Preparation Of MgAlFe And NiFe Hydrotalcite-like Compounds And Its Catalytic Degradation Of Malachite Green

The pollution of water resources due to the indiscriminate disposal of numerous inorganic and organic contaminants from industries and human life has been causing worldwide concern in recent years. Printing and dyeing wastewater containing refractory dyes is one of research hotspots in the field of water treatment. As one of advanced oxidation processes?AOPs?, heterogeneous Fenton-like method has certain advantages and is a better wastewater treatment method.The objective of this research is to degrade organic dyes in simulated waste water by hydrotalcite-like catalysts catalyzing H₂O₂ and producing hydroxyl radicals.MgAlFe-HTLCs and calcined NiFe-HTLCs heterogeneous catalysts are synthesized through solid phase reaction and modified urea method, respectively. A series of catalytic reactions have been conducted to degrade malachite green?MG? for MgAlFe-HTLCs and calcined NiFe-HTLCs. The influences of initial pH, dosage of catalyst, reaction time, optimum dosage of H₂O₂ and initial dye concentration on degradation were also researched. Moreover, the durability of catalysts and reaction mechanisms are also investigated. The following conclusions were acquired:?1? MgAlFe-HTLCs was prepared by solid phase reaction at room temperature and modified via a hydrothermal process and characterized by XRD, SEM, BET,FT-IR, and TG/DTA. The experimental results showed that MgAlFe-HTLCs had good layered structure in the condition of same proportion of iron and aluminum, 18 h of crystallization time and 110? of crystallization temperature. To evaluate the degradation effect, the influences of various parameters such as initial pH, dosage of catalyst, optimum dosage of H₂O₂ and initial dye concentration on degradation were also researched. Under the conditions of 0.1 g�L^-1 MgAlFe-HTLCs, 1 mL H₂O₂ and natural pH of 6.3, almost up to 99.0% degradation rate of 10 mg�L^-1 malachite green?MG? solution was achieved within 30 min. Except for that, total organic carbon?TOC? removal reached 38.9% during 30 min, while 72.2% of TOC removal wasachieved in 70 min. For used catalyst, XRD, BET and EDS were measured to further discuss the stability and durability. The results of reusability test showed no obvious loss in the catalytic activity after three consecutive experimental runs.?2? NiFe-HTLCs was synthesized by the modified urea method. The structure,morphology and particle size of the products were characterized by XRD, SEM,FT-IR, TG/DTA, BET and EDS. The results showed that NiFe-HTLCs compounds had good layered structure when the crystallization temperature is 110?,crystallization time at 24 h, initial pH is adjusted to 3, and the molar ratio of Ni and Fe is 3:1. Calcined NiFe-HTLCs was obtained by calcining at 500?, and the specific surface area of the catalyst was greatly increased by 55%, which was beneficial to the catalytic degradation. In the condition of calcined NiFe-HTLCs of 1 g�L^-1, H₂O₂ of300 mM and natural pH of 6.3, the adsorption and degradation of Malachite Green?MG? solution of 10 mg�L^-1 were carried out. The decolorization rate was 60% after the adsorption of 5 h. After adding hydrogen peroxide, the decolorization rate of 99%was acquired during the reaction time of 60 min.