Combined process (oxidation/adsorption) for arsenic removal applying the UV/H2O2 process

LESCANO, M.; ZALAZAR, C. S.; CASSANO, A. E.; BRANDI, R. J.

Jacksonville, Florida

Congreso; AOTs-18: Advanced Oxidation Technologies for Treatment of Water, Air and Soil; 2012

Arsenic contamination is a serious public health problem in many countries. Contaminated groundwater by arsenic can have severe human health implications including various forms of cancer. Arsenic is released from soil into aquatic environment through natural processes and anthropogenic activities [1]. Due to the high toxicity of this metalloid, the World Health Organization (WHO) has set a maximum limiting guideline of 10ìg/L as the drinking water standard. Groundwater contains essentially only inorganic forms of As (III) and As (V). Trivalent arsenite is more toxic than pentavalent arsenic. Most technologies, commonly used for arsenic removal from water, require pre-oxidation of As (III) to As (V) to enhance the removal of As (III) due to the fact that As (V) adsorbs more strongly onto solid phase adsorbents than As (III). In a previous study it has been shown that a combination of hydrogen peroxide and UVC radiation is an effective and feasible process to oxidize arsenic in water [2]. Therefore it is interesting to study, as a next step, the removal of As (V) and the design of a combined oxidation/adsorption equipment. According to the different existing technologies, adsorption is an attractive method because it seems to be efficient, economic and relatively simple to carry out. Thus, three adsorbentes (Activated Alumina, Titanium Dioxide and Granular Ferric Hidroxide) were tested, being the last two mentionted the most efficient materials for As (V) removal. The main objective of this research is to design a combined equipment which includes a photochemical reactor for the oxidation (process previously studied) connected to an adsorption column filled with the selected.adsorbents. A discontinuous anular photochemical reactor was built with one 40 W tubular germicidal lamp (ë = 253.7 nm). At the outlet of the reactor, part of the solution was recirculated to the same reactor while the other portion was forced to let into the adsorption column. The whole system was operated in a continuous mode. Experiments were performed by varying the concentration ratio of As (V) / As (III) (75/125, 50/150, 25/175) at the same total arsenic concentration (200 ìg/L of As (III)). The H2O2 concentration employed was 6 mg/L. Experimental results have shown that with a flow rate of 0.8 mL/min a concentration of As (III) less than 2 ìg/L after the reaction (UV/H2O2 process) is achieved Also, a complete removal of the contaminant to the output of the adsorption column is obtained. Therefore, it can be concluded that the combined technology (oxidation-adsorption) is feasible and promising for arsenic removal in water to small and medium scale.