Preparation Of ?-FeOOH Catalyst And Performance Of Fe²⁺ Removal By Autocatalytic Reaction

Fenton oxidation method is one of the most widely used in advanced oxidation technology, it has many advantages such as a wide range of applications, mild reaction conditions, and equipment is simple. However, Fenton process effluent contains a lot of Fe2+ ions, the removal of iron ions commonly used alkaline agent to form precipitation,which is likely to cause secondary pollution. Therefore, it is particularly important to find a method to remove Fe2+ ions of Fenton effluent.In this paper, a y-iron-based hydroxide catalyst was developed. The Fe2+ ion removal ability of water was studied by using the self-catalyzed crystallization of the catalyst. The aim of the experiment was to solve the problem of Fe2+ ion removal in Fenton process. At the same time, reduce the secondary pollution caused by using reagents on the environment,and reduce the cost of ferrous ion treatment.In the preparation of y-FeOOH catalyst, the main reagent was NaOH and FeSO4, The equivalence ratio R of NaOH and FeSO4 directly affects the purity of ?-FeOOH. When R was 0.85, its purity was the highest, reaching 64.3%. Adding proper amount of disodium hydrogen phosphate can improve the purity of ?-FeOOH and change its crystal morphology.The purity of ?-FeOOH can reached 90.8% when 1% Na2O equivalent of phosphate was added.The effects of phosphate addition on the preparation of the catalyst were investigated.Phosphate was added in the preparation process at the equivalent concentrations of 0.2%,0.5%, 1%, 2% and 8% Na2O, respectively. The catalyst prepared by adding 0.2% Na2O equivalent of phosphate has components of ?-FeOOH and a-FeOOH. The catalysts prepared with 0.5%, 1%, 2%, and 8% Na2O equivalent phosphates all contain only?-FeOOH. When the amount of phosphate added is increased, the time required for the reaction to reach FeOOH-forming conditions is increased.According to the SEM images of the catalyst obtained, the amount of ?-FeOOH formed was gradually changed from needle type to sheet form. The catalyst prepared by adding 0.2% Na2O equivalent phosphate to the needle form; the catalyst prepared by adding 1% Na2O equivalent phosphate, the crystal form of the catalyst is uniform; the catalyst prepared by the addition of 8% Na2O equivalent of phosphate gave a crystalline form that tended to be non-homogeneous.The removal of iron was carried out using a catalyst prepared by adding different doses of phosphate. The mass of 1 g ?-FeOOH was added into the water containing 4.09 mg/L Fee+, then oxygen was added and the reaction was stirred for 24 h. ?-FeOOH which prepared by adding 1% Na2O equivalent of phosphate had the best removal efficiency, with the removal rate of 78.32%. Vermiculite-Fenton reaction solution pH adjusted to 7.0, then add the quality of 1g of ?-FeOOH (y-FeOOH prepared by adding 1% Na2O equivalent of phosphate), the reaction was carried out under oxygen for 24 h. ?-FeOOH can remove the iron effectively, and the removal rate is up to 97.48%. The catalyst used in the iron removal experiment was measured by XRD. The results of X-ray diffraction (XRD) show that the composition of the catalyst was ?-FeOOH, which was consistent with the mechanism of?-FeOOH removal from Fe2+.