Mithilesh Kumar Jha

Application of Central Composite Design approach for removal of chromium (VI) from aqueous solution using weakly anionic resin: Modeling, optimization, and study of interactive variables

In this paper, response surface methodology (RSM) approach using Central Composite Design (CCD) is applied to develop mathematical model and optimize process parameters for Cr (VI) removal from aqueous streams using weakly anionic resin Amberlite IRA 96. The individual and combined effect of four process parameters, i.e. contact time, initial solution pH, initial Cr (VI) concentration and resin dose on Cr adsorption were studied. Analysis of variance (ANOVA) showed the relative significance of process parameters in removal process. Initial solution pH and resin dose were found to be more significant than contact time and initial Cr (VI) concentration. The second-order regression model was developed to predict the removal efficiency using Design Expert software. The optimal conditions to remove Cr from aqueous solution at constant temperature of 30°C and stirring speed of 250 rpm were found to be contact time 62.5 min, pH 1.96, initial Cr (VI) concentration 145.4 mg/L, and resin dose 8.51 g/L. At these conditions, high removal efficiency (93.26%) was achieved. FTIR and EDX analysis were conducted to interpret the functional groups involved during the Cr-resin interaction.

An integrated approach to remove Cr(VI) using immobilized Chlorella minutissima grown in nutrient rich sewage wastewater.

The potential of an integrated system for sewage wastewater treatment and biosorption of chromium(VI) was evaluated using immobilized Chlorella minutissima cells. Immobilized algal cells were grown in sewage wastewater in designed photobioreactor for 48 h and then subjected to removal of Cr(VI) from synthetic wastewater. The effect of pH, Cr(VI) concentration, biosorbent dose on Cr(VI) removal was investigated. C. minutissima showed a higher NH(4)(+)-N and PO(4)(3-)-P removal efficiency (above 99% removal) than the NO(3)(2-)-N (58% removal) in 48 h. Biosorption of Cr(VI) was found to be highly dependent on solution pH, biosorbent dose and initial Cr(VI) concentration. Maximum Cr(VI) uptake 57.33 mg Cr(VI)/g dry biosorbent/L of solution was observed at pH2 with 20% (w/v) biosorbent. Further more than 90% of total Cr adsorbed could be recovered using 0.5 M NaOH as desorption medium.

Pyrolysis kinetics and thermodynamic parameters of castor (Ricinus communis) residue using thermogravimetric analysis

Castor plant is a fast-growing, perennial shrub from Euphorbiaceae family. More than 50% of the residue is generated from its stems and leaves. The main aim of this work is to study the pyrolytic characteristics, kinetics and thermodynamic properties of castor residue. The TGA experiments were carried out from room temperature to 900 °C under an inert atmosphere at different heating rates of 5, 10, 15, 20, 30 and 40 °C/min. The kinetic analysis was carried using different models namely Kissinger, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The average Eɑ calculated by FWO and KAS methods were 167.10 and 165.86 kJ/mole respectively. Gibbs free energy varied from 150.62-154.33 to 150.59-154.65 kJ/mol for FWO and KAS respectively. The HHV of castor residue was 14.43 MJ/kg, considered as potential feedstock for bio-energy production. Kinetic and thermodynamic results will be useful input for the design of pyrolytic process using castor residue as feedstock.

Catalytic Hydrothermal Liquefaction of Waste Furniture Sawdust to Bio-oil

Abstract The objective of present study is to investigate the effect of alkalis (NaOH, Na2CO3, KOH and K2CO3) on hydrothermal liquefaction of waste furniture sawdust (mixture of different types of waste woods) under sub-critical water conditions in a batch reactor operating at 280°C for 15 min. The liquefaction products were analysed using Fourier transform infrared spectroscopy, elemental composition, higher heating value and gas chromatography-mass spectrometry (GC-MS). The highest total bio-oil yield (34.9 wt%) and lowest solid residue yield (6.8 wt%) was obtained in the presence of 1.0 M K2CO3. Reactivity order for alkalis based on biomass conversion and liquid yield was found to be K2CO3 > KOH > Na2CO3 > NaOH. The experimental results showed that the bio-oils produced were enriched in carbon and hydrogen and had reduced level of oxygen compared with original sawdust. The GC-MS analysis showed that light bio-oils and heavy bio-oils comprised a complex mixture of organic compounds, which mainly include phenols and their derivatives.

Characterization, activity and process optimization with a biomass-based thermal power plant's fly ash as a potential catalyst for biodiesel production

A typical thermal power plant operated using a solid biomass mixture as fuel, which comprised 70–80% gram straw, 10–15% cotton straw, 5–10% wheat straw and leaves (2%) with a small quantity of coal (1–2%) initially used for smooth ignition, produces a residue called Biomass-Based Thermal Power Plant Fly Ash (BBTPFS). BBTPFS was investigated for composition and structural characterization using different techniques. The versatile composition of the BBTPFS was confirmed by XRF analysis that indicated the weight percent of different components viz. CaO (30.74%), SiO2 (27.87%), K2O (13.96%), MgO (6.67%), SO3 (4.83%), Cl (3.36%), Al2O3 (2.83%), Fe2O3 (2.36%), P2O5 (1.34%), Na2O (1.14%), small quantities of TiO2, SrO, MnO, BaO, ZrO2, ZnO, Rb2O, Br, Cr2O3, CuO, NiO and As2O3 as active ingredients. The SEM and TEM image analysis showed the surface morphology of the BBTPFS which was found to be mixed in nature, having 1 to 500 nm range particles with meso, micro and macro porosity. BBTPFS was used as a catalyst for transesterification of Jatropha curcas oil having a high percentage of free fatty acids and appropriate process optimization was achieved using the Taguchi-ANOVA method. It was observed that at a temperature of 225 °C and an internal vapour pressure of 3.2 MPa in a batch reactor with 5% catalyst loading, 1:9 mol mol−1 of oil–alcohol and 3 h reaction time, the optimum yield of biodiesel obtained was ∼93.9%, which is in agreement with the theoretical value. The product quality was assessed and found to conform to ASTM and EN-standards.

