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Regeneration of spent alkali from aluminum washing

机译：铝洗回收废碱

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Spent liquor from washing of aluminum section materials after etching with caustic soda (NaOH) has been treated.Aluminum was removed from the liquor and caustic soda was regenerated by:(a) adding precipitating agents to hydrolyze sodium aluminate (Na_2AlO_2),(b) separating the aluminum precipitate,and (c) concentrating free NaOH in the resulting solution which is reused in the etching process.Four systems were investigated:hydrated lime {Ca(OH)_2},hydrogen peroxide (H_2O_2),H_2O_2/Ca(OH)_2 mixture,and dry lime (CaO).Different parameters,such as additives concentration,time and temperature were investigated.Results obtained revealed that CaO was more efficient in the removal of aluminum from the spent liquor with higher hydrolyzing rate of Na_2AlO_2 than Ca(OH)_2,H_2O_2,or their mixture.The removal efficiency value of aluminum was 96.1% with 100 g/L of CaO at 60 deg C after 30 min treatment,while the efficiency values were 83.2 and 90.1% with Ca(OH)_2 and H_2O_2,respectively after 2h treatment.The presence of Ca(OH)_2 in the H_2O_2/Ca(OH)_2 mixture has no great effect on the Al removing efficiency comparing to that using H_2O_2 alone,however,it greatly facilitated the separation of the Al precipitate from the solution as calcium aluminate hydrate.Caustic soda concentration of 102 g/L,which is applicable for reusing as etching solution,was obtained by heating the solution for 1 h at 95 deg C.
机译：用苛性钠（NaOH）蚀刻后洗去铝型材的废液已得到处理。从液中除去铝并通过以下方法再生苛性钠：（a）添加沉淀剂以水解铝酸钠（Na_2AlO_2），（b）分离铝沉淀物，并（c）在所得溶液中浓缩游离的NaOH，以在蚀刻过程中重复使用。研究了四个系统：熟石灰{Ca（OH）_2}，过氧化氢（H_2O_2），H_2O_2 / Ca（OH） ）_2混合物和干石灰（CaO）。研究了添加剂浓度，时间和温度等不同参数。结果表明，与Na2O2相比，CaO对Na_2AlO_2的水解速率更高，可以有效地从废液中去除铝。 （OH）_2，H_2O_2或它们的混合物。处理30分钟后，在60摄氏度下100 g / L CaO对铝的去除效率值为96.1％，而Ca（OH）对铝的去除效率值为83.2和90.1％分别在2h tr后_2和H_2O_2与单独使用H_2O_2相比，H_2O_2 / Ca（OH）_2混合物中Ca（OH）_2的存在对Al的去除效率没有很大的影响，但是，它极大地促进了Al沉淀物从溶液中的分离。通过将溶液在95℃下加热1 h，可得到102 g / L的苛性钠浓度，可重新用作蚀刻液。

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