Phytic acid-modified corn stalks assisted by supercritical carbon dioxide for Cu2+ adsorption

Abstract

Heavy metal pollution poses a severe threat to aquatic ecosystems and human health, necessitating the urgent development of high-performance and sustainable adsorbents for effective removal. Corn stalks, as natural heavy metal ion adsorbents, face challenges such as low grafting efficiency and the requirement for significant amounts of chemical reagents during modification. In this study, supercritical carbon dioxide (scCO₂) was used as a medium to modify corn stalk (CS) with phytic acid (PA), producing a highly efficient Cu²⁺ adsorbent (SCCS-PA) for the removal of Cu²⁺ from aqueous solutions. The introduction of scCO₂ enhanced the grafting efficiency of corn stalks, reduced the use of organic solvents, and significantly improved their adsorption capacity. The effects of varying scCO₂ temperature, pressure, reaction time, and PA dosage on the modification degree and adsorption performance of SCCS-PA were systematically investigated. Under optimized conditions, the adsorption capacity of SCCS-PA was significantly higher than that of unmodified CS and CS-PA prepared in a DMF solution. The adsorption of Cu²⁺ by SCCS-PA followed the pseudo-second-order kinetics and Langmuir isothermal models, with a maximum adsorption capacity of 48.11 mg/g. The adsorption thermodynamics results indicate that the adsorption process is spontaneous. Multiple adsorption–desorption cycle experiments demonstrated that SCCS-PA possesses excellent regenerability. The bio-adsorbent developed in this study exhibited high efficiency and excellent regenerability for the removal of Cu²⁺ from water, showing great potential for practical applications.

Graphical abstract