Research On Hydrothermal Sulfidation And Flotation Of Zinc-containing Sludge Based On The Regulation Of Mineralizer

As a major source of heavy metal pollution, it is great important to treat heavy metal residues safely. Moreover, the problem of depletion of mineral resources in China is becoming more serious. Heavy metal residues as a secondary mineral resources has become a major research topic in the environmental protection and non-ferrous industry. Hydrothermal sulfidation-flotationreceived wide attention because it can simultaneously achieve recycling and sound of heavy metal waste. However, the technology still have some problems to be solved, such as low grade flotation concentrate, grain tiny sulfide.The study was based on the shortcomings of the technology.In this study, the effect of mineralizer in the progress of hydrothermal sulfidation-flotation was investigated by studying simulated waste residue and real neutralization sludge to explore the practical application feasibility of the process. The main results are as follow:(1)The influence of the physical and chemical properties of simulated waste by mineralizer showed that NaCl, CH3COONa, EDTA-2Na promoted the ZnS grew up in the process of hydrothermal crystallization. Compared to without mineralizer, ZnS grain size increased from26.1nm to31.3nm,32.4nm,32.7nm respective.The surface area analysis of hydrothermal sulfidation product showed that sulfide product specific surface area decreased under the condition of adding these three kinds of mineralizer. The specific surface area of hydrothermal sulfidation product reduced from2.53m2/g to1.86m2/g with CH3COONa.Zeta potential analysis of the hydrothermal sulfidation product resulted that adding CH3COONa and EDTA-2Na can reduce ZnS surface negative charge in the range of pH8-10. SEM analysis showed that the crystal of ZnS become homogeneously. The reunion of ZnS and CaSO4can be weaken under the conditions of CH3COONa and EDTA-2Na. Thus, NaCl, CH3COONa and EDTA-2Na could change the physicochemical properties of the hydrothermall sulfidation product and significantly control ZnS crystal growth. (2)Mineralizer regulation on hydrothermal sulfidation-floatation of neutralization sludge shows,the optimal concentrationg of NaCl^CH3COONa and EDTA-2Na were0.1mol/L、0.5mol/L and0.1mol/L. Enrichment ratio of zinc increased from1.16to1.36,1.62and1.69respectively. XRD analysis and results of grain size calculation indicated that three types of mineralizer can improve the crystallization effect of the products of hydrothermal and promote ZnS crystal growth. Compared without mineralizer adding, ZnS grain size increased from21nm to35nm. TEM-EDS analysis of mineralizer regulation indicated that ZnS become from the floc particles into small dense bulk crystal, while reunited with CaSO4and ZnS crystals had be weakened.(3) Pilot test with the control of the mineralization indicated that Under the optimal situation of hydrothermal sulfidation, Zn enrichment ratio can reach1.6or more and the recovery can stabilize at80%.Economic engineering analysis showed that Process of fixed investment cost was1.69million yuan.and the variable costs was million yuan. According to this process, the profit can achieved300,000yuan with processing800tons waste per year. Investment in the process, five years can recover the cost of the process. Environmental benefits indicated that according to the heavy metal content of10%, the emissions of heavy metals in the optimal process can reduce by800tons of solid waste and recyce56tons of heavy metals each year. The optimal process can reduce the environmental pressure of heavy metal pollution and provide a guarantee the safety of residents by this process.