The spent pickling solution, which comes from the pickling process of iron and steel, is indispensable in the manufacturing industry. Iron gets dissolved in the acid solution during the pickling process. When the concentration of metal ions in the acid solution accumulates to a certain value, it cannot to be used to wash iron and steel materials and becomes spent pickling solution that should be treated before discharge. At present, spent pickling solutions are treated via neutralization precipitation techniques in industries. This treatment method has a large discharge of wastewater, and the cost is high due to which it cannot meet the needs of green cycle in industry production. In this study, a new method, which is based on the formation of quaternary ammonium salt precipitate in a strong acid solution, is proposed to treat the spent pickling solution. The spent pickling solution was recycled and reused by precipitation separation of iron ion. The quaternary ammonium salt was recycled by dissolving the obtained precipitate in an alkali solution. The new ferric hydroxide precipitate formed and quaternary ammonium salt was returned to the solution. In the whole process, only a few amount of alkali was consumed. The removal rate of iron ion was up to 99.72%. Compared with the traditional neutralization precipitation method, the acid is not consumed and it can be reused; the alkali was consumed only for the precipitation of iron ions, not for the neutralization of the acid. The proposed method is an effective and economic method for the recovery of the spent pickling solution. It is expected to satisfy the requirements of green cycle and environmental protection in industry production.

中文翻译：

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铁表面清洁酸洗溶液的清洁和环保再生

来自钢铁酸洗工艺的废酸洗解决方案在制造业中必不可少。在酸洗过程中，铁溶解在酸性溶液中。当酸溶液中的金属离子浓度累积到一定值时，就不能用于洗涤钢铁材料，而成为废酸洗液，应在排放前进行处理。目前，废酸洗液通过工业中和沉淀技术。该处理方法废水排放量大，成本高，不能满足工业生产中绿色循环的需要。在这项研究中，提出了一种基于在强酸溶液中形成季铵盐沉淀物的新方法来处理废酸洗溶液。将废酸洗溶液再循环并通过沉淀分离铁离子再利用。通过将获得的沉淀物溶解在碱溶液中来再循环季铵盐。形成新的氢氧化铁沉淀，并将季铵盐返回溶液。在整个过程中，仅消耗了少量的碱。铁离子的去除率高达99.72％。与传统的中和沉淀法相比，不消耗酸，可以重复利用。碱仅被消耗用于沉淀铁离子，而不被中和酸。所提出的方法是用于回收废酸洗溶液的有效且经济的方法。有望满足工业生产中绿色循环和环境保护的要求。