Precipitation Removal of Sulfite Ions from Waste Developing Solution by the Addition of Calcium Salt.

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  • カルシウム塩添加による写真現像廃液からの亜硫酸イオンの沈殿除去
  • カルシウムエン テンカ ニ ヨル シャシン ゲンゾウ ハイエキ カラ ノ アリュウサン イオン ノ チンデン ジョキョ

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Abstract

Photographic developing solution is a mixed solution containing some organic substances of developing agents and a large amount of sodium sulfite, i.e., an antioxidant of the organic substances. Therefore, the wastewater of developer displays a high COD value. The treatment of the contained organic substances such as metol (p-methylaminophenol sulfate) and hydroquinone (p-dihydroxy-benzene) are hardly oxidized or decomposed because of the large amount of sulfite ions which exist.<BR>In this research, removal of the sulfite ions from waste developers with calcium ions was first examined to precipitate sulfite ions as calcium sulfite and reduce COD value. The optimum conditions for this reaction were examined. Oxidation of the organic substances with hydrogen peroxide was also examined to reduce the COD value in the solution after the separation.<BR>The following results were obtained as experimental results. Most of the sulfite ions in the solution were instantaneously removed by the addition of calcium chloride as a precipitate of calcium sulfite hemihydrate. Addition molar ratio of calcium to sulfite ions was found to be 1.5 at pH 8 for the removal sulfite ions of about 100%. The crystalline and the size of the precipitate were desirable for separation of the precipitates from the solution. By using hydrogen peroxide, the oxidation and decomposition of metol and hydroquinone was performed, then COD value of 80-90% of the initial waste solution was decreased.

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