Technical Study On Adsorptive Treatment Of High Salt Ammonia Nitrogen Wastewater By Copper-loaded Resin

Reduction of ammonia nitrogen emission has become an extremely urgent task since ammonia nitrogen is defined as a emission constraint index in water pollutants from "National12th Five-year Plan". The traditional technologies for ammonia nitrogen removal can not meet the demand in "Plan" and so innovation is required. The ligand-exchange technology has great competitiveness in wastewater treatment process because of its advantage of particular selectivity for target ligands. However, little attention has been paid on research about its use for ammonia adsorption in China.In this paper, a novel ligand exchanger copper-loaded resin with high ammonia selectivity was used as adsorbent and its ammonia adsorption performances were investigated for the treatment of high salt ammonia nitrogen wastewater. The recycling process for ammonia removal by copper-loaded resin includes alkali-pretreatment, ammonia adsorption, ammonia desorption, and water washing. The main results are summarized as follows:The alkali pretreatment for copper-loaded resin was first investigated. The results indicated that the appropriate circulating flow was12L/h and equilibrium time was80min for OH" adsorption. The maximum OH-adsorption capacity of copper-loaded resin was0.93mol/L. The OH-adsorption capacity of copper-loaded resin was not affected by alkali types and didn’t decrease while loaded-copper amount of resin was>1.6mol/kg. The residual ammonia in resin led to the decrease of OH-adsorption capacity.The dynamic performance of copper-loaded resin for ammonia adsorption was evaluated in an ion-exchange column.The results showed that the ammonia adsorption of copper-loaded resin was mainly dominated by the alkali dosage in pretreatment and the free ammonia proportion R(NH3) in wastewater. For the treatment of simulated wastewater containing50g/L Na+and600mg/L NH3-N, the optimal effects were achieved at the alkali dosage of0.75mol/L and R(NH3)=0.5in solution. The effluent NH3-N concentration was below1mg/L, the breakthrough bed volume number was9.10and the ammonia capacity was7.68g/L. The ammonia adsorption capacity improved with the increase of influent ammonia concentration. The existence of Na+lowered ammonia adsorption capacity, but the negative influence wasn’t significant if continued increasing the Na+concentration after Na+>10g/L The use of Ca(OH)2either for resin pretreatment or for the R(NH3) adjustment in wastewater largely restrained the ammonia adsorption of copper-loaded resin. Ammonia adsorption capacity could be improved by higher loaded-copper amount improved. The effluent ammonia concentration couldn’t meet the demand of the emission standard when the residual ammonia amount of the resin was1.48g/L.The regeneration of copper-loaded resin was investigated in a mini fluidized bed. It was indicated that ammonia desorption rate was95.56%under the following conditions that HCl acid was used as the desorbing agent, solution circulating flow was12L/h, desorption time was120min, equilibrium pH was3.8, the solution containing1g/LNa+was used as the washing solution and the washing flow rate was0.9L/h.The cyclic adsorption performance was investigated with the simulated ammonia wastewater containing lOg/L Na+and1000mg/L ammonia. It was indicated that the ammonia adsorption capacity of copper-loaded resin didn’t decrease after5cycles and the ammonia removal efficiency of initial effluent was nearly100%.To be concluded, the technology of ammonia adsorption by copper-loaded resin has the advantages of high selectivity, good effect, simple process and recyclable material. It is effective for the treatment of ammonia-nitrogen wastewater.