Progress on the adsorption characteristics of nZVI and other iron-modified biochar for phosphate adsorption in water bodies

The issue of water body eutrophication induced by phosphorus is escalating, and there is an urgent need for materials that can control phosphate in water bodies. Biochar is often used as an adsorption material for phosphate removal from water bodies because of its high efficiency, strong stability, and low cost. However, the phosphate adsorption capacity of pristine biochar is limited, and iron and its compounds are often loaded to overcome this limitation and improve the adsorption effect. The current status of the use of nanoscale zero-valent iron (nZVI) and other iron-modified biochar in the treatment of eutrophic water is summarized. The preparation process of nanoscale zero-valent iron-modified biochar was introduced. The adsorption mechanism of nZVI and other iron-modified biochar in phosphorus removal from water was explained (mainly related to the roles of electrostatic, precipitation, complexation, ion exchange, etc.); the effects of factors such as dosage, pH value, and initial phosphate concentration on the adsorption of phosphate by iron-modified biochar were analyzed; and the possibility of reusing iron-modified biochar after adsorbing phosphate was pointed out. Based on the above research, the problems and future development directions of nZVI and other iron-modified biochars were proposed. This study provides a theoretical basis for the treatment of eutrophication in water bodies and the utilization of solid waste resources.