Removal of Congo Red dye from Wastewater Using Orange Peel as an Adsorbent

Present study deals with the utilization of orange peel as an adsorbent for the removal of Congo Red (CR) dye from aqueous solution. The proximate analysis revealed that, the adsorbent has porous structure with volatile matter of about 79.14% and fixed carbon 13.08%. The adsorbent has neutral charge at the pH of 6.37. From the batch adsorption study, the optimum adsorbent dose found 40 g/L, the optimum pH was found to be 6.43 and equilibrium time was found 3 h. The increase in adsorption with temperature shows the endothermic nature of adsorption process. The maximum percent removal of CR was found to be 94.24 at the initial concentration of 100 mg/L at 30 °C. The isotherm analysis shows that the Langmuir adsorption isotherm is best-fitted for Congo Red adsorption on orange peel followed by Freundlich and Temkin isotherm equations. The values of the constants KL and qm are 0.053 L/mg and 11.919 mg/g respectively. Thermodynamic study shows the endothermic nature nature of the adsorption process. The heat of adsorption (∆H) was found to be 21.475 KJ/mol and change in entropy (∆S) was found 0.149 KJ/mol K. Gibbs free energy (∆G) was found -24.633, -26.548 and -28.464 kJ/mol. The adsorption process is found to be feasible and spontaneous. The orange peel can be utilized as an adsorbent for the removal of other pollutants

Removal of crystal violet and methylene blue dyes using Acacia Nilotica sawdust activated carbon

52-68Removal of crystal violet dye (CV) and methylene blue dye (MB) from aqueous solution using activated carbon prepared from Acacia Nilotica sawdust (ACS) has been reported. The physico-chemical properties of ACS such as surface morphology, surface area, pore volume and composition are determined by proximate, BET, SEM and FTIR analyses. Batch experiments are performed to see the effect of different parameters like adsorbent dose, pH, contact time, initial dye concentration and temperature for CV and MB removal. The kinetic studies are carried out using pseudo first and second order kinetic models. To examine the nature of adsorption, to find and optimize the best-fit isotherm, Langmuir, Freundlich, Redlich-Peterson and Radke-Prausnitz isotherm equations along with ARE, MPSD and HYBRID error functions are used. The adsorption of CV and MB dyes onto ACS follows Redlich-Peterson isotherm and second order kinetic model. The maximum removal CV and MB is found to be 99.64% and 99.96% for the concentration of 50 mg/L and 41.71% and 95.14% for the concentration of 500 mg/L, respectively. The optimum adsorbent dosage for CV and MB are found to be 8 g/L and 10 g/L respectively with 1 h contact time at 303 K temperature. The thermodynamic effect of CV and MB onto ACS show the endothermic nature of sorption

Adsorption of an emerging contaminant (primidone) onto activated carbon: kinetic, equilibrium, thermodynamic, and optimization studies

The current study addresses the removal of an emerging environmental contaminant (primidone) in batch adsorption experiments using commercial-grade powdered activated charcoal (PAC). The experiments for the removal of primidone were performed to identify the effect of various adsorption parameters. The secondorder rate expression best represented the adsorption kinetics data. The Freundlich isotherm equation was best fitted to the experimental adsorption data at equilibriumfor removal of primidone using PAC. The values for change in entropy (ΔSo) were positive, which indicates that the degree of freedomof the process increases. The negative values of change in enthalpy (ΔHo) and change in Gibb’s free energy (ΔGo) indicate that the physical adsorption is a dominant phenomenon, and the process is feasible and spontaneous. The negative value of ΔHo also represented the exothermicity of the adsorption process. The Taguchi optimization technique calculated the influence of variation of different process parameters, viz., initial pH (pH0), PAC dosage (m), initial adsorbate concentration (C0), solution temperature (T), and process contact time (t), on the removal of primidone by adsorption from aqueous solution. Each of the above parameters was examined at three levels to study their effects on the adsorptive uptake of primidone using PAC (qe, mg g−1), and the optimum value necessary to maximize qe was determined. The findings from the ANOVA indicate that the PAC dose (m) is the most notable parameter contributing 62.16% to qe and a 71.96% to the signal to noise (S/N) ratio data, respectively. The confirmation experiments performed at the optimum parameter condition validated the applicability of the Taguchi design of experiments. The percent removal and adsorptive uptake at the optimal condition were 86.11% and 0.258 mg g−1, respectively

Optimization of fluoride removal using ultrasonically improved electrochemically generated adsorbent: A Taguchi approach

