Efficient adsorption removal of Cd2+ from aqueous solutions by HNO3 modified bamboo-derived biochar

In this work porous biochar was prepared from bamboo powder by ZnCl2 chemical activation. The effects of preparation, modification and adsorption conditions on its removal performance of Cd²⁺ in simulated wastewater were investigated by static adsorption. The adsorption kinetics and isotherms of Cd²⁺ were further studied. The results showed that the good adsorption property was obtained over the biochar prepared under optimized preparation and modification conditions. The biochar reached the highest removal efficiency of 95.53% under optimum adsorption conditions. The adsorption process of Cd²⁺ was well in accordance with the pseudo-second adsorption kinetics equation, and the equilibrium adsorption capacity was up to 16.62 mg·g^-1. The Freundlich isothermal adsorption model better fitted compared with the Langmuir model for this adsorption system and the maximum adsorption capacity was as high as 44.54mg·g^-1. After four adsorption-desorption recycling, the adsorption removal percentage decreased a little, indicating that biochar had good regeneration performance. In short, this inexpensive porous biochar has the potential to become a practical adsorbent of cadmium.