LI Wenbin, YE Yong, DENG Hongyan, HU Yafei, Wang Dan, CHEN Xingyu, HE Haixia, YI Huiyu

（College of Environmental Science and Engineering, China West Normal University, Nanchong Sichuan 637009, China）

Abstract: To investigate the effect of biochar-based amphoteric clays (BAC) on the Cu2+ adsorption by purple soil, different BAC are added into purple soil with a mass ratio of 1% and 2% to form mixed soil samples. BAC is prepared by loading 0%, 50% and 100% CEC dodecyl dimethyl betaine modified bentonites on two biochars that derived from xerophilic and hydrophytic alternanthera philoxeroides. The effect of pH, ionic strength and temperature on Cu2+ adsorption by the tested soils was studied using the batch method, and Cu2+ adsorption and thermodynamic characteristics of tested samples under the optimal conditions were analyzed. The results showed that: (1) in the pH range of 2-5, the adsorption amount of Cu2+ on each soil sample are positively correlated with the increasing pH. The adsorption amount of Cu2+ on the tested samples increase first and then decrease with the increasing ionic strength, and presents the highest adsorption amount at 0.1 mol/L. Cu2+ adsorption by tested samples enhance with increasing temperature in the range of 10-40 °C. (2) under the optimum condition of pH=2, ionic strength of 0.1 mgl/L, and temperature of 40 °C, the adsorption isotherms of Cu2+ by different samples are all followed with the Langmuir model, and the maximum adsorption amount (qm) is between 160.79and 247.12 mmol/kg. After addition of 1% and 2% BAC, qm of different soil samples is 1.35-1.74 times and 1.57-2.02 times than that of raw purple soil, respectively. Adding xerophilic biochar-based materials and a 2% addition ratio achieves the highest Cu2+ adsorption. (3) Cu2+ adsorption by each soil sample is a spontaneous, endothermic, and entropy-increasing reaction process.

Keywords: biochar; amphoteric clay; purple soil; Cu2+; adsorption amount

EARTH AND ENVIRONMENT Vol.48, No.5, Tot No.337, 2020, Page 558-566