Ultrasonically improved electrochemically generated adsorbent (UEGA) has been synthesized and used for adsorption of fluoride ions from fluoride laden waste water. UEGA was prepared in two major steps, firstly electrochemically generated adsorbent (EGA) was prepared using electrolytic method followed by ultrasonication treatment. Ultrasonication causes size reduction which leads to increase in surface area viz. active site which helps to enhance attachment of negatively charged fluoride ion on positively changed UEGA from waste water. UEGA was prepared at three different amplitude i.e. 50, 70 and 90% respectively. Taguchi optimization for defluoridation was carried out considering operating parameters such as initial concentration; contact time; adsorbent dose; and temperature. The results obtained demonstrated that adsorption showed different fluoride removal at varying frequency. This study proved that varying percentage amplitude of ultrasonication significantly affects defluoridation efficiency

Preparation and Characterization of Polyalthia longifolia Based Alumina as a Novel Adsorbent for Removing Fluoride from Drinking Water

This research addresses i) synthesis of an alumina composite based on high capacity adsorbent using a leaf as a template and ii) the issue of handling spent regenerant resulting from regeneration of such high capacity adsorbents. A low-cost composite type adsorbent has been synthesized for removal of excess fluoride from drinking water, using Polyalthia longifolia (false Ashoka tree) leaf as a template and alum as a source of alumina. The composite adsorbent having heterogeneous phases of Al(OH)3 and Al2O3 is associated with carbon and free Al(OH)3 and alumina has been identified using XRD, SEM, FTIR and BET surface area analysis. Batch adsorption experiments were carried out including the effect of various physico-chemical parameters, such as adsorbent dose, pH, contact time, initial fluoride ion concentration and temperature to ascertain optimal performance conditions. The elemental composition of material and SEM analysis suggests a composite material with different phases. Polyalthia longifolia based adsorbent (PBA) effectively removes fluoride with substantially high adsorption capacity of 17.57 mg g-1 at initial fluoride concentration of 5 mg l-1 using very low dose of 0.4 g l-1 as compared to 1.82 mg g-1 for activated alumina. PBA has been regenerated to the tune of about 80% using alum solution. The spent regenerant has been subjected to two new options i) recovery of alum and formation of chitosan/CaF composite by treating with slaked lime and ii) immobilization of AlF in chitosan to form chitosan/AlF composite. These composites may prove to be useful optic materials for UV absorption

An Alternative to Clay in Building Materials: Red Mud Sintering Using Fly Ash via Taguchi’s Methodology

“Red mud” or “bauxite residue” is a highly alkaline waste generated from alumina refinery with a pH of 10.5–12.5 which poses serious environmental problems. Neutralization or its treatment by sintering in presence of additives is one of the methods for overcoming the caustic problem as it fixes nearly all the leachable free caustic soda present in red mud. In the present study, feasibility of reducing the alkaline nature of red mud by sintering using fly ash as an additive via Taguchi methodology and its use for brick production, as an alternative to clay, is investigated. The analysis of variance (ANOVA) shows that sintering temperature is the most significant parameter in the process. A pH of 8.9 was obtained at 25–50% of red mud and 50–75% fly ash with water and temperature of . Alternatively 50% of red mud can be mixed with 50% of fly ash with water at temperature of to get a pH of about 8.4. The mechanism of this process has been explained with also emphasis on chemical, mineralogical, and morphological analysis of the sintered red mud. The results would be extremely useful in utilization of red mud in building and construction industry.by Jyoti Mukhopadhyay et al.

An Alternative to Clay in Building Materials: Red Mud Sintering Using Fly Ash via Taguchi’s Methodology

“Red mud” or “bauxite residue” is a highly alkaline waste generated from alumina refinery with a pH of 10.5–12.5 which poses serious environmental problems. Neutralization or its treatment by sintering in presence of additives is one of the methods for overcoming the caustic problem as it fixes nearly all the leachable free caustic soda present in red mud. In the present study, feasibility of reducing the alkaline nature of red mud by sintering using fly ash as an additive via Taguchi methodology and its use for brick production, as an alternative to clay, is investigated. The analysis of variance (ANOVA) shows that sintering temperature is the most significant parameter in the process. A pH of 8.9 was obtained at 25–50% of red mud and 50–75% fly ash with water and temperature of . Alternatively 50% of red mud can be mixed with 50% of fly ash with water at temperature of to get a pH of about 8.4. The mechanism of this process has been explained with also emphasis on chemical, mineralogical, and morphological analysis of the sintered red mud. The results would be extremely useful in utilization of red mud in building and construction industry