance of ZnO-Bi₂O₃ was investigated using Lambda-Cyhalothrin (L-CHT), a pyrethroid pesticide that is harmful to human beings and animals under visible light irradiation. Kinetic study of the degradation of L-CHT reveals that there is a shift in the reaction order from first-order to second-order. The photocatalytic degradation of L-CHT using ZnO-Bi₂O₃ is found to be more efficient since the separation of photogenerated holes and electrons are improved by coupling of ZnO with Bi₂O₃. When compared to bare ZnO the degradation percentage of 85.7% was achieved within 120 min of the photocatalytic process using the catalyst dosage of 1.2 gm/L in 50 mg/L of L-CHT solution with formation of Phthalic acid, butyl 2-ethyl butyl ester and Diethyl phthalate as intermediates. No other hazardous intermediates are formed and a scheme for photodegradation pathway was proposed.

Pyrolysis of polystyrene waste in the presence of activated carbon in conventional and microwave heating using modified thermocouple

Pyrolysis process was experimented using two types of heating source, namely conventional and microwave. Polystyrene (PS) plastic waste was used as feedstock in a batch reactor for both the conventional (slow pyrolysis) and microwave pyrolysis. The effect of activated carbon to polystyrene ratio on (i) yield of oil, gas and residues (ii) reaction temperature (iii) reaction time were studied. Quality of oil from pyrolysis of polystyrene were assessed for the possible applicability in fuel production. Microwave power of 450 W and polymer to activated carbon ratio of 10:1, resulted in the highest oil yield of 93.04 wt.% with a higher heating value of 45 MJ kg^-1 and a kinematic viscosity of 2.7 cSt. Microwave heating when compared to conventional heating method, exhibits a reaction temperature and time of 330 °C in 5.5 min, whereas in conventional heating system it was 418 °C in 60 min. The gas chromatography-mass spectrometry analysis of liquid oil from microwave pyrolysis predominantly yields alkenes of 8.44 wt.%, α-methyl styrene 0.96 wt.%, condensed ring aromatics 23.21 wt.% and benzene derivatives 26.77 wt.% when the polystyrene to activated carbon ratio was 10:1. Significant factor of using microwave heating is the amount of energy converted (kWh) is lesser than conventional heating.

Electrochemical degradation of specialty chemical industry effluent

Conventional wastewater treatment techniques are inefficient to manage large quantities of refractory organics discharged by specialty chemical industries. It is aimed in the present investigation to compare overall performance of the basic electrochemical reactor configurations such as batch, batch recirculation and continuous recycle reactors, in removing the organic part of wastewater from a medium-scale, specialty chemical industry. The effects of current density, supporting electrolyte concentration, electrolysis duration and fluid flow rate on the pollutant removal and energy consumption performances were critically evaluated. Continuous recycle reactor is found to be the better configuration, because of its flexibility of operation. Circulation flow rate and withdrawal flow rate enable control on transfer coefficients and treatment duration respectively. The ability of artificial neural network (ANN) in predicting the performance of the batch electrochemical treatment has also been demonstrated.

Kinetic studies on sorption of basic dye using Eichhornia crassipes

Sorption capacity of different parts of Eichhornia crassipes, such as rhizome, root, lamina and petiole on basic aurophine-o was studied in a batch system. The equilibrium uptake capacity was observed as 13.65 mg/g (using root), 13.5 mg/g (using lamina), 12.9 mg/g (using rhizome) and 12.75 mg/g (using petiole). It was observed that the equilibrium dye uptake capacity using root was found to be more when compared to all other E. crassipes parts used in the present investigation. The shortcut equations developed are accurate and can be used in the place of experimental data. The shortcut equations form the basis for further research. The intra particle diffusion coefficient (K(i)) and effective diffusion coefficient (D(i)) were evaluated for the removal of dye using root, which were found to be more when compared to all other parts of E. crassipes studied such as, lamina, rhizome and petiole.

Accumulation of Acid Orange 7, Acid Red 18 and Reactive Black 5 by growing Schizophyllum commune

The effect of Acid Orange 7, Acid Red 18 and Reactive Black 5 on the growth and decolorization properties of Schizophyllum commune was studied with respect to the initial pH varying from 1 to 6 and initial dye concentration (10-100 mg/L). The optimum pH value was found to be 2 for both growth and color removal of these azo dyes. Increasing the concentration of azo dyes inhibited the growth of S. commune. It was observed that S. commune was capable of removing Acid Orange 7, Acid Red 18 and Reactive Black 5 with a maximum specific uptake capacity of 44.23, 127.53 and 180.17 (mg/g) respectively for an initial concentration of 100 mg/L of the dye. Higher decolorization was observed at lower concentrations for all the dyes. Finally it was found that the percentage decolorization was more in the case of Reactive Black 5 dye compared to the other two dyes used in the present investigation.

