Arsenic Removal Technology from Water Based on Nanomaterials and Sunlight
Abstract
A new technology for arsenic (As) removal has been addressed by the design and construction of a treatment prototype equipment called "SolArsenic". This prototype is mainly composed of a solar collector as a photo-reactor and the use of a bi-functional material based on a semiconductor (Titanium Dioxide-TiO2) and an adsorbent (Activated Carbon-CA). The prototype achieves the photo-oxidation of As (III) to As (V) and the progressive adsorption of As (V), by means of one-step reaction system and using simulated solar light as source of radiation. A specific semiconductor (TiO2-4) with the best properties for photo-oxidation of As (III) in the presence of simulated solar light, and an activated carbon chemically modified with iron (CA-Fe) , which presents the best properties for the efficient adsorption of As (V), were selected as components of the bi-functional material. Preliminary results about the optimal proportions of the materials (TiO2: CA-Fe), the best material loads and the influence of the proportion of UV-Visible light were evaluated in a laboratory scale by using a small-scale photo-reactor (solar simulator) and 200ml of solution of As (III) (1000 and 5000 ppb). For the removal of As on a prototype scale, the efficiency was evaluated for synthetic water contaminated with different concentrations of As (III) (1000 and 5000 ppb) and for different of pH-values (4, 7, 9). Results shows a high removal efficiency (> 90% in all the studied pH), which involves the photo-oxidation of As (III) in 30-60 minutes and the progressive adsorption of As (V), reaching water quality standards (irrigation norm, NCh 1333 and drinking water, WHO). The removal capacity of the material shows to be dependent on water pH-values.