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Interfacial Solid-Phase Chemical Modification with Mannich Reaction and Fe(III) Chelation for Designing Lignin-Based Spherical Nanoparticle Adsorbents for Highly Efficient Removal of Low Concentration Phosphate from Water

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journal contribution
posted on 15.06.2017, 00:00 by Xiaogang Luo, Chao Liu, Jun Yuan, Xingrong Zhu, Shilin Liu
Advanced adsorption of low concentration phosphate by low cost lignin-based adsorbents from water or wastewater is an economic and effective way to prevent the occurrence of eutrophication. In this work, lignin, a waste material recovered from black liquor, was treated with a simple interfacial solid-phase chemical modification method to design a high efficiency phosphate adsorbent. First, the lignin was modified by triethylenetetramine (TETA) with the Mannich reaction, and then Fe­(III) was chelated onto the aminated lignin. An efficient low concentration phosphate adsorption was observed by the kinetics experiments, which followed pseudo-second-order kinetically. The adsorption isotherms and thermodynamics were examined. This adsorbent was characterized by FTIR, SEM, particle size analysis, ζ potential analysis, and XPS. FTIR and XPS analyses indicated that iron atom was the binding site for phosphate adsorption. SEM pictures suggested that the adsorbent was uniformly ball-shaped and the particle size was about 450 nm. Both the adsorption experiments and characterization demonstrated that the phosphate adsorption mechanism of Fe­(III)-complexed lignin (Fe-CL) followed the complexation mechanism between iron and phosphate on Fe-CL. This study implied that biomass-based lignin could be used as a potential adsorbent for efficient removal of low concentration phosphate from water or wastewater.