Separation Of N-(phosphononmethyl)iminodiacetic Acid Wasterwater By Adsorption

In recent years,the method of iminodiacetic acid(IDA method) is becoming mainprocess of glyphosate（PMG）synthesis, and N-(phosphononmethyl)iminodiacetic acid（PMIDA）is an important intermediate.In IDA method,the step of synthesizingPMIDA will produce a great deal of wastewater,which contains aldehydic,phosphine,salt and so on.Therefore,it is with great economic benefits and environmentalsignificance to study on PMIDA wasterwater utilization.In view of the fact that PMIDA wastewater contains high salinity,PMIDAaqueous solution and PMIDA aqueous solution containing20%sodium chloride wereused as model wastewater,the best adsorbent was selected by comparing the staticadsorption effects of different adsorbents,and factors affecting the adsorption effectswere analyzed;The experiments show that nut shell activated carbon can be arelatively good solution for the adsorption of PMIDA;With increasing concentrationof NaCl,the adsorption capacity of activated carbon for PMIDA from began to declinerapidly into a slow decline,the final equilibrium;When pH is about1,the adsorptioneffect is best,and the best feed ratio is1:3.33(activated carbon:PMIDA); At normaltemperature,it takes6h for the adsorption to reach equilibrium,and with the decreaseof PMIDA initial concentration， the equilibrium absorption capacity reducesaccordingly;In the presence of NaCl,the equilibrium adsorption capacity alsodecreases,but it has no effect on the equilibrium time.The adsorption process accordswith intraparticle diffusion model，liquid membrane diffusion model and first-orderkinetics model;In the experimental temperature range,with the increase of temperaturethe adsorption capacity increased,the adsorption isotherm can be well described byFreundich equation,thermodynamics analysis shows that the adsorption of PMIDA isphysical adsorption.By comparing static desorption effect of different desorption solvent,the bestdesorption agent was selected.Factors affecting desorption effect were studied.Resultsshow that:6%ammonia water is determined as a better desorption solution;consider-ing the economic and the desorption rate,the optimal feed ratio is1:2;In order toobtain larger concentration,1:1is the optimal feed ratio,under the condition,with8.3g/L PMIDA mother liquor as absorption liquid,PMIDA concentration can reach67.82g/L,the desorption rate is80.66%;other impurities in PMIDA mother liquor reduce the adsorption of PMIDA,but the desorption effect isn’t affected;Active carboncan be reused after desorption regeneration.During the dynamic operation stage,the dynamic adsorption breakthrough curvewas mensurated,and factors as flow rate,initial concentration,which influenced thebreakthrough curves were analyzed.The experimental results show that:under thecondition that PMIDA initial concentration was5.054g/L,the flow rate was60mL/h,itreaches breakthrough point and saturation point when the effluent volume were60mLand410mL;With increasing flow rate the curve becomes flatter;With the increase ofinitial concentration,both breakthrough and saturation time becomes shorter;The reuseeffect of carbon column is stable.To study the effect of several modifying agent and microwave modification ofactivated carbon, the results show that: ammonia, urea and load of iron ion onactivated carbon have the better effect and urea is the best, the best modificationconcentration is40%; When radiation power was400w, the effect of microwavemodification is better; urea-microwave modification have a synergistic effect.