Chromium metal is found in industrial wastewater at a much higher concentration than the prescribed limit set by different regulatory authorities. Since chromium(VI) is very toxic and carcinogenic, it requires removal at source, that is, before its discharge to the water bodies. The present study is carried out for removal of Cr(VI) from aqueous solution by using locally available rubber leaf as a low-cost adsorbent in batch and continuous column mode. The effects of pH, adsorbent dose, contact time, initial metal ion concentration, and temperature on removal of Cr(VI) were studied in batch process. Different kinetic and isotherm models were examined and the model parameters were determined. The column studies were conducted to investigate the effects of flow rate, bed height, and initial metal ion concentration on removal efficiencies. The experimental data reflects reasonably with Thomas and Yoon–Nelson models in continuous mode. © 2015 Balaban Desalination Publications. All rights reserved.

SUDIP DAS

Chemical Engineering

S NAG

A MONDAL

U MISHRA

N BAR

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Removal of chromium(VI) from aqueous solutions using rubber leaf powder: batch and column studies

Desalination and Water Treatment

The paper aims to provide efficient and affordable means for pollution abatement to MSME sector. In this work, the performance of some naturally available bio-waste materials, viz., leaves of jackfruit, mango and rubber plants have been attempted as biosorbents for remediation of toxic Cd(II) from aqueous solution. The biomasses have been characterized to find out the surface morphology, active surface area, presence of characteristic surface groups etc. which facilitate the biosorption process. Batch experiments are conducted to see the effects of operating parameters, viz., aqueous phase pH, initial Cd(II) concentration, adsorbent dose, time, temperature for Cd(II) ion removal onto these green biomaterials. The bioremediation mechanism was strongly pH dependent, spontaneous and followed second-order kinetics. Mass transfer, intra-particle diffusion and chemical adsorption controlled the process. Jackfruit leaf showed the best sorption performance by removing 98.72% Cd(II) from 20 mg L−1 aqueous solution at a dose of 5 g L−1 and the equilibrium adsorption capacity of 20.37 mg g−1. The bio-sorbents performed satisfactory when tested against the industrial wastewater. The toxicity effect of the cadmium ion was analysed on living animal cell and they showed morphological alteration of RBC along with clumped appearance. The cell alteration intensity reduced with the treated effluent. The natural adsorbents have comparable adsorption capacity of other green adsorbents used by different researchers. Modelling of the complex sorption process has been performed using hybrid artificial intelligence (GA-ANN) technique to predict the metal ion removal efficiency accurately and obtained results have good agreement with the experimental data with correlation coefficient (R) ranging from 0.97–0.99. All these findings have manifested application of jackfruit, rubber and mango leaves for removal of Cd(II) ions in an environmentally sustainable and friendly way. © 2018 Elsevier B.V.

Environmental Technology and Innovation

Sustainable bioremediation of Cd(II) from aqueous solution using natural waste materials: Kinetics, equilibrium, thermodynamics, toxicity studies and GA-ANN hybrid modelling

Cr(VI) is a toxic water pollutant, which causes cancer and mutation in living organisms. Adsorption has become the most preferred method for removal of Cr(VI) due to its high efficiency and low cost. Peanut and almond shells were used as adsorbents in downflow fixed bed continuous column operation for Cr(VI) removal. The experiments were carried out to scrutinise the adsorptive capacity of the peanut shells and almond shells, as well as to find out the effect of various operating parameters such as column bed depth (5–10 cm), influent flow rate (10–22 ml min−1) and influent Cr(VI) concentration (10–20 mg L−1) on the Cr(VI) removal. The fixed bed column operation for Cr(VI) adsorption the equilibrium was illustrated by Langmuir isotherm. Different well-known mathematical models were applied to the experimental data to identify the best-fitted model to explain the bed dynamics. Prediction of the bed dynamics by Yan et al. model was found to be satisfactory. Applicability of artificial neural network (ANN) modelling is also reported. An ANN modelling of multilayer perceptron with gradient descent and Levenberg-Marquardt algorithms have also been tried to predict the percentage removal of Cr(VI). This study indicates that these adsorbents have an excellent potential and are useful for water treatment particularly small- and medium-sized industries of third world countries. Almond shell represents better adsorptive capacity as breakthrough time and exhaustion time are longer in comparison to peanut shell. © 2017, Springer-Verlag Berlin Heidelberg.

