1 IN-SITU REMOVAL OF ARSENIC FROM GROUNDWATER USING ...

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Total 72.5412 73.0886 62.2824The concentration of adsorbed Arsenic is higher at the surface of the sorbent although arsenichas apparently penetrated to the inner part of the particle, even if the particle has a large size(scale is indicated at the picture). Nevertheless, concentrations decrease from the outer to theinner side of the particle. Notice that the highest concentration in As coincides with the lowestconcentration in Fe suggesting that part of the Fe is reduced to a soluble Fe(II) form. Areductive precipitation is possible and probably coexisting with other removal mechanisms.6.2. Sorbent GEH 102Figure 8 shows the mapping of the concentrations for different elements (As, Ni, O and Fe) in aparticle of GEH 102 after it was exposed to arsenic sorption in a fixed bed column during 30days.Figure 8 – Mapping of concentrations in a particle of GEH102The following observations may be noticed:‐ Arsenic is captured around all the external surface of the sorbent particle constituting alayer with variable thickness;‐ The increase in arsenic concentrations coincide with a net depletion in oxygen;‐ Iron concentrations remain approximately constant inside the particle.Figure 9 presents another set of sorbent particles and the mapping of iron concentrations. It isnoticeable a decrease in the concentrations at the outer surface of the particles. Concentrationsin the inner part are approximately homogeneous although small heterogeneities with higherconcentrations can be noticed.10
Figure 9 – Iron concentrations in a set of particlesThe mapping of arsenic concentrations was also performed (Figure 10)Figure 10 – Mapping of As concentrationsSome facts:‐ Arsenic is captured through the exposed surface of the particles. If some particlespresent only a part of the external surface with higher arsenic concentrations it is due tothe fact that the particle was in contact with another (sorbent or sand) and the surfacedidn’t contact the arsenic solution;‐ One of the particles didn´t captured arsenic, probably due to the reasons alreadyexposed;‐ The thickness of the sorption layer may reach values as high as 40 m.One of the particles was selected for quantitative chemical analysis (Figure 11).11
Page 1 and 2: IN-SITU REMOVAL OF ARSENIC FROM GRO
Page 4 and 5: As in Solid Phase (mg/g)16141210864
Page 6 and 7: For the flowrate of 20 mL/min the r
Page 8 and 9: 6. Study of the sorption mechanisms
Page 12 and 13: Figure 11 - Selected particle and p
Page 14: Köber R., Daus B., Ebert M., Mattu

1 IN-SITU REMOVAL OF ARSENIC FROM GROUNDWATER USING ...

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