Characterizing Aqueous Cd2+ Removal by Plant Biochars from Qinghai–Tibet Plateau

Increased anthropogenic activities have caused cadmium pollution in Qinghai–Tibet Plateau, which is harmful to human health. This paper investigated aqueous Cd2+ adsorption using biochar of three typical vegetation types in cold and arid areas of the Qinghai–Tibet Plateau: (i) Chinese wolfberry (GBB), (ii) highland barley (QBB), and (iii) seabuckthorn (SBB). In order to investigate the effect of pyrolysis temperature on the performance of biochar for cadmium adsorption, three types of biochar were prepared at 350 °C, 500 °C, and 650 °C. The as-prepared biochar was characterized by scanning electron microscopy (SEM), Thermogravimetric (TG), Fourier transform infrared spectroscopy (FT-IR), and Brauer–Emmett–Teller (BET) analysis. The results showed that the biochar prepared at 650 °C had the best adsorption capacity. Compared with QBB and SBB, the GBB had a higher Cd2+ adsorption capacity of 19.48 mg/g. Moreover, the effects of biochar dosage, experimental temperature, and biochar preparation temperature on the adsorption of Cd2+ by biochar and the interaction between the factors were investigated using Box–Behnken Design (BBD). As a result, the amount of biochar dosage showed the most obvious influence on Cd2+ adsorption capacity, followed by sample preparation temperature and experimental adsorption temperature. This study paves the way for the design of biochar for Cd2+ adsorption in wastewater.