Preparation of steam activated carbon from rubberwood sawdust (Hevea brasiliensis) and its adsorption kinetics

Activated carbon was produced from a biowaste product, rubberwood sawdust (RWSD) using steam in a high temperature fluidized bed reactor. Experiments were carried out to investigate the influence of various process parameters such as activation time, activation temperature, particle size and fluidising velocity on the quality of the activated carbon. The activated carbon was characterized based on its iodine number, methylene blue number, Brauner Emmet Teller (BET) surface area and surface area obtained using the ethylene glycol mono ethyl ether (EGME) retention method. The best quality activated carbon was obtained at an activation time and temperature of 1h and 750 degrees C for an average particle size of 0.46 mm. The adsorption kinetics shows that pseudo-second-order rate fitted the adsorption kinetics better than pseudo-first-order rate equation. The adsorption capacity of carbon produced from RWSD was found to be 1250 mg g(-1) for the Bismark Brown dye. The rate constant and diffusion coefficient for intraparticle transport were determined for steam activated carbon. The characteristic of the prepared activated carbon was found comparable to the commercial activated carbon.

Kinetic and isotherm studies of Cu(II) adsorption onto H3PO4-activated rubber wood sawdust

Adsorption of Cu(II) from aqueous solution onto H(3)PO(4)-activated carbon using rubber wood sawdust (RSAC) was investigated in a batch system. Kinetic and isotherm studies were carried out by considering the effects of various parameters, such as initial concentration, contact time, pH, and temperature. The optimal pH value for Cu(II) adsorption onto RSAC was found to be 6.0. Thermodynamic parameters such as standard Gibbs free energy (DeltaG(0)), standard enthalpy (DeltaH(0)), and standard entropy (DeltaS(0)) were evaluated by applying the Van't Hoff equation. The thermodynamics of Cu(II) adsorption onto RSAC indicates its spontaneous and exothermic nature. Langmuir, Freundlich, and Temkin isotherms were used to analyze the equilibrium data at different temperatures. The Langmuir isotherm fits the experimental data significantly better than the other isotherms. Adsorption kinetics data were tested using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. Kinetic studies showed that the adsorption followed a pseudo-second-order reaction. The initial sorption rate, pseudo-first-order, pseudo-second-order, and intraparticle diffusion rate constants for different initial concentrations were evaluated and discussed. Adsorption mechanism studies revealed that the process was complex and followed both surface adsorption and particle diffusion. The rate-controlling parameter and effective diffusion coefficient were determined using the Reichenberg plot. It was found that the adsorption occurs through film diffusion at low concentrations and at higher concentration the particle diffusion becomes the rate-determining step.

Adsorption of Bismark Brown dye on activated carbons prepared from rubberwood sawdust (Hevea brasiliensis) using different activation methods

Hevea brasiliensis or rubberwood tree, as it is commonly known finds limited use once the latex has been tapped. The sawdust of this tree is chosen to ascertain it viability as a precursor for activation. The carbons thus obtained were characterized in terms of iodine, methylene blue number and surface area. The best carbon in each method was utilized to study the adsorption of Bismark Brown, a dye used in the leather industry. Adsorption equilibrium studies were carried out with the synthetic solutions of the dye, at room temperature (298 K). Equilibrium data are fitted with the Langmuir and the Freundlich isotherms models for the system. The effects of contact time, adsorbent dosage and initial dye concentrations on sorption capacity were carried out. Excellent adsorption capacities of 2000 and 1111 mg g(-1) were obtained for steam and chemical followed by steam-activated carbons, respectively. Pilot-plant experimental studies have been performed using packed-bed column with different feed concentrations, flow rates and bed heights, to evaluate sorption of Bismark Brown on steam-activated carbon. Bed depth service time (BDST) design model have been used to analyze the data.

Chromium(VI) adsorption from aqueous solution by Hevea Brasilinesis sawdust activated carbon

Adsorption capacity of Cr(VI) onto Hevea Brasilinesis (Rubber wood) sawdust activated carbon was investigated in a batch system by considering the effects of various parameters like contact time, initial concentration, pH and temperature. Cr(VI) removal is pH dependent and found to be maximum at pH 2.0. Increases in adsorption capacity with increase in temperature indicate that the adsorption reaction is endothermic. Based on this study, the thermodynamic parameters like standard Gibb's free energy (DeltaG degrees ), standard enthalpy (DeltaH degrees ) and standard entropy (DeltaS degrees ) were evaluated. Adsorption kinetics of Cr(VI) ions onto rubber wood sawdust activated carbon were analyzed by pseudo first-order and pseudo second-order models. Pseudo second-order model was found to explain the kinetics of Cr(VI) adsorption most effectively. Intraparticle diffusion studies at different temperatures show that the mechanism of adsorption is mainly dependent on diffusion. The rate of intraparticle diffusion, film diffusion coefficient and pore diffusion coefficient at various temperatures were evaluated. The Langmuir, Freundlich and Temkin isotherm were used to describe the adsorption equilibrium studies of rubber wood sawdust activated carbon at different temperatures. Langmuir isotherm shows better fit than Freundlich and Temkin isotherm in the temperature range studied. The result shows that the rubber wood sawdust activated carbon can be efficiently used for the treatment of wastewaters containing chromium as a low cost alternative compared to commercial activated carbon and other adsorbents reported.

Pichia humboldtii sp. nov., the perfect state of Candida ingens

The perfect state of Candida ingens was found after treatment with N-methyl-N'-nitro-N-nitrosoguanidine, a mutagenic agent. The species fits into the genus Pichia. A description of Pichia humboldtii is given.