The adsorption of phytate onto an Fe-Al-La trimetal composite adsorbent: kinetics, isotherms, mechanism and implication

Authors: ZHU, YUANRONG - Chinese Research Academy Of Environmental Sciences; LIU, ZHAN - Anhui Jianzhu University; LOU, KUN - Anhui Jianzhu University; XIE, FAZHI - Anhui Jianzhu University; He, Zhongqi; LIAO, HAIQING - Chinese Research Academy Of Environmental Sciences; GIESY, JOHN - Chinese Research Academy Of Environmental Sciences

Submitted to: Environmental Science: Water Research & Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2021
Publication Date: 11/1/2021
Citation: Zhu, Y., Liu, Z., Lou, K., Xie, F., He, Z., Liao, H., Giesy, J.P. 2021. The adsorption of phytate onto an Fe-Al-La trimetal composite adsorbent: kinetics, isotherms, mechanism and implication. Environmental Science: Water Research & Technology. 7(11):1971-1984. https://doi.org/10.1039/d1ew00318f.
DOI: https://doi.org/10.1039/d1ew00318f

Interpretive Summary: Phosphorus (P) is an element that is a nutrient essential for life and a major contributor to nonpoint-source pollution and eutrophication. Phytate is the most abundant organic phosphorus (P) in the environment and is also an important bioavailable P source for algal blooms in some lakes. In this study, a novel Fe-Al-La (FAL) trimetal composite adsorbent that is less costly to produce than La oxide alone and is also more environmentally friendly was developed. Phytate adsorption experiments, including adsorption kinetics; adsorption isotherms; thermodynamic parameters; and the effects of pH, anions, and dissolved organic matter (DOM), onto the FAL adsorbents were performed. Mechanisms of adsorption of phytate by FAL adsorbents are analyzed and discussed The results showed that the FAL adsorbents exhibited potential for removing both phytate and other phosphates during treatment of waste-waters including those from pig and poultry manures, and immobilizing these phosphate species present in overlying water and lake sediments.

Technical Abstract: Phytate is the most abundant organic phosphorus (P) in the environment and is also an important bioavailable P source for algal blooms in some lakes. A novel Fe-Al-La (FAL) tri-metal composite adsorbent was developed. Maximum adsorption capacity was 2.09 µmol m-2 at 298 K and a pH of 4. The dominant process for the adsorption of phytate by FAL adsorbents was surface chemical reactions mainly by monolayer coverage. The adsorption was best described by Langmuir isotherms, and its kinetics by a pseudo-second-order kinetic equation. Thermodynamic parameters indicated that adsorption of phytate by FAL adsorbents was a spontaneous and endothermic process. The adsorption capacity decreased with pH variation from 3.16 to 11.00, especially when pH > 9.0. The sequence of strength of competition of coexisting anions with phytate was CO32- > SO42- > NO3- > Cl-. Dissolved organic matter (DOM) also competed for adsorption sites with phytate on surfaces of the FAL adsorbents. Fourier transform infrared (FT-IR) spectroscopic and X-ray photoelectron spectroscopic (XPS) analyses showed that phytate had been adsorbed onto surfaces of the FAL adsorbents and that Fe, Al and La all participated in adsorption. Prepared FAL adsorbents exhibited potential for removing both phytate and other phosphate species during treatment of waste-waters including those from pig and poultry manures, and immobilizing these phosphate species present in overlying water and lake sediments. This study also indicated that eutrophication of lakes would increase potential of phytate to be a bioavailable form of P in blooming of algae.