A lignin-based nano-adsorbent for superfast and highly selective removal of phosphate

Abstract

The design of an environmentally benign cost-effective adsorbent for superfast removal of phosphate from wastewater is vital but remains a huge challenge. Herein, we have developed a recyclable, low-cost nanostructured bio-adsorbent, poly(ethyleneimine)-graft-alkali lignin loaded with nanoscale lanthanum hydroxide (AL–PEI–La), by a facile fabrication. AL–PEI–La was found to exhibit an excellent adsorption performance toward phosphate ions. For example, 94% of the phosphate ions from 40 mL of a solution containing 50 mg P L⁻¹ phosphate ions was removed in 60 min. Additionally, in a low phosphate concentration wastewater of 2.0 mg P L⁻¹, 95% of phosphate was removed in just 1 min and 99% of phosphate was removed in 15 min and the phosphate concentration dramatically decreased below 50 μg P L⁻¹, which met the standard of eutrophication prevention. The adsorption capacity of AL–PEI–La for phosphate ions was found to be 65.79 mg P g⁻¹, which is 33 times larger than that of lignin. AL–PEI–La shows strong anti-jamming capability in terms of pH value (3.0–9.0) and the co-existing ions of the aqueous solution exhibiting highly selective capacity for phosphate removal. The interactions between surface precipitation and ligand exchange are predominantly responsible for the adsorption process. Importantly, it shows a good reusability and 85.76% of the original adsorption capacity remains after 3 cycles. Thus, the as-designed nanostructured bio-adsorbent with exceptional adsorption effectiveness and efficiency is expected to find extensive applications for remediating the phosphate-contaminated waters.