Enhancement of Agrosoil Cd2+ Immobilization Efficiency through Incubation with Bamboo Sawdust/Rice Husk Biochar Blends: The Effect of Carbonization Temperature and Blending Ratio

Abstract

ABSTRACT Thermal modification of blended feedstocks has recently gained popularity, due to its importance in improving biochar yield and features, such as pore structure and adding extra functional groups than pristine ones and thus improving adsorption effectiveness against a range of pollutants. In this study, the biochar made up of blended bamboo sawdust and rice husk has been investigated on its effectiveness on Cd2+ sorption processes controlling the accessibility and mobility of this metal in agro-soil. In a set of batch experiments, the effect of a 10% w/w biochar (carbonized at 400°C and 700°C) to soil ratio at various blending ratios (1:1, 1:3, and 3:1) on the adsorption and desorption characteristics of Cd2+ in agricultural clay soil incubated for 60 days was investigated. The adsorption kinetics and isotherms were also studied to examine adsorption mechanism at pH of 8, initial solute concentration 200 mg/L, ionic strength of 0.01 M (NaNO3), Contact time of 180 min, and adsorbent dosage of 0.1 g. For adsorption kinetics, pseudo-first order, pseudo-second order, elovich, and intra-particle diffusion models were fitted, while Langmuir, Freundlich, Temkin, and Dubinin Radushkevich models were fitted in isotherm study. According to the findings, increasing the carbonization temperature (400–700°C) boosted the effectiveness of cadmium removal substantially (70–96%), the best adsorption capacity of 130 mg/g was obtained at 700°C. Meanwhile, the removal efficiency of biochar blending ratios was not significantly different. Similarly, as the carbonization temperature was increased, the rate of Cd2+ adsorption increased dramatically, whereas the rate of Cd2+ desorption dropped. Langmuir isotherm adsorption model and Pseudo-second order kinetic model were found to fit best (R2 = 0.99) on isotherm and kinetics studies, respectively. It can be concluded that employing blended feedstock biochar could improve soil immobilization efficiency for Cd2+ in agricultural fields.