| Many mineral processing industries located at the region of Ganxi river, lackingeffective management of tailings caused tailings deposited in the river. HunanRecearch Academy of Environmental Sciences employed smelting and dressingprocess to conducted the comprehensive utilization of river channel tailings,whichwas an important component of The grand national science-technology project. Theprocess generated the dressing wastewater(contained varieties of heavy metals) andthe smelting wastewater(contained high concentrations of arsenic). Compared withthe conventional mineral smelting and industrial wastewater, their treatments are moredifficult without mature feasible processing technologies. My paper mainly studiedthe treatment technologies of dressing wastewater and smelting wastewater. On thebasis of optimization of the preparation condition of inorganic-organic compoundflocculant, conducted the laboratory experiment and expanded experiment on thetreatment of backfilling smelting wastewater, as well as the laboratory experiment andpilot experiment on the treatment of backfilling dressing waste water. The mainresults were as follows:(1) The studies found that the compound flocculant prepared by polymeric ferricsilicate and dimethyldiallylammonium chloride had a good removal capacity forheavy metals and COD in the waste water; The optimal preparation conditions of thecompound flocculant: silicate activated pH=2-3, activated time was6h, iron siliconratio was2.5:1, modifiers dosage was0.25g/100mL, modification time was15min,modification temperature was80°C. Characterization results of SEM, FTIR and XRDshowed that the crystal structure, chemical properties and morphologicalcharacteristics of the compound flocculant are changed dramatically; The compoundflocculant is not a simple physical mixture, but a new compound.(2) Results of combined process of sodium sulphide and compound flocculantfor treatment of backfilling smelting wastewater showed that on the condition ofsodium sulphide additive quantity was5.5g/100ml (dosing in two sections: pH ofeach section was controlled at2.0, dosing quantity3.5g/100ml and2.0g/100ml,respectively) and reaction time was5min, the arsenic removal efficiency couldreached as high as99.96%. After that, compound flocculant was used forsedimentation treatment of the smelting wastewater; On the condition of compound flocculant dosage was7ml/L, pH=8, the concentration of arsenic remained in thetreated water was lower than0.4mg/L. Results of expanded experiment showed thatarsenic removal rate was above99.9%by the vulcanization. Results of XRD, XRFcharacterization conducted on the arsenic slag produced by vulcanization process,demonstrated that the arsenic and sulfur content was49.15%and40.98%,respectively and the impurity content was lower than10%, so the arsenic slag can beused as raw material for the production of arsenic trioxide and elemental sulfur.(3) Results of treatment for dressing wastewater using the compound flocculantshowed that: on the condition of compound flocculant dosage7ml/L, initial pH ofwastewater was8.0, settling time was4min, stirring speed was120-160r/min,stirring time was20-30s, and reaction temperature was15-35°C, removal rate of As,Cd, Zn, Pb, COD and turbidity in wastewater after treated, could reach to97.2%,97.2%,99.4%,99.6%,92.1%,99.6%, respectively. Flocculation settling time was5min and the sludge volume ratio was0.054(sedimentation time without flocculantwas90min and settling sludge volume ratio was0.093).(4) Pilot results of treatment for dressing wastewater using the compoundflocculant showed that: the concentration of Cd, As, Zn, Pb, COD and turbidity intreated effluent was was lower than50μg/L,50μg/L,40μg/L,40μg/L,30mg/L,20NUT, respectively. Indexes obtained from reusing the treated water were almost thesame with that using the fresh water. Wastewater treatment and reuse system couldproduce high environmental and economic benefits. |
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