Abstract
Arsenic (As) contamination of water is a serious problem in developing countries. In water streams, arsenic can be as As(V) and As(III), the latter being the most toxic species. In this work, an innovative adsorbent based on CaTiO3 nanoparticles (CTO) was prepared by the sol-gel technique for the removal of As(III) from aqueous solution. X-ray diffraction of the CTO nanoparticles powders confirmed the CTO phase. Transmission electron microscopy observations indicated an average particle size of 27 nm, while energy dispersive X-ray spectroscopy analysis showed the presence of Ca, Ti, and O in the expected stoichiometric amounts. The surface specific area measured by Brunauer, Emmett, and Teller (BET) isotherm was 43.9 m2/g, whereas the isoelectric point determined by Zeta Potential measurements was at pH 3.5. Batch adsorption experiments were used to study the effect of pH on the equilibrium adsorption of As(III), using an arsenite solution with 15 mg/L as initial concentration. The highest removal was achieved at pH 3, reaching an efficiency of up to 73%, determined by X-ray fluorescence from the residual As(III) in the solution. Time dependent adsorption experiments at different pHs exhibited a pseudo-second order kinetics with an equilibrium adsorption capacity of 11.12 mg/g at pH 3. Moreover, CTO nanoparticles were regenerated and evaluated for four cycles, decreasing their arsenic removal efficiency by 10% without affecting their chemical structure. X-ray photoelectron spectroscopy analysis of the CTO surface after removal experiments, showed that arsenic was present as As(III) and partially oxidized to As(V).
Highlights
Water is one of the fundamental factors for the development of humanity
It is estimated that between 60 and 100 million people in the world are exposed to the presence of As in drinking water, in concentrations harmful to health
The CaTiO3 nanoparticles (CTO) nanoparticles prepared by the sol-gel technique were demonstrated to be a good adsorbent of As(III) with a maximum adsorption capacity of 11.12 mg g−1 at room temperature, which is higher than other values reported in similar studies
Summary
Water is one of the fundamental factors for the development of humanity. The contamination of water sources with arsenic (As) is a serious worldwide problem. It is estimated that between 60 and 100 million people in the world are exposed to the presence of As in drinking water, in concentrations harmful to health. It has been reported that at least 21 countries have high concentrations of As in their groundwater [1,2]. The most affected areas in the world are South-East Asia, in countries such as Bangladesh, India, Nepal, Taiwan and Vietnam, where concentrations of As that exceed 1 mg/L have been reported [3]. The World Health Organization (WHO) sets as maximum permissible limit 10 μg/L of As in drinking water [4]
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