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

Arsenic removal from water/wastewater using adsorbents—A critical review

Arsenic derived from natural sources occurs in groundwater in many countries, affecting the health of millions of people. The combined effects of As(V) reduction and diagenesis of iron oxide minerals on arsenic mobility are investigated in this study by comparing As(V) and As(III) sorption onto amorphous iron oxide (HFO), goethite, and magnetite at varying solution compositions. Experimental data are modeled with a diffuse double layer surface complexation model, and the extracted model parameters are used to examine the consistency of our results with those previously reported. Sorption of As(V) onto HFO and goethite is more favorable than that of As(III) below pH 5−6, whereas, above pH 7−8, As(III) has a higher affinity for the solids. The pH at which As(V) and As(III) are equally sorbed depends on the solid-to-solution ratio and type and specific surface area of the minerals and is shifted to lower pH values in the presence of phosphate, which competes for sorption sites. The sorption data indicate tha...

Comparison of arsenic(V) and arsenic(III) sorption onto iron oxide minerals: implications for arsenic mobility.

Remediation of heavy metal(loid)s contaminated soils - To mobilize or to immobilize?

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 adsorption and stability of arsenite [As(III)] on goethite (α-FeOOH) was investigated using a combination of standard batch techniques and X-ray absorption spectroscopy (XAS). The reactivity of As(III) with α-FeOOH at varying pH and As(III) concentration provided macroscopic evidence for strong complexation on the α-FeOOH surface. Extended X-ray absorption fine structure (EXAFS) spectroscopy gave an average As(III)−Fe interatomic distance of 3.378 ± 0.014 A, which is indicative of bidentate binuclear bridging As(III) complexes on the α-FeOOH surface and which is similar to other oxyanions which adsorb on α-FeOOH by an inner-sphere mechanism. X-ray absorption near-edge structure (XANES) analysis indicated that the As(III)−α-FeOOH surface complex is stable toward heterogeneous oxidation to As(V), as determined by the energy position of the X-ray absorption edge. The structural information from EXAFS was included in the description of As(III) adsorption on the α-FeOOH surface using a surface complexation...

/pdf/surface-structures-and-stability-of-arsenic-iii-on-goethite-2ua8p5e4js.pdf

Surface Structures and Stability of Arsenic(III) on Goethite: Spectroscopic Evidence for Inner-Sphere Complexes

Inorganic arsenite (As(III)) and arsenate (As(V)) are toxic pollutants that are transported in surface and ground waters and can adsorb on soil and sediment mineral surfaces. Because of the importance of adsorption reactions in determining the overall mobility of arsenic, we investigated the adsorpt

Arsenic(iii) and Arsenic(v) Adsorption on Three California Soils

Molybdenum adsorption behavior was investigated on a variety of crystalline and X-ray amorphous aluminum and iron oxide minerals, clay minerals, and arid-zone soils as a function of solution pH, molybdenum concentration, ionic strength, particle concentration, competing anion concentrations, and

Factors affecting molybdenum adsorption by soils and minerals

Anion adsorption on the aluminum oxide, gibbsite, was investigated as a function of solution pH (3―11) and equilibrium solution Mo (3.13, 31.3, or 313 μmol/L), P (96.9 μmol/L), or S (156 μmol/L) concentration. Adsorption of all three anions decreased with increasing pH. Electrophoretic mobility measurements indicated a downward shift in point of zero charge, indicative of an inner-sphere adsorption mechanism for all three anions. The constant capacitance model, having an inner-sphere adsorption mechanism, was able to describe Mo and P adsorption; whereas the triple-layer model with an outer-sphere adsorption mechanism was used to describe S adsorption. Competitive adsorption experiments showed a reduction of Mo adsorption at a Mo/P ratio of 1:30 and 1:300 but no reduction at a Mo/S ratio of 1 :52 and 1:520. These concentrations are realistic of natural systems where Mo is found in much lesser concentrations than P or S. Using surface complexation constants from single-ion systems, the triple-layer model predicted that even elevated S concentrations did not affect Mo adsorption. The constant capacitance model was able to predict the competitive effect of P on Mo adsorption semiquantitatively.

https://www.ars.usda.gov/ARSUserFiles/20360500/pdf_pubs/P2304.pdf

Competitive Adsorption of Molybdenum in the Presence of Phosphorus or Sulfur on Gibbsite

Boron (B) adsorption on two arid-zone soils from the San Joaquin Valley of California was investigated as a function of equilibrium solution B concentration (0–250 mg L j1 ), solution pH (3–12), and electrical conductivity (EC, 0.3 or 7.8 dS m j1 ). Boron adsorption on both soils increased with increasing pH, reached a maximum near pH 9, and decreased with further increases in pH. Boron adsorption as a function of solution pH was independent of solution salinity from pH 3 to 9. Above pH 9, B adsorption was increased from the solution of higher EC. Boron adsorption for both soils as a function of solution B concentration conformed to the Langmuir adsorption isotherm equation. The B adsorption maxima obtained with the Langmuir equation for both EC were not statistically significantly different at the 95% level of confidence. The constant capacitance model, a surface complexation model, was able to describe B adsorption as a function of solution B concentration and solution pH. Boron adsorption was predicted using the soil chemical properties surface area, organic carbon content, inorganic carbon content, and aluminum oxide content. The predictions are suitable for transport modeling and will be used to describe B movement in large soil columns. Our results are advantageous because they indicate that under agricultural conditions (pH 3–9), B adsorption can be described without consideration of changes in soil solution salinity. (Soil Science 2008;173:368–374)

Sabine Goldberg

Papers

Surface Structures and Stability of Arsenic(III) on Goethite: Spectroscopic Evidence for Inner-Sphere Complexes

Arsenic(iii) and Arsenic(v) Adsorption on Three California Soils

Factors affecting molybdenum adsorption by soils and minerals

Competitive Adsorption of Molybdenum in the Presence of Phosphorus or Sulfur on Gibbsite

Influence of soil solution salinity on boron adsorption by soils