Treatment Of Special High Concentrations Laboratory Heavy Metals Wastewater With Multistage Ion-exchange Processes

The discharge and characteristics of wastewater produced from four laboratorieswere analyzed in this study. The results showed that all the laboratory wastewaterincluded heavy metals, acid and alkali solution and organics. The residual liquid ofCOD test from environmental laboratory contains high concentration heavy metalswastewater which demonstrates an unneglect heavy metal pollution(Ag=3300mg/L,Hg=1000mg/L, total chromium=3400mg/L) and a high biotoxicity of5.18mgZn2+/L.High concentrations of heavy metals in laboratory wastewater had become thefocus source of urban sewage. Laboratory wastewater was directly discharged intomunicipal sewers without treatment could cause the potential risks of sludge recyclingand sewage regeneration. In order to reduce the harm of laboratory wastewater, theresidual liquid of COD test from environmental laboratory contains highconcentration heavy metals wastewater was disposed, which had the characteristics ofhigh efficiency and easy maintenance.Chemical precipitation was used to remove Ag+. The results showed that theconcentration of Ag+after precipitation test was0.24mg/L under the operatingconditions: initial concentration Ag+of3550mg/L, NaCl of1.1g/gAg+, settling timeof90min, which reached Wastewater Quality Standards for Discharge to MunicipalSewers (CJ343-2010).Strong acid cation exchange resins D072and DEX-Hg were used to remove Cr3+and Hg2+, alkalescence antion exchange resin DEX-Cr was used to remove hexavalentchromium. D072and DEX-Hg were used to recycle Hg2+and Cr3+, removal rate wasrespectively90%and97%.4%HCl was worked as the regeneration solution torecycle the heavy metal that was absorbed in two kinds of resin. The maincomponents of the recovery liquid were CrCl3and HgCl2which were concentrated the14and17times.The stactic and dynamic test was studied, it contains adsorption and regeneration.The static test results showed that the remove rate of hexavalent chromium fromwastewater was99%under the operating conditions: pH=3, initial hexavalentchromium concentration of500mg/L, volume of hexavalent chromium and mass of resin=166.7ml/g.6%NaOH+10%NaCl was used to recycle hexavalent chromium, thecomponent of recovery liquid which contains Na2CrO4. The dynamic test results showthat the best flow velocity of dynamic test was3BV/h. The drop flow regenerationeffect was better than that of up-flow, which could be condensed88times. Theadsorption properties, physical, chemical structure and mechanism of DEX-Crindicated that the process of hexavalent chromium adsorption was spontaneousendothermic process. Langmuir isotherm was suitable for describing this process.Chemical precipitation and multistage ion-exchange processes were used to treatspecial high concentrations laboratory heavy metals wastewater from environmentallaboratory: chemical precipitationâ†'D072â†'DEX-Crâ†'DEX-Crâ†'DEX-Hg.