Arsenic removal from water employing UV radiation and granular titanium dioxide: bath experiences

M.R. LESCANO; C.S. ZALAZAR; BRANDI, R.J.

Conferencia; The 20th International Conference on Advanced Oxidation Technologies for Water, Air and Soil Remediation (AOTs-20); 2014

Arsenic pollution is a worldwide problem being one of the most important environmental issues in last years and has been extensively reported by literature.Arsenic in water usually occurs in its two inorganic forms, As (III) and As (V) depending on the prevalent redox conditions, being As (III) more toxic in biological systems than As (V). There are many technologies to oxidize arsenic in water either by traditional oxidants such as Cl2, ClNH2, ClO2, H2O2, KMnO4 or advanced oxidation technologies (AOTs) such as UV /TiO2, UV/H2O2, UV/Fe (III)/H2O2. The AOTs are more convenient for arsenic oxidation in water because they do not generate undesirable or by-products. In a previous work the efficiency and kinetics of the UV/H2O2 process for arsenic oxidation was studied. Then, the adsorption process was studied because of its simple operation and relative low cost for arsenic removal.The results showed that the granular titanium dioxide is a good adsorbent for arsenic removal (paper Lescano). Also, titanium dioxide is well-known for its photocatalytic activity (papers).The main objective of the present work is to design experiments in order to evaluate and study the effectiveness of the combination of UV/TiO2 process for As removal employing a commercial granular titanium dioxide. Arsenic removal will be produced through the: oxidation of As (III) by UV/TiO2 and its subsequent adsorption onto titanium dioxide. The aim of the work is can also study both phenomena separately (oxidation and As (V)/As(III) adsorption).The employed commercial TiO2 was characterized employed different techniques (DRX, XPS, Raman, IR). The experiences were carried out in a batch system at room temperature using a similar system as a Jar Test with 7 beakers (500 mL), but employing a germicidal UVC lamp (ʎ= 254 nm) placed at the top of the entire system. Solutions with different As (III) concentration ranging from 25 to 200 µg L-1 were prepared by dilution of the stock solutions and different weight of adsorbent were added to each beaker at three levels: 0.1 g/L, 0.01 g/L and 0.001 g/L. The mixing speed was set at 140 rpm. Preliminary results show that the granular titanium dioxide has good activity for photocatalysis for all the suspensions tested and that is possible to isolate oxidation from adsorption in the entire system. The results are in accordance with the information obtained from the different techniques that shown a 80% of anatase. This study enables to carry out both operations in a compact equipment (for example a fixed bed photoreactor for arsenic removal).