Professor University of Alberta Edmonton, Alberta, Canada
Abstract: There is a growing demand for biodegradable and sustainable materials, particularly those sourced from agricultural or industrial by-products, for use in wastewater treatment. This study introduces a novel approach for developing a sponge adsorbent derived exclusively from pea protein (peaAS-PEI) using a liquid foam templating for the removal of heavy metals. The pore size, surface area, and mechanical strength of the sponge were modulated by the extent of protein hydrophobic aggregation induced by ammonium sulfate (AS) immersion based on salting-out effect. Raising AS concentration from 10% to 20% led to an increase in surface area from 30.69 to 127.41 m²/g and compressive stress from 151.02 ± 8.73 kPa to 316.10 ± 13.87 kPa at 90% strain. Polyethyleneimine (PEI) grafting introduced additional amine groups for heavy metal adsorption and the porosity of the sponge increased from 86.9% to 90.3% upon surface modification. As a result, the PEI-modified sponge showed favorable adsorption performance of Cu(II), Zn(II), and Ni(II) ions with the maximum sorption capacity of 67.07, 115.61 and 55.86 mg/g, respectively. The adsorption kinetics and isotherm study suggested that chemisorption played more significant role in the adsorption process, occurring on a homogeneous surface with a finite number of monolayer active sites. Reusability tests for peaAS-PEI sponge revealed that its adsorption capacity could be well maintained over five successive adsorption–desorption cycles. The pea protein sponge also exhibited excellent biodegradability in soil within 28 days with weight loss by 86.1% and 67.5% before and after PEI grafting. Together, these results indicate the great potential of affordable and sustainable PEI-modified pea protein sponges for remediation of water polluted with copper, zinc, and nickel ions.
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