Anti-scaling Study On Phosphate Flotation Waste-water

The increase of the phosphate flotation wastewater recycling will lead to the wastewater in the presence of Ca²⁺,Mg²⁺,PO₄^3-and SO₄^2-.Then the wastewater accumulated a large number of ions,resulting in scaling of equipment.To reveal the mechanism and effect of the equipment,which can provide basic data for the treatment and clean utilization of phosphate rock,the research was carried out on anti-scaling of equipment in the circulating utilization of phosphate flotation wastewater.This paper carried out the research on the simula tion of scaling and anti-scaling,based on the analysis of the water quality and the scale of the flotation wastewater from a phosphate plant in Guizhou Province.Adopt the hanging weight,induction time and static experiments to study the pipe scaling behavior with phosphate flotation waste-water.The performance of of PBTCA?2-phosphonobutane-1,2,4-tricarboxylic acid?,HEDP?1-hydroxyethylidene-1,1-diphosphnic acid?,ATMPA?Amino Tri-Methylene Phosphonic Acid?,PASP?poly-aspartate?and PESP?Poly-epoxysuccinic acid?was validated to select high scale inhibition efficiency.Its scale inhibiting mechanism was investigated with Zeta potential,turbidity value,XRD?X-Ray Diffraction?and SEM?Scanning Electron Microscope?.The experimental results showed that the compound of PBTCA and HEDP has more favorable properties of scale inhibition than its components for simulative waste water and flotation waste water.The effects of hardness,alkalinity,and temperature of solution on the scale inhibition rates of scale inhibitors are comparatively high.The CaSO₄·2H₂O samples was analyzed prepared by after addition of those scale inhibitors to examinate Zeta potential,the turbidity value of solution,XRD and SEM,the results indicated that:PBTCA?ATMPA and HEDP have good performance to inhibit scale in pipe.When the dosage reaches 10.0mg/L,the scale inhibition efficiency will be more than 90.0%.The effects of hardness,alkalinity,and temperature of solution on the scale inhibition rates are comparatively high.The effects of organic on the scale inhibition rates is little high.The reason may be that organic anionic collector as a surface active agent,can adsorption in carbon steel metal surface adsorption layer.It shown that the surface of carbon steel specimens from the macro have scaled.Under dynamic conditions to achieve a better scale inhibition effect of anti-scaling agent can be reduced.Cycle time,the water flow velocity and the water temperature are variables and the response is the specimens of20#carbon steel surface fouling quantity,there is no significant difference among two interaction.Those three kinds of scale inhibitor by the static scale inhibition mothed have good performance tof phosphate rock flotation waste water.Those have no effect on the flotation indexes.The results showed that inhibition efficiency and induction time was gradually improved with the increase of scale inhibitor concentration.Using crystallization equations that relate induction times with supersaturation ratios,the free energy barrier,nucleation rate and critical nuclei radius were calculated with and without addition of a scale inhibitor.Gypsum dihydrate morphology changed from needle-like in the absence of scale inhibitors to tabular in the presence of ATMPA.ATMPA was adsorpted on the surface of gypsum dehydrate.This is in Langmuir?Freundlich and Temkinadsorption model.H<0 and S>0indicated that the adsorption is spontaneous exothermic reaction.Zeta potential analysis results show that this is electric double layer adsorption.XRD results show that the scale inhibitor will cause the crystal morphology change.Laser particle size analysis results show that after adding the anti-scaling agent ATMPA fouling material particle size has changed more large compared with the blank group.Through the SEM observation,the morphology of the crystal has changed.The crystal without any scale inhibitor was needle-shaped,this shape was more likely to scale on the solid surface;after adding scale inhibitor it became granular or short flat,was not conducive to the formation of fouling on the solid surface.Due to the growth of calcium sulfate crystals is in strict accordance with a certain crystal lattice forming a dense and hard crystal.After adding scale inhibitor,the scale inhibitor is adsorbed on the crystal and doped in the lattice.As results of interfering with the growth of CaSO₄·2H₂O crystals and distorting the crystal morphology are that the crystal internal stress become increasing,the surface becomes loose porous,the crystal is easy to break into a granular or short flat shape and hinder the growth of CaSO₄·2H₂O.