Metal removal capacity and kinetics of Biochar from aqueous solutions

Abstract

Biochar prepared through pyrolysis by agricultural wastes has gained great attention as a cost-effective treatment for wastewater i.e., metal contaminated. Adsorption effect of biochar in reducing the heavy metal’s contamination is quite remarkable. In our current study, the effectiveness of corn cob and sugarcane bagasse as economical bio-adsorbent for the exclusion of metals (Cd, Pb, Ni and Cu) from aqueous medium was examined. In order to analyze the structure and composition of biochar, X-Ray Diffractometer, Fourier Transform Infrared Spectrometer and Scanning Electron Microscope were used. The physiochemical characteristics of biochar like surface area, porosity, cation exchange capacity (CEC), total carbon (TC) and pH were determined. The efficiency of biochar was examined at four different conditions i.e., different metal concentrations, pH change, contact time and dosage concentration in a batch studies. For the purpose of estimation of adsorption parameters, the Langmuir model and Freundlich equation were used. The separation factor (RL) showed that the values lied in the range of 0 and 1, representing that the adsorption by biochar is productive. The optimum dosage for metal adsorption can be recommended as 50gL-1. The optimum adsorption conditions were found at 6.5 and 5.5 pH, 1.5g adsorbent dose and at 180minutes equilibrium time, for both corn cob and sugarcane bagasse. At pH 6.5, the maximum adsorption capacities of Cd, Pb, Ni and Cu were found maximum i.e., 4.60, 11.34, 15.71 and 11.96 mgkg-1 for corn cob while for sugarcane bagasse, the maximum adsorption observed was 4.55, 8.96, 15.46 and 12 mgkg-1, respectively. The metal adsorption kinetics was analyzed via four different types of kinetic model i.e., pseudo-second-order. Hence, for the purpose of heavy metals elimination from wastewater, biochar of sugarcane bagasse and corncob could be utilized as economical adsorbent. Corn cob derived biochar showed the more pronounced activity in the removal of metal contamination as compared to sugarcane bagasse biochar.