Environmental Science and Pollution Research

Comparative study of adsorptive removal of Cr(VI) ion from aqueous solution in fixed bed column by peanut shell and almond shell using empirical models and ANN

Hyacinth root was used as a biosorbent for generating adsorption data in fixed-bed glass column. The influence of different operating parameters like inlet Pb(II) ion concentration, liquid flow rate and bed height on the breakthrough curves and the performance of the column was studied. The result showed that the adsorption efficiency increased with increase in bed height and decreased with increase in inlet Pb(II) ion concentration and flow rate. Increasing the flow rate resulted in shorter time for bed saturation. The result showed that as the bed height increased the availability of more number of adsorption sites in the bed increased, hence the throughput volume of the aqueous solution also increased. The adsorption kinetics was analyzed using different models. It was observed that maximum adsorption capacity increased with increase in flow rate and initial Pb(II) ion concentration but decreased with increase in bed height. Applicability of artificial neural network (ANN) modeling for the prediction of Pb(II) ion removal was also reported by using multilayer perceptron with backpropagation, Levenberg-Marquardt and scaled conjugate algorithms and four different transfer functions in a hidden layer and a linear output transfer function. © 2014 Elsevier B.V.

Journal of Hazardous Materials

Removal of Pb(II) ions from aqueous solution using water hyacinth root by fixed-bed column and ANN modeling

The potentiality of low cost natural/agricultural waste biomasses for the removal of Cu(II) ion from aqueous solution has been investigated in batch experiments. The effect of various physico-chemical parameters such as initial pH, initial Cu(II) concentration, adsorbent dosage, contact time and temperature has been studied. The optimum pH for adsorption was found to be 6 for all adsorbents used. Kinetics data were best described by the pseudo-2nd-order model. The experimental data were fitted well with Freundlich and Halsey isotherm models. The diffusion coefficient and sorption energy indicated that the adsorption process was chemical in nature. Thermodynamic parameters such as Δ G°, Δ H° and Δ S° were calculated, and it was observed that the adsorption process was spontaneous and endothermic. The mean sorption energy was calculated using Dubinin-Radushkevich isotherm model and it confirmed that the sorption process was chemical in nature. Different active functional groups were identified by FTIR studies which were responsible for Cu(II) ion adsorption process. Application study using electroplating industrial waste water and regeneration experiment of the adsorbent were also investigated. Design procedure for the batch process was also reported. © 2013 Elsevier B.V.

Colloids and Surfaces B: Biointerfaces

Adsorptive removal of Cu(II) from aqueous solution and industrial effluent using natural/agricultural wastes

Cr(VI) is a major water pollutant from industrial effluent whose concentration is to be reduced within the permissible limit. Present study reports a systematic evaluation of six different natural adsorbents for the removal of Cr(VI) from aqueous solutions in batch process. The adsorption kinetic data were best described by pseudo-second order model. The values of mass transfer coefficient for Cr(VI) adsorption indicated that the velocity of the adsorbate transport from the bulk to the solid phase was quite fast. The effective diffusivity of Cr(VI) removal for all the adsorbents were of the order of 10-10m2/s which suggested chemisorption of the process. The adsorption process was jointly controlled by film diffusion and intraparticle diffusion. Maximum monolayer adsorption capacities onto the natural adsorbents used were comparable to the other natural adsorbents used by other researchers. The thermodynamic studies and sorption energy calculation using Dubinin-Radushkevich isotherm model indicated that the adsorption processes were endothermic and chemical in nature. FT-IR studies were carried out to understand the type of functional groups responsible for Cr(VI) binding process. Desorption study was carried out with different concentration of NaOH solutions. Application study was carried out using electroplating industrial wastewater. © 2011 Elsevier B.V.

Biosorption of Cr(VI) ions from aqueous solutions: Kinetics, equilibrium, thermodynamics and desorption studies

The removal of Cr(VI) from aqueous solution by batch adsorption technique using different low-cost adsorbents was investigated. Adsorbents such as clarified sludge-a steel industry waste material, rice husk ash, activated alumina, fuller's earth, fly ash, saw dust and neem bark were used to determine the adsorption efficiency. The influence of pH, adsorbent type and concentration, initial Cr(VI) concentration and contact time on the selectivity and sensitivity of the removal process were investigated. Adsorption process was found to be highly pH dependent. The optimum pH range for adsorption of Cr(VI) was found to be between 2 and 3. Kinetics studies were performed to understand the mechanistic steps of the adsorption process and the rate kinetics for the adsorption of Cr(VI) was best fitted with the pseudo-2nd-order kinetic model. Langmuir and Freundlich adsorption isotherms were applicable to the adsorption process and their constants were evaluated. The thermodynamic equilibrium constant and the Gibbs free energy were determined for each system. The adsorption capacity (qmax) calculated from Langmuir isotherm and the Gibbs free energy (ΔGo) value obtained for the different adsorbents showed that clarified sludge was the most effective among the selected adsorbents for the removal of Cr(VI) from aqueous solution. The adsorption efficiencies of rice husk ash and activated alumina were also equally comparable with that of clarified sludge. © 2007.

Journal	Data powered by TypesetDesalination and Water Treatment
Publisher	Data powered by TypesetTaylor and Francis Inc.
ISSN	1944-3994