Abstract:

Due to its limited adsorption capacity for metal ions in aqueous solutions,alkali lignin is unsuitable for direct industry application as an absorbent of heavy metals.In this paper,a phosphorylation modification of alkali lignin was carried out,and the adsorption capacity of the phosphorylated alkali lignin (PAL) for Pb²⁺ was investi- gated by means of IR,particle charge detection,SEM and atomic absorption spectroscopy,followed with a mecha- nism exploration.The results indicate that (1) after the phosphorylation,the surface of lignin becomes coarse and porous,the specific surface area increases from 2. 12 to 11. 17m² /g,and the adsorption process becomes fast,with a higher adsorption capacity of Pb²⁺ ; (2) the adsorption mainly depends on the electrostatic interaction between Pb²⁺ and such negative functional groups as phosphate,phenolic hydroxyl and carboxyl,as well as on the ion ex- change between H⁺ and Pb²⁺ ; (3) the Pb²⁺ removal capacity of PAL is mainly affected by the PAL mass,the ini- tial mass concentration of Pb²⁺ ,the pH value and the temperature; and (4) the Pb²⁺ removal increases with the increase of PAL mass and pH value,and reaches the maximum 92. 36% at 30℃.

Key words: alkali lignin, phosphorylation, adsorption, electrostatic interaction, ion exchange