Facile Modification of Biochar Derived from Agricultural Straw Waste with Effective Adsorption and Removal of Phosphorus from Domestic Sewage

In recent decades, straw waste is the major byproduct around agriculture that has become one of the factors of environmental pollution. The purpose of this study is to reuse waste straw to develop a new green and highly efficient biomass-based adsorbent for phosphorus removal. To attain this aim, Mg–Al bimetallic oxide/straw fiber (Mg–Al/SF) with hierarchical structure was successfully synthesized by hydrothermal method using waste straw as the biomass carbon precursor and Mg–Al/SF was applied as adsorbent in the removal of phosphorus from wastewater. The morphology, composition and structure of the adsorbent was well supported by several characterizations. The prepared biomass-based adsorbent showed outstanding adsorption performance. Maximum adsorption capability of Mg–Al/SF towards phosphorus from the Langmuir isotherm model was fitted out to be 89.37 mg/g. The related kinetics and isotherm study for the adsorption process were explored in detail. The proposed adsorbent exhibited good reusability that the removal of phosphorus remained above 72% after 5 cycles. In addition, thermodynamic study was carried out to further investigate the phosphorus removal mechanism, which was the synergistic combination of surface adsorption and chemical adsorption. The removal of total phosphorus in actual domestic sewage (Total phosphorus, TP, 0.8–1.1 mg/L) were investigated. The results indicated that the prepared Mg–Al/SF has excellent TP adsorption and recycling performance, and the adsorption and stability performance are significantly higher than that of the commercial activated carbon. The interactions between biomass material with large surface area and metal oxide provides great potential for the real application in the water treatment. Furthermore, it also presents a feasible and efficient practical example of increasing the use of agricultural waste.