Abstract
Mg/Al-NO_3 Layered Double Hydroxide(LDH) has been studied as an arsenic adsorbent. However, the adsorption performance of As(III) is low. For As(V), the adsorption rate by Mg/Al-NO_3 LDH was the highest (77.4%) at pH 3 and the lowest (56.9%) at pH 8. On the other hand, in regards to As(III), the adsorption rate of arsenic was the lowest at pH3 and the highest (40.2%) at pH8. Hence, we know that regardless of the pH value, Mg/Al-NO_3 LDH has higher adsorption performance for As(V) compared to As(III). In this study, Mg/Al-NO_3 LDH and ultrasound oxidation were used to improve the adsorption performance of arsenic. In this experiment, by using ultrasound oxidation, within As(III) solution (76.2 ppm) was prepared and ultrasound was irradiated into the solution for 2 hour. 38.7 ppm of As(III) was oxidized to As(V). When using Mg/Al-NO_3 LDH under ultrasound oxidation for 76 ppm of As(III) solution, we found that after adsorption experiment of the solution, almost all of As(V) was adsorbed. Moreover, adsorbed amount (35.2 ppm) of arsenic from the solution using Mg/Al-NO_3 LDH under ultrasound irradiation is almost same amount of oxidized (38.7 ppm) from As(III) to As(V) by ultrasound oxidation (previous experiment). Therefore, we believe that adsorbed arsenic consists almost entirely of As(V). We concluded that Mg/Al-NO_3 LDH can work as an arsenic adsorbent at pH3 for As(V). Thus we planned to use the ultrasound not only oxidation of As(III) but also pH adjustment using HNO_3 and HNO_2 generated.
