Study on the Preparation of Biochar from Xinjiang Biomass Pyrolysis and Its Adsorption Characteristics for Water Pollutants

Abstract

This study examines the adsorption capabilities of six types of biochars, prepared via pyrolysis of biomass materials sourced from Xinjiang, for removing pollutants from water. The results demonstrate that higher pyrolysis temperatures facilitate more complete decomposition of organic components within the feedstock, leading to increased pore size and specific surface area of the biochars. This enhancement significantly boosts the adsorption efficiency of methylene blue (MB) by the biochars. Efficient and well-structured porous biochars can be obtained at 700 °C; notably, biochars produced at 900 °C achieve MB removal efficiencies exceeding 99.5%. Furthermore, cyclic adsorption performance tests targeting MB indicate that, with the exception of corn cob biochar pyrolyzed at 900 °C, all other biochars maintain a removal rate of at least 71.4% after four cycles. The rich internal porous structure of the biochars and the presence of oxygen-containing functional groups on their surfaces enable those synthesized at 900 °C to achieve high equilibrium adsorption capacities for lead ions (Pb²⁺) in water within 30 min, averaging or surpassing 102.2 mg/g. Notably, cotton stalk biochar, which is abundant in oxygen-containing functional groups, exhibits a maximum equilibrium adsorption capacity for Pb²⁺ of up to 196.0 mg/g. Importantly, during the four cycles of reuse, both cotton stalk biochar and bamboo biochar pyrolyzed at 900 °C display relatively stable adsorption characteristics for Pb²⁺. Kinetic model analysis reveals that the adsorption processes of MB and Pb²⁺ by these biochars conform to both pseudo-first-order and pseudo-second-order kinetic models. These findings provide valuable guidance for the application of biochars in water treatment fields.