Sulfide oxidation in fluidized bed bioreactor using nylon support material

A continuous fluidized bed bioreactor (FBBR) with nylon support particles was used to treat synthetic sulfide wastewater at different hydraulic retention time of 25, 50 and 75 min and upflow velocity of 14, 17 and 20 m/hr. The effects of upflow velocity, hydraulic retention time and reactor operation time on sulfide oxidation rate were studied using statistical model. Mixed culture obtained from the activated sludge, taken from tannery effluent treatment plant, was used as a source for microorganisms. The diameter and density of the nylon particles were 2-3 mm and 1140 kg/m3, respectively. Experiments were carried out in the reactor at a temperature of (30 +/- 2) degrees C, at a fixed bed height of 16 cm after the formation of biofilm on the surface of support particles. Biofilm thickness reached (42 +/- 3) microm after 15 days from reactor start-up. The sulfide oxidation, sulfate and sulfur formation is examined at all hydraulic retention times and upflow velocities. The results indicated that almost 90%-92% sulfide oxidation was achieved at all hydraulic retention times. Statistical model could explain 94% of the variability and analysis of variance showed that upflow velocity and hydraulic retention time slightly affected the sulfide oxidation rate. The highest sulfide oxidation of 92% with 70% sulfur was obtained at hydraulic retention time of 75 min and upflow velocity of 14 m/hr.

Effect of process parameters on hydrothermal liquefaction of waste furniture sawdust for bio-oil production

In the present study, hydrothermal liquefaction of waste furniture sawdust was examined. The effects of various reaction conditions such as reaction temperature (180–300 °C), residence time (0–60 min), water to sawdust ratio (2–10) and initial N2 pressure (0–2 MPa) on the product yields were studied using a high pressure batch reactor in order to determine the optimal liquefaction parameters for the production of maximum bio-oil yield. The solid residue was characterized to investigate the mechanism of hydrothermal liquefaction process by FT-IR. The highest sawdust conversion (61.6 wt%) and bio-oil yield (12.7 wt%) were obtained at 280 °C, 15 min and ratio of the water to sawdust of 6 with initial N2 pressure of 1.0 MPa. The higher heating values (HHVs) of the bio-oils were found to be within the range of 17–30 MJ kg−1. The GC-MS analysis revealed that sawdust liquefaction bio-oils comprised a complex mixture of organic compounds, which include alcohols, acids, aldehydes, ketones, esters, phenols and their derivatives.

Hydrothermal liquefaction of wood: a critical review

Abstract This article provides an overview of previous research contributions and the current status of technology on the hydrothermal liquefaction (HTL) of wood biomass into liquid fuels and valuable chemicals. This process involves the direct liquefaction of biomass, which operates from 200°C to 400°C, 5 to 25 MPa, and 10 to 60 min reaction time in hot-compressed water or solvent and with or without a catalyst in the presence of inert or reducing gas. The influence of process variables, including biomass composition, temperature, residence time, pressure, heating rate, particle size, catalysts, and so on, which are significant for the bio-oil yield and product quality, has been addressed in this review. This review focuses on the HTL fundamentals based on current knowledge and summarizes the state-of-the-art knowledge of the HTL of wood biomass.

Comparative Studies on Uptake of Wastewater Nutrients by Immobilized Cells of Chlorella minutissima and Dairy Waste Isolated Algae

Abstract The present study has been carried out to assess the nutrient removal potential of two different algal species in immobilized alginate beads for nutrient removal from wastewater. Chlorella minutissima and wild algae isolated from a local dairy waste treatment plant were used in the study. The percentage removal of nutrients (ammonia-N, phosphate and nitrate-N) by algal alginate beads at different time intervals in an aerated photobioreactor has been investigated. Percentage removal of ammonia-N (94% in 48 h) was higher for C. minutissima while dairy waste isolated algae species showed significant removal efficiency for phosphate (100% in 48 h) and nitrate-N (62.5% in 48 h). The study showed that immobilized Chlorella minutissima and isolated wild algae beads were significantly efficient in removing ammonia-N and phosphate from local sewage wastewater.

Transesterification of Prunus armeniaca oil using calcium methoxide as a catalyst: Identification of methyl esters and proposed mechanistic pathways

ABSTRACT The utilization of nonedible feedstocks for biodiesel production is getting top priority in the recent years, as they do not interfere with the global food economy. In the present study, calcium methoxide (Ca(OCH3)2) catalyst was synthesized for the production of biodiesel from Prunus armeniaca oil via transesterification reaction. Under optimized reaction conditions, the biodiesel yield of 89.93% was achieved and catalyst could be reused for four times with slight loss in activity. The fatty acid methyl esters in the produced biodiesel were detected by gas chromatography/mass spectrometry (GC/MS), and six fragments were identified based on mass-to-charge ratio (m/z) at different retention time. The fuel properties of the biodiesel obtained were in conformity with the ASTM standards.