Biosorption of Heavy Metal and Organic Dyes from Textile Wastewater using Algal Derived Biochar

Abstract

Textile industries release effluent that contains the vast majority of heavy metals and dyes in which Cr (VI) and Congo red Dye is a toxic carcinogenic element that causes an environmental problem. The work aims to synthesize algal-derived biochar using slow pyrolysis at an operating temperature of 500 ℃, a heating rate of 10 ℃/min and a residence time of 60 min and use it as an adsorbent to remove Cr (VI) and Congo red Dye. The batch experiment was carried out using different concentrations of Cr (VI) and Congo red Dye (1, 10, 25, 50, 100, 125, 150 and 200 ppm) at different intervals of time (2.5, 5, 10, 15, 30, 60, 120 and 240 min). The maximum removal percentage of Cr (VI) is 97.88 % and Congo Red Dye is 96.14029 % for the metal concentration of 1 ppm exhibiting non-linear adsorption isotherm (Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin models) and kinetic models (pseudo-first order, pseudo-second order, nth order, and intra-particular diffusion) were analyzed using a solver add-in of Microsoft Excel. According to the results, the Langmuir isotherm model (R2 = 0.999, R2=0.996) and pseudo-nth order models are suitable to describe the monolayer adsorption and the process kinetics, respectively. The maximum adsorption capacity of algal biochar to adsorb is 186.94 mg/g for Cr (VI) and 179.9524 mg/g for Congo red Dye. For the prediction of optimal removal efficacy, an artificial neural network of the MLP-2-7-1 (Cr (VI) and MLP-2-5-1(Congo Red Dye) model was used. The results obtained are useful for future work using algal biochar as an adsorbent of Cr (VI) and Congo Red Dye from textile wastewater to achieve sustainable development goals.