Enhanced recovery of arsenite sorbed onto synthetic oxides by l-ascorbic acid addition to phosphate solution: calibrating a sequential leaching method for the speciation analysis of arsenic in natural samples

• Published in: Water research (Oxford) 2006-06, Vol.40 (11), p.2168-2180
• Main Authors: Bok Jung, Hun, Zheng, Yan
• Format: Article
• Language: English
• Subjects: Adsorption; Anaerobiosis; Applied sciences; Arsenic; Arsenic - chemistry; Arsenic - isolation & purification; arsenites; ascorbic acid; Ascorbic Acid - chemistry; Calibration; chemical speciation; Exact sciences and technology; extraction; Ferric Compounds - chemistry; Hydrogen-Ion Concentration; Iron Compounds - chemistry; iron oxides; l-ascorbic acid; leaching; Manganese Compounds - chemistry; manganese oxides; Minerals; Other industrial wastes. Sewage sludge; Oxidation; Phosphate; Phosphates - chemistry; polluted soils; Pollution; sediment contamination; Sequential leaching; soil pollution; Sorption; Speciation; Wastes; Water Pollutants, Chemical - isolation & purification; Water Purification - methods; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2006.03.032

Stripping voltammetry capable of detecting 0.3 μg/L arsenate and arsenite was applied for speciation analysis of arsenic sorbed onto synthetic ferrihydrite, goethite at As/Fe ratio of ∼1.5 mg/g with or without birnessite after sequential extraction using 1 M phosphate (24 and 16 h) and 1.2 M HCl (1 h). Precautions to avoid oxygen were undertaken by extracting under anaerobic conditions and by adding 0.1 M l-ascorbic acid to 1 M NaH 2PO 4 (pH 5). Addition of l-ascorbic acid did not reduce As(V) to As(III). The recovery rate for As(III) using l-ascorbic acid for extraction (pH 5) but not for adsorption was 81% and 74% of total sorbed As, and was 99% and 97% of extracted As for ferrihydrite and goethite, respectively. Birnessite oxidized most As(III) during the adsorption procedure. l-ascorbic acid used both in adsorption and extraction procedures improved the recovery of As(III) to 79–94% for ferrihydrite–birnessite and 57–94% for goethite–birnessite systems with Fe/Mn ratios of 7, 70, 140 and 280 g/g.