廃水中のAsの金属水酸化物共沈法による除去に関する研究
1980 年 96 巻 1107 号 p. 325-329
詳細
1980 年 96 巻 1107 号 p. 325-329
The removal of arsenic from waste water has been investigated by means of coprecipitation with aluminum hydroxide or ferric hydroxide. Artificial waste solutions cotaining 10mg/l of As (III) or As (V) were used as experimental solutions.
The results obtained were as follows:
1) By the coexistence of 200mg/l of aluminum ion, As (III), was scarecely removed at all pH range, whereas As (V) was lowered to about 2mg/l at pH range between 5 and 8. The removal of As (V) may be attributed to the adsorption of As (V) anionic species on the surface of aluminum hydroxide.
2) When ferric ion was added to the waste water, As (V) was effectively removed over wide pH range, even though the addition of ferric ion was low. The settling characteristics of ferric hydroxide coprecipitated with arsenic were rather poor, meanwhile the arsenic concentration of supernatant solution after settling the precipitate for 3 hours was remarkably higher than that of the filtrate. In order to reduce the concentration of As (III) to meet the effluent standard (0.5mg/l) by settling the precipitate for 1 or 3 hours, it was necessary to add ferric ions in the weight ratio of more than 20 or 10, respectively, against arsenic involved. The concentration of As (III) in the filtrate, however, could be reduced to 0.5mg/l by adding ferric ions in the weight ratio of 3 against arsenic involved. While, in the case of As (V), the addition of ferric ions in the weight ratio of more than 10 or 5 against arsenic involved was sufficient for reducing the concentration of arsenic to 0.5mg/l by settling the precipitate for 1 or 3 hours, respectively. Also, the concentration of As (V) in the filtrate was reduced to 0.5mg/l when ferric ion was added in the weight ratio of 0.75 against arsenic involved.
3) The removal of As (V), which was obtained in the presence of ferric ions in a limited acidic pH range, may be due to the formation of ferric arsenate, while the removal of As (V) in a higher pH range could be explained by the specific adsorption of As (V) anionic species on the surface of ferric hydroxide. On the other hand, As (III) is considered to be removed only by the specific adsorption of As (III) anionic species on the surface of ferric hydroxide.
