The Depth Of Biological Agents, Purification Of High Concentrations Of Heavy Metals In Wastewater

The heavy metal wastewater pollution is a very serious environmental problem that every metallurgical enterprise of nonferrous metals has to face to nowadays. Even though it can match the discharging standard, the quantity of discharging is huge. Furthermore, a large number of raw materials are lost. Therefore it is hard to recycle. All elements mentioned above increase the cost of dealing with them. In the case study of ZhuZhou Smelt Group, it targets to the solution of heavy metal wastewater in high concentration. A method called "No-formulation A" is proposed to handle this issue. Based on the calculation of heavy metal ions thermo dynamical theory, a new craft, "bio-formulation A coordinating - two-stage hydrolysis - removal calcium ion deeply", is contrived through heavy metal ions thermodynamics study in advance, validating researches time to time inthe laboratory and expands experiment on-the-spot. The results can be explained as followed:(1) Diagrams for the concentration of complex ions pc-pH, the ratio of four kinds of hydroxy complex ionsα_n-pH, conditional solubility product of their hydrates to pH in their system were drawn respectively. The relationship between the equilibrium concentration of total heavy metal ions and pH is illustrated in Me²⁺-H₂O system, when dissolution of hydrate is in equilibrium. The solubility of Zn(OH)₂ is at the minimal level at pH range of 8.35 to 10.82, of which Cu(OH)₂ is at 7.32 to 10.68, Cd(OH)₂ is from 9.84 to 13.31, and pH of Pb(OH)₂ is from 10.096 to 10.997. The diagram forα_n-pH shows that each hydroxy complex ion exists in the system depends on an optimized pH value. The diagram for the conditional solubility product pPs-pH indicates that the pPs reaches minimum at the pH range of 8.0 to 9.0 in Zn²⁺-H₂O system, 7.0 to 9.0 in Cu²⁺-H₂O system, 9.5 to 10.5 in Cd²⁺-H₂O system and 10.3 to 11.2 inpb²⁺-H₂O system.(2) The influence factors, containing quantity of bio-formulation A, coordinated and hydrolyzed time of reaction, hydrolyzed final pH value, PAM dose and temperature, were examined. Technical parameters are set to following values: bio-formulation A is 0.5, coordinated time is 15min, hydrolyzed time is 5min, hydrolyzed final pH value is 10.0, PAM dose is 0.6rag/L, the whole response procedure is not affected too much by temperature. Concerning several essential influence factors, a four-factor-three-level experiment is designed, the results are analyzed by limiting value calculating and variance analysis calculating. The concentrations of Zn²⁺ and Cu²⁺ ions vary at different factors and different levels, but they can all reach the standard of national drinking water source. Final pH value hydrolyzed is the first factor to be considered. The quantity of bio-formulation A is the second one. Coordinated time is not much important with hydrolyzed time.(3) The flowchart of "bio-formulation A coordinating - two-stage hydrolysis - calcium removal deeply" is examined. There are three buffered areas in the aqueous solution: pH is form 3 to 4 in the first area, from 6 to 8 in the second one and from 11 to 12 in the last one. The concentration of Zn²⁺, Cu²⁺ ions can be reduced to the standard of national drinking water source, which means the concentration of Pb²⁺ ion is around 0.05mg/L closed to national drinking water standard. The concentration of Cd²⁺ ion is approximate 0.05mg/L. The concentration of calcium ion can be removed to any level by alkali dreg.(4) The system of the optimized pH value controlled by Ca(OH)₂ and NaOH as neutralizer can keep the equilibrium by recycling the concentration of sulphur acid radical and Na⁺ ions, which can avoid being accumulated. The concentration of SO₄^2- remains within 2000mg/L.(5) Bio-formulation A is a kind of hydroxyl-containing colloid particle through XRD analysis of waste residue, EDX and FTIR is extrapolated. The electronic structure of Oxygen atoms in the hydroxyl is ls² 2s² 2p_x² 2p_y¹ 2p_z¹. Electrons outside the oxygen atom are heterocyclic state of sp³, two of which occupy sp³ heterocyclic orbit. Under normal temperature condition, bio-formulation A can transform to bio-coordinated compound with heavy metal ions which contains hydroxyls, carbonyls, C-H bond, SO₄^2-, etc. Bio-formulation begins to hydrolyze when pH ranges from 3 to 4, which makes bio-coordination to become steady compound which is indiscerptible and contains many kinds of elements (such as Mn, Si, Mg, A1, O, S, Pb, Cd, Ca, Fe, C, Cu and Zn), therefore the heavy metal ions are removed efficiently.(6) The result of expanded experiment on-the-spot is approved by the authority that bio-formulation A can treat with heavy metal wastewater which is acid and full of calcium ion directly. The concentration of every kind of heavy metal ions can reach the National standard of drink water resource (CJ3020-93). The concentration of calcium ion can be controlled.