• Energy Research

This study was aimed to assess the adsorption capacity of residual black toner ink (RBTI) for the removal of heavy metal Cr (VI), ions in batch mode. To achieve this objective, the effects of different experimental parameters viz., initial Cr (VI) concentration, adsorbent dose, initial pH of solution and temperature on Cr (VI) uptake were studied. The kinetic parameters were evaluated using model equations of Lagergren (pseudo first order), pseudo second order, and Weber and Morris. The Langmuir, Freundlich, Dubinin–Radushkevich isotherms were fitted to experimental data for establishing the adsorption equilibrium. Calculation of thermodynamic parameters (ΔGº, ΔHº, ΔSº) was also done to demonstrate the nature of adsorption. Thermodynamic parameters (ΔGº= −2.5885 kJ/mol, ΔHº= 282.74 kJ/mol, ΔSº= 0.9574 kJ/mol.K) revealed that adsorption of Cr (VI) using RBTI was endothermic, spontaneous and increased with temperature. To investigate the physical and chemical properties of RBTI, SEM‐EDX and FTIR analyses were done. The maximum adsorption capacity of RBTI for Cr (VI) removal was found to be 13.98 mg/g. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1022–1029, 2017

Torrefaction has been proven as a promising pretreatment process that can effectively reduce the moisture content and increase the energy density and higher heating value (HHV) of raw biomass and c...

Abstract Pyrolysis is important method to harness bio-energy from not easily degradable biomass to meet today's energy requirement. The fixed bed slow pyrolysis of walnut shell was performed in continuous inert atmosphere to find out the effect of process parameters like temperatures (300–600 °C), particle size (0.25–1.00 mm), and bed height (8–12 cm) on yield and product characteristics. Walnut shell was pretreated with phosphoric acid at different concentrations (0.2–0.8 M) to improve yield and properties of pyrolysis products by removing inorganics and solubilizing lignin-hemicellulose components of biomass. Pretreatment showed enhanced biochar and bio-oil yield. Characterization of biochar was done using proximate, ultimate analyses, FTIR, XRD, SEM-EDX, etc. The physicochemical properties of liquid product such as viscosity, density, carbon residue, HHV and FTIR were determined. Pyrolytic gas composition was analyzed using GC-TCD and GC-FID. The properties of biochar inferred its utility as solid fuel or in waste water treatment as it has high BET surface area. The properties of bio-oil disclose its utility as blend fuel or a source of different valuable chemicals. Presence of CH4, H2 and CO in pyrolytic gas recommends good combustion behaviour. Thus above results describe the bio-energy potential of walnut shell.

Abstract Biogas utilization in fuel cell technology and hydrogen generation is a modern and economically viable approach. A pretreatment step prior to anaerobic digestion (AD) is obligatory to increase the hydrolysis, solubilize the complex matter present in organic fraction of municipal solid waste (OFMSW) and to achieve higher yield of biogas. This study was intended to find out the effects of thermal, chemical and thermochemical pretreatments on the properties and structure of OFMSW and also on biogas production. There was an increase in chemical oxygen demand of 6.87, 1.61 and 11.60% for thermal, chemical and thermochemical pretreatments, respectively. Also, the content of volatile solids was reduced by 2.36% by thermochemical pretreatment. FTIR, XRD and SEM analysis revealed that these pretreatments also caused chemical and morphological changes on the substrate, as a result reduced its crystallinity and enhanced the rate of hydrolysis. A significant increase of 54% in biogas yield was achieved after thermochemical pretreatment in comparison to untreated OFMSW sample.

The treatment of methyl parathion (MP) aqueous solution with the application of Fenton oxidation using catalyst (Fe2+) was investigated under batch mode of operation. The aims of this study are to evaluate the COD removal and removal efficiency of MP from aqueous solution by Fenton reagent and investigate the role of different parameters such as concentration of initial pH, Fe2+ dosage, H2O2 dosage, initial concentration of MP, temperature, and reaction time. The initial COD value was 440 mg/L for MP concentration of 11.4 × 10−5 M. It was observed that removal was faster at acidic pH and maximum COD and MP removal were 64.54 and 74%, respectively, at pH value 3. When vary the doses of H2O2, maximum COD and MP removal of 79 and 92%, respectively, were achieved at H2O2 concentration of 6.53 × 10−1 M, Fe2+ concentration 8.99 × 10−3 M and pH 3. Regarding degradation kinetics of MP, Behnajady–Modirshahla–Ghanbery model showed high correlation coefficient (R2) as compared with first‐order and second‐order models at different operating conditions using Fenton oxidation. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 420–427, 2017

The research work aims to estimate the bioenergy potential of pistachio shell and study its degradation kinetics which is necessary for the efficient design and optimization of thermochemical processes for bioenergy generation. Initial characterizations (proximate, ultimate, higher heating value, and compositional analysis), kinetic study, and thermodynamic analysis accompanied by reaction mechanism are investigated. Physicochemical characterization results confirmed high volatile matter (~ 79.8 wt%) and high heating value (16.85 MJ/kg) of pistachio shell. Thermogravimetric analysis (TGA) is performed at four different heating rates of 10, 20, 30, and 40 °C/min under nitrogen gas flow rate from ambient temperature to 900 °C. TGA results show the three-stage pyrolysis reaction which involves removal of moisture and light volatiles, degradation of cellulose and hemicellulose, and decomposition of lignin. The result also reveals that maximum degradation occurred in the temperature range of 200–400 °C. For calculating the kinetic (activation energy and pre-exponential factor) and thermodynamic parameters (enthalpy, entropy, and Gibbs free energy), different iso-conversional models, i.e. Flynn-wall-Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink, and Friedman, are employed which gives the average value of activation energy as 168.86, 165.80, 166.29, and 190.10 kJ/mol, respectively and the pre-exponential factor values lie in the range of 107-1021 s−1. The average values of Gibbs free energy calculated for FWO, KAS, Starink, and Friedman methods are 182.09, 182.15, 182.13, and 181.42 kJ/mol, respectively. Criado method and Z plot are showing complex reaction mechanism. The results of kinetics and thermodynamic study reveal pistachio shell is an efficient biomass for bioenergy production.

