RESUMO
Adsorption is a technology used to remove arsenic from water contaminated at levels above drinking water standards. In this study, New Zealand Iron-Sand (NZIS), a naturally-available adsorbent was investigated for its efficiency in removing both As (III) and As (V). Several batch tests were conducted with different concentrations of arsenic at different pH conditions. During the batch tests, the maximum adsorption of As (III) occurred at a pH of 7.5, while As (V) adsorption reached its maximum value at a pH of 3. Both Langmuir and Freundlich adsorption models were found to fit with R(2) values greater than 0.92. From the Langmuir adsorption model, the maximum adsorption capacity of NZIS for As (III) and As (V) were estimated to be 1,250 and 500 µg/g, respectively. These values were substantial enough to consider NZIS a promising new adsorbent for arsenic removal.
Assuntos
Arsênio/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Concentração de Íons de Hidrogênio , Ferro/química , Modelos Químicos , Dióxido de Silício/químicaRESUMO
A lab-scale sequencing batch reactor (SBR) was operated at a solids retention time (SRT) of 20 +/- 2.5 days to develop a consortium of denitrifying bacteria with a mean specific denitrification rate of 0.11 g nitrate (NO(3)(-)-N)/g volatile suspended solids (VSS)/day. This biomass was used in a series of denitrification batch tests which used volatile fatty acids (VFAs) as their external carbon source. The VFAs were generated from an anaerobic digester that had an effluent VFA concentration of 5655 +/- 876 mg/L (expressed as acetic acid (HAc)). The denitrification batch reactors were spiked with NO(3)(-)-N (carbon-to-nitrogen (C:N) ratio of 3.0) and different concentrations of arsenite (a trivalent arsenic salt) in order to quantify the effect of arsenite on the denitrification process. A steady deterioration in the ability of the biomass to denitrify under increasing arsenite concentrations was observed with the mean specific denitrification rate dropping from 0.183 g NO(3)(-)-N/gVSS/day at an arsenite concentration of 5 mg/L, to a value of 0.047 g NO(3)(-)-N/gVSS/day at a concentration of 25 mg/L.