Bionic-inspired La–Zn(4,4′-dipy)(OAc)2/bacterial cellulose composite membrane for efficient separation of nitrogen and phosphorus in water

Abstract Phosphorus and nitrogen flow to water leads to eutrophication and depletion of reserves. Bionic-inspired tannin modification is proposed for preparing a tannin-modified La–Zn(4,4′-dipy)(OAc)2/bacterial cellulose composite membrane for simultaneous adsorption of total phosphorus and ammonia nitrogen in water. Its physical and chemical properties were characterized by XRD, SEM, FT-IR, TGA and other characterization methods. La–Zn(4,4′-dipy)(OAc)2 nanomaterial achieved effective adhesion on the tannin-modified bacterial cellulose membrane. Adsorption experiments showed that the composite membrane could both adsorb total phosphorus and ammonia nitrogen, and adsorption capacity of ammonia nitrogen was better than that of total phosphorus. The maximum adsorption capacities of ammonia nitrogen and total phosphorus were 482.35 mg/g and 374.71 mg/g. In the binary solution, the adsorption capacity of the composite membrane to ammonia nitrogen and total phosphorus decreased, but the adsorption capacity to phosphorus decreased slightly. Results of adsorption experiments showed that the adsorption process of nitrogen and phosphorus by the composite membrane belonged to single-layer adsorption, and the calculation results of the kinetic equation were in accordance with the quasi-second-order, and the adsorption equilibrium of the composite membrane was reached within 360 min. In short, the composite membrane had a better adsorption and separation effect both on ammonia nitrogen and total phosphorus.