Excessive phosphate effluent discharged in the surface water source rush to eutrophication. Consecutively this disturbs the water quality and aquatic ecosystem, due to the depletion of dissolved oxygen. Reduced oxygen level in water bodies affects aquatic life and decreases biodiversity. The present investigation emphasized the phosphate adsorption over nano‐alumina. Surface characteristics of the adsorbents, BET, FTIR, XRD, TEM, and SEM were analyzed to reveal the phosphate adsorption mechanisms. The adsorption isotherms, kinetics, pH effect were observed in batch experiments. The pHpzc value of nano‐alumina adsorbent was found as 8.1. The maximum phosphate adsorption was found to be 98.75% at contact time of 90 min and pH 6. Different models, e.g., Langmuir, Freundlich, Temkin, and Dubinin‐Radushkevich were used for isotherm study. The kinetic data were tested by pseudo‐first order and second order models. An attempt was made to regenerate the spent adsorbent for reuse in the adsorption process. Low cost and high capability of nano‐alumina make it feasible to utilize as cost‐effective phosphate remediation from wastewater. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S77–S85, 2019

Abstract The process parameters (temperature, residence time and heating rate) for torrefaction of Acacia nilotica in a fixed-bed reactor were optimized using response surface methodology. Maximum higher heating value and energy yield, both at the same time, were obtained at 252 °C , 60 min residence time, and 5 °C /min heating rate. Both the parameters were highly influenced by temperature; whereas residence time and heating rate had minimal impact. The torrefied biomass obtained at optimum condition was characterized by proximate and ultimate analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. Moisture content, H/C ratio and O/C ratio decreased by 73.23, 52.94, and 46.22%, respectively; while fixed carbon and higher heating value increased by 75.54 and 18.62%, respectively, as compared to raw biomass. Fuel properties such as fuel ratio increased by 87.39%, while combustibility index and volatile ignitability decreased by 83.32 and 22.71%, respectively. Flow properties such as angle of repose, Hausner ratio, Carr compressibility index and cohesion coefficient decreased by 8.04, 6.20, 22.48 and 12.5%, respectively. Enhanced fuel and flow properties make torrefied biomass a suitable feedstock for pyrolysis and gasification and optimization of this process may facilitate scale-up and reduce operational cost.

Abstract Torrefaction of Acacia nilotica was carried out in a quartz fixed-bed reactor. Temperature and residence time varied from 220 to 280 °C and 20–60 min. The fuel (volatile ignitability (VI), combustibility index (CI), fuel ratio (FR)), and flow (Hausner ratio (HR), cohesion coefficient (C), Carr compressibility index (CCI), angle of repose) properties were investigated for raw and torrefied biomass. Torrefied biomass was also characterized through TGA, FTIR, SEM-EDX and ICP-MS analysis. For moisture sorption test, contact angle was measured. Finally, torrefied biomass was compared with coal using published literature. The HHV, fixed carbon content, FR of raw biomass at 280 °C for 40 min was increased from 19.31 to 24.76 MJ/kg, 11.35 to 60.40 wt %, and 0.13 to 1.63, respectively. While, VI, CI, C, CCI and bulk density of raw biomass at similar condition of torrefaction decreased from 15.76 to 15.37 (MJ/kg), 147.40 to 17.37 (MJ/kg), 0.40 to 0.33, 22.85 to 15.86 and 230.82 to 172.84 (kg/m3), respectively. ICP-MS analysis revealed that torrefied biomass was enriched in sodium, potassium, calcium, magnesium, etc. At similar torrefaction condition, the moisture absorbed by raw and torrefied biomass was 35.44% and 6.61%, respectively. Contact angle (79.1°/77.5°) for torrefied biomass suggested its hydrophobic nature.

Biogas production from organic fraction of municipal solid waste (OFMSW) not only helps in solid waste management but also combat the food vs fuel dilemma. The presence of lignocellulosic material and other complex compounds in OFMSW hinder biogas production. Therefore, pretreatment is an essential step to increase the hydrolysis rate by converting complex compounds to simpler ones. This work was aimed at effective pretreatment of OFMSW by biological and thermo-chemical means. For biological pretreatment lignin degrading fungal strains, Phanerochaete chrysosporium and Pleurotus ostreatus were employed. Thermo-chemical treatment resulted in higher solubilisation yield in terms of sCOD and VFA making it a more effective method as compared with biological pretreatment. The optimisation of thermo-chemical pretreatment was done by the Box-Behnken design of response surface methodology (RSM). The interactive effect of influencing factors NaOH dose, temperature and time were studied on the response of sCOD, VFA and phenolic content. The sCOD and VFA values were significantly increased by increasing the NaOH concentration, temperature and time to a certain limit. The optimised condition from RSM for maximum solubilisation yield in terms of sCOD, VFA and phenolic content was found to be NaOH dose of 4.72 g/L, temperature 180 °C and time 30.3 min. Biogas production was increased by 169.5% after pretreatment at RSM optimised conditions as compared with untreated OFMSW.