| The pickling process of steel materials is indispensable in the manufacturing industry.During the pickling process,due to the dissolution of metal ions,the concentration of metal ions continuously increases.When the concentration of metal ions accumulates to a certain value,the acid used for cleaning will fail.The waste solutions cannot be discharged because they contain a large amount of acidic and metal ions.At present,the most commonly used method of treating acidic waste liquids is neutralization,with limestone as a neutralizing agent.However,there are some disadvantages such as large amount of pollutants discharged,difficult sludge treatment.Therefore,it is of great practical significance to explore a green recycling for recovering pickling solution.In this paper,the quaternary ammonium salt precipitation recovery treatment process is proposed.The principle is that the quaternary ammonium salt can react with FeCl4-to form a precipitate in the strongly acidic solution.First to the Fe ions to FeCl4-ions,then the quaternary ammonium salt is added.After a simple precipitation and separation process,Fe is separated from the pickling solution to realize the reuse of the acid.The precipitate is transformed into chemical reagent iron oxide by high temperature calcinations.This paper mainly carried out the following work:(1)Study on Removal of Fe3+ by Quaternary Ammonium Salt in Acidic Waste SolutionUsing the properties that iron ions complex with chloride ions to form anions,sodium chloride is first added to the acidic solution,and the iron ions will become iron tetrachloride anions,and then quaternary ammonium salt are added to form insoluble acid precipitates.The effects of the quaternary ammonium salt type,tetrabutylammonium chloride addition amount,reaction time,hydrochloric acid concentration,chloride ion concentration,and hydrogen ion concentration were examined.Recyclable performance test results show that Fe ion concentration is less than 0.1g dm-3.(2)The Mechanism of Quaternary Ammonium Salt PrecipitationBy means of the EDS elemental analysis,the XRD,the infrared spectroscopy and other characterization methods,Proving that the precipitation product of the quaternary ammonium salt precipitation method was C16H36NFeCl4,and no new elements were introduced during precipitation formation process.The precipitation was caused by the combination of tetrabutylammonium chloride and FeCl4-.The precipitation did not interact with the functional group,thereby the structural formula of precipitated C16H36NFeCl4 was introduced.The precipitate is not a simple mixture of tetrabutylammonium chloride and FeCl3 but a new substance.The experimental design idea was verified.(3)Quaternary ammonium salt precipitation method for recovery of iron-containing waste acidsBased on the determination of the quaternary ammonium salt precipitation,the effects of quaternary ammonium salt precipitation method treating the Fe3+ simulated pickling solution containing different concentrations of hydrochloric acid,the sulfuric acid,the nitric acid,the phosphoric acid,the citric acid and the mixed acids were investigated.And the effects of this method treating the Fe2+ simulated pickling solution containing different concentrations of hydrochloric acid,sulfuric acid,nitric acid and phosphoric acid and the amount of addition of hydrogen peroxide were also explored.The results of the study show that the quaternary ammonium salt precipitation method can treat different types of acidic waste liquid containing iron. |
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