La-Ca-quaternary amine-modified straw adsorbent for simultaneous removal of nitrate and phosphate from nutrient-polluted water

Nitrates and phosphates accumulate in waterbodies and cause eutrophication, reduce the self-purification capacity of the water body, and decrease the dissolved oxygen, thereby causing the death of aquatic organisms. Simultaneous removal of nitrate and phosphate from water is challenging to achieve but is essential for improving the ecological environment and reducing public health hazards. In this study, we developed a novel adsorbent, La/Ca-loaded modified straw (La-Ca-MWS), for the simultaneous removal of nitrate and phosphate from water. Quaternary amine and La/Ca bimetallic groups were employed for nitrate and phosphate adsorption, respectively. The adsorption isotherms and kinetics as well as solution pH effects were investigated in single and binary pollutant systems. Nitrate and phosphate weakly inhibited each other’s adsorption on La-Ca-MWS in the binary system, and their adsorption capacities were 68.66 and 84.72 mg g−1, respectively. La-Ca-MWS showed excellent adsorption capacity over the pH range 3–10. After nine adsorption and desorption cycles in a 10 % NaOH–NaCl solution, the adsorption efficiency remained > 85 % in the adsorbent regeneration test. This bifunctional adsorption site-modified straw adsorbent has practical applications in nitrate and phosphate removal from wastewater. We expect that our findings will promote the development of multifunctional adsorbents in the future.