Increasing arsenic sorption on red mud by phosphogypsum addition.
Mining by-products have been tested as adsorbents for arsenic in order to reduce As bioavailability. This study evaluated a red mud (RM) treated with or without phosphogypsum (G) in order to improve its As retention. Red mud and G samples and their mixtures were chemically and mineralogically characterized to gather information concerning their composition, which is key for a better understanding of the adsorbent properties. Phosphogypsum was added to RM in the following proportions: 0, 1, 2, 5, 10, and 25% by weight. These mixtures were subjected to As adsorption and desorption and tested for their maximum adsorption capacity of As (AsMAC). Arsenic adsorption increased upon increasing the proportion of G added to RM. The AsMAC at pure RM reached 909 mg kg(-1), whereas the 75%-RM+25%-G mixture sorbed up to 3333 mg kg(-1) of As, i.e., a 3.5-fold increase in AsMAC. Using G in mixtures with RM increases the efficiency of As adsorption due to the presence of Ca(2+), which alters the charge balance of the adsorbent, leading to the formation of ternary complexes. Addition of G to RM is thus a promising technique to improve As retention, while providing additional value to both by-products, G and RM.
Department of Soil Science, Federal University of Lavras, Lavras, MG, CEP 37200-000, Brazil. Electronic address: guilhermlopes@yahoo.com.br.
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D000327:Adsorption; D000535:Aluminum / Q000737:chemistry; D000537:Aluminum Oxide / Q000737:chemistry; D001151:Arsenic / Q000737:chemistry*; D001938:Brazil; D002133:Calcium Sulfate / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005843:Geography; D007220:Industrial Waste; D007700:Kinetics; D008906:Mining; D010756:Phosphoric Acids / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*; D014131:Trace Elements; D014961:X-Ray Diffraction
D007220:Industrial Waste; D010756:Phosphoric Acids; D012987:Soil; D014131:Trace Elements; C077769:phosphogypsum; D010758:Phosphorus; D000535:Aluminum; C030242:phosphoric acid; D000537:Aluminum Oxide; D001151:Arsenic; D002133:Calcium Sulfate