Conversion of agricultural waste biomass resource into high-added-value composite and its potential for boosting synergistic removal of ammonia nitrogen in practical water

Agricultural production has long attracted attention for its high demand for resources and high damage to the environment. To address the high costs and impacts of nitrogen fertilizer overuse, a new method for treating ammonia nitrogen pollution in agricultural water bodies needs to be established to ensure water source safety and environmental quality, and to sustain agricultural production. This study involved pretreating oilseed rape straw (ORS) to extract waste biomass to functionalize with active inorganic bimetallic layer, which serves as the primary component for adsorbing ammonia nitrogen from both simulated and real wastewater. The hierarchical structure of the Cu-Al bimetallic hydroxide-functionalized waste ORS biomass (Cu-Al@ORS) is characterized by an abundance of nanosheet clusters on its surface, providing a large number of binding sites. Under the optimal conditions (pH 7.0, temperature 25 °C), the maximum removal efficiency towards ammonia nitrogen can reach 54.5 %. According to the adsorption kinetics fitting result, the adsorption of ammonia nitrogen by Cu-Al@ORS conforms well to the pseudo-second order kinetic model with an adsorption capacity of 87.11 mg/g and chemisorption is the rate-determining step in the adsorption process. Furthermore, the Cu-Al@ORS exhibits comparable adsorption stability and regeneration performance in practical applications. The removal efficiency declines to 49.89 % after the fifth cycle, which is significantly lower than the 67.57 % decrease observed in activated carbon. The practical application results suggest the potential of Cu-Al@ORS as a promising, cost-effective, and sustainable alternative to activated carbon for treating wastewater. The study focuses on the conversion of waste agricultural straw into biomass with ammonia nitrogen removal capabilities, offering a theoretical underpinning for the benign treatment, resource utilization, and carbon sequestration and emission reduction of agricultural waste biomass.