Abstract

In this research, iron/copper bimetallic nanoparticles were used to remove arsenic from aqueous solutions as well as its immobilization in soil matrix. Nanoparticles were synthesized using two different protocols, resulting in two different sizes of particles and the physicochemical characterization was determined using XRD, TEM, BET and XPS techniques. To apply the nanoparticles in a soil environment, nanoparticles were stabilized with various starch concentrations. Characterization of nanoparticles resulting from the two methods of synthesis indicated that the mean diameter of nanoparticles were 13.17 nm and 27.15 nm. For both nanoparticles, adsorption isotherms fit well with the Langmuir equation and the maximum sorption capacities for As(III) and As(V) were 19.68 mg/g, and 21.32 mg/g respectively at pH 7.0 for the first nanoparticle size and 5.55 mg/g and 10.41 mg/g for As(III) and As(V) respectively for the second nanoparticle size. The kinetic test revealed that sorption follows pseudo-second-order and coexisting HCO3-, SO42- , and PO43- had an insignificant influence on arsenic adsorption at equal initial concentrations to As. Based on transport studies, for immobilization of arsenic in contaminated soil, 0.04 wt.% starch stabilized Fe/Cu nanoparticles were used. For this nanoparticle, the Langmuir adsorption isotherm was fitted and showed the maximum sorption capacity of 90.1 mg/g, and 126.58 mg/g for As(III) and As(V) respectively. Soil column breakthrough tests and elution profiles proved the mobility of the starch stabilized nanoparticles when 15% of the nanoparticles were retained in the soil bed. Starch stabilized Fe/Cu nanoparticles were highly effective for arsenic immobilizing in the contaminated soil. When the soil was treated in batch experiments with nanoparticles (0.4 g/L) at a soil to liquid ratio of 0.1, the water leachable arsenic was reduced from 55 µg/L to 4.23 µg/L. Column elution tests indicated that application of a starch stabilized Fe/Cu suspension transferred nearly all water-soluble arsenic to nanoparticle phase. Then arsenic can become immobilized in the soil bed as the nanoparticles are immobilized in the soil matrix. The results of this research can lead to introducing an effective and efficient alternative adsorbent for removal of arsenic from water and its stabilization in contaminated soils.