http://netedu.xauat.edu.cn/jpkc/netedu/jpkc2009/szylyybh/content/wlzy/1/Review%20of%20Arsenic%20in%20natural%20water%20-%20Smedly.pdf

A review of the source, behaviour and distribution of arsenic in natural waters

Preface.- Contributors.- List of Abbreviations.- Section 1: Basic Principles: Introduction.-Sources of Heavy Metals and Metalloids in Soils.- Chemistry of Heavy Metals and Metalloids in Soils.- Methods for the Determination of Heavy Metals and Metalloids in Soils.- Effects of Heavy Metals and Metalloids on Soil Organisms.- Soil-Plant Relationships of Heavy Metals and Metalloids.- Heavy Metals and Metalloids as Micronutrients for Plants and Animals.-Critical Loads of Heavy Metals for Soils.- Section 2: Key Heavy Metals And Metalloids: Arsenic.- Cadmium.- Chromium and Nickel.- Cobalt and Manganese.- Copper.-Lead.- Mercury.- Selenium.- Zinc.- Section 3: Other Heavy Metals And Metalloids Of Potential Environmental Significance: Antimony.- Barium.- Gold.- Molybdenum.- Silver.- Thallium.- Tin.- Tungsten.- Uranium.- Vanadium.- Glossary of Specialized Terms.- Index.

Heavy metals in soils : trace metals and metalloids in soils and their bioavailability

New generation adsorbents for water treatment.

Because of its toxicity, arsenic is of considerable environmental concern. Its solubility in natural systems is strongly influenced by adsorption at iron oxide surfaces. The objective of this study was to compare the adsorption behavior of arsenite and arsenate on ferrihydrite, under carefully controlled conditions, with regard to adsorption kinetics, adsorption isotherms, and the influence of pH on adsorption. The adsorption reactions were relatively fast, with the reactions almost completed within the first few hours. At relatively high As concentrations, arsenite reacted faster than arsenate with the ferrihydrite, i.e., equilibrium was achieved sooner, but arsenate adsorption was faster at low As concentrations and low pH. Adsorp tion maxima of approximately 0.60 (0.58) and 0.25 (0.16) molAs molFe-1 were achieved for arsenite and arsenate, respectively, at pH 4.6 (pH 9.2 in parentheses). The high arsenite retention, which precludes its retention entirely as surface adsorbed species, indicates the likel...

Arsenite and Arsenate Adsorption on Ferrihydrite: Kinetics, Equilibrium, and Adsorption Envelopes

https://pubag.nal.usda.gov/download/27113/PDF

Mechanisms of Arsenic Adsorption on Amorphous Oxides Evaluated Using Macroscopic Measurements, Vibrational Spectroscopy, and Surface Complexation Modeling.

The molecular structure of ions retained on mineral surfaces is needed to accurately model their sorption process and to determine their stability. Extended X-ray absorption fine structure (EXAFS) spectroscopy was used in this study to deduce the local coordination environment of two environmental contaminants, arsenate and chromate, on the mineral goethite (α-FeOOH). Based on the oxyanion−Fe distances, it was concluded that three different surface complexes exist on goethite for both oxyanions:  a monodentate complex, a bidentate-binuclear complex, and a bidentate-mononuclear complex. At low surface coverages, the monodentate complex was favored while at higher coverages the bidentate complexes were more prevalentthe bidentate-binuclear complex appears to be in the greatest proportion at these highest surface coverages. Therefore, modeling efforts for chromate or arsenate retention on goethite need to consider a monodentate complex at very low coverages, both the monodentate and bidentate complexes at in...

Arsenate and Chromate Retention Mechanisms on Goethite. 1. Surface Structure

The kinetics of arsenate and chromate adsorption/desorption on goethite (α-FeOOH) were investigated using a pressure-jump (p-jump) relaxation technique. Information provided by this technique was used to elucidate the fate of arsenate and chromate in natural environments. Chemical relaxations resulting from rapidly induced pressure changes were monitored via conductivity detection. The adsorption/desorption of these oxyanions on goethite involved a double relaxation event. The proposed mechanism for the adsorption of arsenate and chromate on goethite is a two-step process resulting in the formation of an inner-sphere bidentate surface complex. The first step, associated with the fast τ values, involved an initial ligand exchange reaction of aqueous oxyanion species H2AsO4- or HCrO4- with OH ligands at the goethite surface forming an inner-sphere monodentate surface complex. The subsequent step, associated with the slow τ values, involved a second ligand exchange reaction, resulting in the formation of an ...

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Paul R. Grossl

Papers

Arsenate and Chromate Retention Mechanisms on Goethite. 1. Surface Structure

Arsenate and Chromate Retention Mechanisms on Goethite. 2. Kinetic Evaluation Using a Pressure-Jump Relaxation Technique