Abstract
Removal of arsenic from water reservoirs is the issue of great concern in many places around the globe. As adsorption is one of the most efficient techniques for treatment of As-containing media, thus the present study concerns application of iron oxides-hydroxides (akaganeite) as adsorbents for removal of this harmful metal from aqueous solution. Two types of akaganeite were tested: synthetic one (A) and the same modified using hexadecyltrimethylammonium bromide (AM). Removal of As was tested in batch studies in function of pH, adsorbent dosage, contact time, and initial arsenic concentration. The adsorption isotherms obey Langmuir mathematical model. Adsorption kinetics complies with pseudo-second-order kinetic model, and the constant rates were defined as 2.07 × 10−3and 0.92 × 10−3 g mg−1 min−1 for the samples (A) and (AM), respectively. The difference was caused by significant decrease in adsorption rate in initial state of the process carried out for the sample AM. The maximum adsorption capacity achieved for (A) and (AM) akaganeite taken from Langmuir isotherm was 148.7 and 170.9 mg g−1, respectively. The results suggest that iron oxides-hydroxides can be used for As removal from aqueous solutions.
Highlights
Arsenic is one of the most hazardous pollutants in many regions of the world as it can be solubilized in groundwater (Giri and Patel 2011)
Two types of adsorbents were obtained: (A) akaganeite and (AM) akaganeite modified with hexadecyltrimethylammonium bromide (HDTMA)
Substantial differences can be observed in the specific surface areas of both samples. They are, respectively, 254.0 (A) and 26.0 m2 g (AM). Such a ten-fold difference may indicate that the HDTMA filled up the pores of the akaganeite; the modification might occur
Summary
Arsenic is one of the most hazardous pollutants in many regions of the world as it can be solubilized in groundwater (Giri and Patel 2011). It has been reported that the arsenic poisoning causes melanosis; edema; keratosis; dark spots on the chest; enlargement of liver, kidney, and spleen; and cancers of skin, lungs, and urinary bladder (Giri et al 2011; Wang and Mulligan 2008; Choong et al 2007). For this reason, the World Health Organization (WHO) has recommended the maximum concentration of arsenic in drinking water as 10 μg L−1 & Based on the IPD kinetic model, it can be stated that the thickness of the theoretical boundary layer is smaller in the case of the modified mineral; the diffusion is enhanced.
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