Treatment And Reuse Of Phosphate Rock Reverse Flotation Wastewater

Flotation process is the most widely used beneficiation process with simple operation and low cost.However,a large amount of wastewater will be produced in this process.The most appropriate way to treat wastewater is to reuse them.The beneficiation wastewater will produce a large number of organic and inorganic pollutants after repeated recycling,especially the accumulation of Ca²⁺and Mg²⁺ions,which will have an adverse impact on the flotation process.Therefore,it is necessary to treat the beneficiation return water.In this paper,"micro sand ballasted flocculation sedimentation"and"double alkali+polyacrylamide（PAM）"were used to treat the beneficiation wastewater of a phosphate concentrator in Hubei Province.The appropriate treatment process was determined,the cost of the two treatment processes was compared,and the effect of effluent reuse after treatment was evaluated.The conclusions of this paper are as follows:The thermodynamic analysis of the main chemical reactions in the treatment of phosphate rock reverse flotation wastewater by"micro sand ballasted flocculation sedimentation"and"double alkali+PAM"was carried out.The results showed that the Gibbs free energy of the two reactions was less than 0,and the reactions can be carried out spontaneously.The effects of pH value,particle size of zeolite powder,dosage of zeolite powder,dosage of PAM,hydraulic conditions and temperature on the treatment of phosphate rock reverse flotation wastewater by"micro sand ballasted flocculation sedimentation"were investigated through single factor test.Considering the removal efficiency of Ca²⁺and Mg²⁺ions and sludge settling performance,the suitable conditions of the process were determined.That is,5 g zeolite powder with particle size of 120～150 mesh was added at room temperature,adjusted the pH value of the wastewater to 9.5 with Na OH solution.After stirring for 5 minutes,6 m L of 3‰PAM solution was added,and the mixture was stirred quickly at 400 r/min for 40 s and then slowly at 70 r/min for 6 min.Under this condition,the total removal efficiency of Ca²⁺and Mg²⁺ions in wastewater can reach 96%.The effects of Cao dosage,Na₂CO₃ dosage,reaction time,PAM dosage,hydraulic conditions and temperature on the treatment of phosphate rock reverse flotation wastewater by"double alkali+PAM"were investigated through single factor test.Based on the removal efficiency of Ca²⁺and Mg²⁺ions,the suitable conditions for the process were determined.That is,8500 mg/L CaO and 3500 mg/L Na2CO3 were added at room temperature,stirred for 40 minutes,then 2 m L of 3‰PAM solution was added,and the mixture was stirred quickly at 200 r/min for 40 s and then slowly at 70 r/min for 6 min.Under this condition,the total removal efficiency of Ca²⁺and Mg²⁺ions in wastewater can reach 97%.The feasibility of treating phosphate rock reverse flotation wastewater with phosphate tailing powder instead of zeolite powder was verified,and the recyclable times of phosphate rock reverse flotation wastewater treated by phosphate tailing powder ballasted flocculation sedimentation method were investigated.The test results showed that it was appropriate to recycle for 4 times.The effect of wastewater treatment was investigated through reverse flotation test.The test results showed that magnesium removal efficiency of phosphorus concentrate was greatly improved after wastewater was treated by different treatment methods and reused.The reverse flotation index of effluent treated by"tailings powder loading flocculation sedimentation"was even close to that of clean water.It can be seen that"tailings powder loading flocculation sedimentation"and"double alkali+PAM"were technically feasible to treat phosphate rock reverse flotation wastewater.Finally,the reagent costs of the two methods were calculated respectively.The results showed that the reagent costs of the two methods were very close.