Biopolymer cryogels for enhanced adsorption of valuable metals from multi-metal waste after flocculation and precipitation

Author(s)

Braga, Victor H. A. ; Fuentes, Dairon P. ; Oliveira, Pedro, V ; Petri, Denise F. S.

• Document type: Journal article
• Source: JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING; v. 12, n. 5, p. 12-pg., 2024-10-01.

Abstract

This study focused on the treatment of a multi-metal waste sourced from laboratory settings, containing the mixture of Cr3+, Mn2+, Co2+, Fe3+, Ni2+, Cu2+, Zn2+, Sr2+, Hg2+, and Pb2+, at pH 1.0. The combination of flocculation with a polycation and subsequent precipitation with NH4OH removed Cr3+, Mn2+, Co2+, Fe3+, Zn2+, Hg2+, and Pb2+ as solid particles. These particles were separated from the supernatant and incorporated into cementitious pastes, thereby mitigating the leaching of hazardous ions into water. Ni2+, Cu2+, Sr2+ ions remained as soluble complexes in the supernatant that passed through fix-bed columns packed with cryogels composed of carboxymethyl cellulose (CMC) or chitosan (CHI), both reinforced with sugarcane bagasse (BG) microparticles. Among these cryogels, the composition featuring a mass ratio of 1:1 between CMC and BG (CMCBG50) exhibited superior efficacy in metal removal, particularly in adsorbing Cu2+ ions, a metal of significant economic interest. Breakthrough curves for the adsorption of Cu2+ on CMCBG50 indicated that the highest adsorption capacity of similar to 44 mg/g was achieved at flow rate of 1 mL/min and 0.2 g of adsorbent. FTIR-ATR, SEM-EDS and X-ray fluorescence analyses allowed proposing an adsorption mechanism based on metal-OH chelation and metal-carboxylate interactions. The spent CMCBG50 adsorbents were pyrolyzed employing a CO2 laser. This preliminary study indicated a substantial reduction in the electrical resistance of the pyrolyzed material, approximately fivefold compared to the pristine material. This outcome indicates a promising path to meet the principles of the circular economy practices, wherein waste can be sustainably reused.a (AU)

• FAPESP's process: 09/08584-6 - Supramolecular chemistry and nanotechnology
• Grantee: Henrique Eisi Toma
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 18/13492-2 - Synthetic and natural scaffolds applied to regenerative medicine
• Grantee: Luiz Henrique Catalani
• Support Opportunities: Research Projects - Thematic Grants