Enhancement of selective adsorption of Cr species via modification of pine biomass

• DOI: 10.1016/j.scitotenv.2020.143816
• Publication Date: 2020-11-26T01:00:52Z
• Authors: Jingjing Zhao; Roberto Boada; Giannantonio Cibin; Cristina Palet
• Keywords: Chromium; Water Pollutants, Chemical/analysis; Biomass/biochar; XAS; Hydrogen-Ion Concentration; 01 natural sciences; Water remediation; X-Ray Absorption Spectroscopy; Adsorption mechanism; SDG 3 - Good Health and Well-being; Chromium/analysis; Charcoal; Chromium species; Adsorption; Biomass; SDG 6 - Clean Water and Sanitation; SDG 12 - Responsible Consumption and Production; Water Pollutants, Chemical; 0105 earth and related environmental sciences

Pine biomass (Pine), pine gasification biochar (PG) and pine biomass loaded with TiO2 (Pine/TiO2) were used as sorbent materials to remove Cr(III) or Cr(VI) ions from aqueous solutions. Our results showed that Pine/TiO2 had an improved adsorption capacity respect to Pine being the adsorption capacity for Cr(VI), 12.8 mg/g, much larger than for Cr(III), 1.23 mg/g. On the other hand, PG showed much higher adsorption for Cr(III), 12.4 mg/g, than Pine/TiO2, and negligible adsorption for Cr(VI). To understand this species-dependent adsorption behavior, the adsorption mechanisms, sorbents morphology and functional sites were characterized using a multi-technique approach. The chemical state and local coordination structure of the adsorbed Cr species was studied by X-ray absorption spectroscopy (XAS). Our results show that the adsorption of Cr(III) occurred mainly through cation exchange with mineral elements in PG biochar, whereas the Cr(III) adsorption by functional groups (carboxyl and hydroxyl groups) dominate in the biomass sorbent. The enhancement of Cr(VI) adsorption in Pine/TiO2 can be explained by the presence of TiOH2+groups present in the surface of the TiO2 microparticles. X-ray absorption spectroscopy (XAS) results reveal that Cr(VI) reduces to Cr(III) after being adsorbed by the sorbent materials.