Mechanism of Cr(VI) uptake onto sagwan sawdust derived biochar and statistical optimization via response surface methodo
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ORIGINAL ARTICLE
Mechanism of Cr(VI) uptake onto sagwan sawdust derived biochar and statistical optimization via response surface methodology Goutam Kishore Gupta 1 & Monoj Kumar Mondal 1 Received: 19 August 2020 / Revised: 2 October 2020 / Accepted: 9 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The present study elaborates the use of sagwan sawdust biochar as an efficient adsorbent for Cr(VI) abatement. Effect of experimental variables like solution pH (2–10), initial Cr(VI) concentration (30–100 mg/L), temperature (30–40 °C), adsorbent dose/Cr(VI) concentration (16.67–200), and contact time (10–80 min) was studied through batch operations. The optimization and interaction study for process parameters was done by employing response surface methodology through Box-Behnken design. The optimized condition for the maximum adsorption was pH 2.07, temperature 30.72 °C, and dose/Cr(VI) concentration 160.93. The surface characteristics of the adsorbent were evaluated via pHzpc, FTIR, BET surface area, SEM-EDS, XRD, and XPS analysis. Functional groups like O-H, C-O, C-H, and C=O were responsible for the adsorption process, and change in the oxidation state of Cr was affirmed by XPS survey. The Cr(VI) adsorption was governed by second-order kinetics and the Langmuir isotherm with Q0 of 9.62 mg/g. The thermodynamic study revealed the process to be exothermic and spontaneous. Mass transfer studies confirmed film diffusion to be favorable in the adsorption process. Adsorption occurred via electrostatic and physical attraction, reduction, and complexation. Therefore, the results suggest sagwan sawdust biochar is satisfactory and effective in removing Cr(VI) from aqueous solution. Keywords Adsorption . Biochar . Kinetics . Mass transfer . Mechanism . Optimization
1 Introduction The rapid, unstoppable growth in the world population demands more energy, and thus, it has accelerated the industrialization and urbanization. This growth in the industrial sector has led to the shortage as well as pollution of the water resources. Industrial wastewater is the primary source of heavy metals (specific gravity > 5) like Cu, Zn, Pb, Cr, Fe, Cd, Ni, and Hg to these water resources [1]. This wastewater, when get mixed with these natural water resources, makes it hazardous and toxic to the aquatic animals, plants, and human being as well. The discharge of these chemical agents into the water bodies has endangered the equilibrium of the natural ecosystem. These genotoxic and mutagenic agents even can cause long-term disorders, and this may even pass to the future
* Monoj Kumar Mondal [email protected] 1
Department of Chemical Engineering and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005, India
generation as well [2]. However, the toxicokinetic and toxicodynamic parameters of these heavy metals primarily depend upon different physicochemical attributes. Thus to reduce the negative impact of these heavy metals, it is necessary to do the toxicity analysis befo
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