Removal of arsenic from groundwater by granular titanium dioxide adsorbent

A novel granular titanium dioxide (TiO2) was evaluated for the removal of arsenic from groundwater. Laboratory experiments were carried out to investigate the adsorption capacity of the adsorbent and the effect of anions on arsenic removal. Batch experimental results showed that more arsenate [As(V)] was adsorbed on TiO2 than arsenite [As(III)] in US groundwater at pH 7.0. The adsorption capacities for As(V) and As(III) were 41.4 and 32.4 mg g−1 TiO2, respectively. However, the adsorbent had a similar adsorption capacity for As(V) and As(III) (approximately 40 mg g−1) when simulated Bangladesh groundwater was used. Silica (20 mg l−1) and phosphate (5.8 mg l−1) had no obvious effect on the removal of As(V) and As(III) by TiO2 at neutral pH. Point-of-entry (POE) filters containing 3 l of the granular adsorbent were tested for the removal of arsenic from groundwater in central New Jersey, USA. Groundwater was continuously passed through the filters at an empty bed contact time (EBCT) of 3 min. Approximately 45 000 bed volumes of groundwater containing an average of 39 μg l−1 of As(V) was treated by the POE filter before the effluent arsenic concentration increased to 10 μg l−1. The total treated water volumes per weight of adsorbent were about 60 000 l per 1 kg of adsorbent. The field filtration results demonstrated that the granular TiO2 adsorbent was very effective for the removal of arsenic in groundwater.