The Removal Of Phosphate In Water By Ion Exchange Membrane And Modified Cellulose Sponge System

The excessive discharge of phosphorus has caused serious pollution to the water environment in China.Compared with other phosphorus removal methods,the operation cost of biological phosphorus removal is lower,and nitrogen and phosphorus can be removed simultaneously.Under the optimum conditions,the removal rate of phosphorus is higher.However,the effect of biological phosphorus removal is not stable,and may not meet the phosphorus discharge standard.In order to solve this problem,this study used the combined reactor of anion and cation exchange membrane to construct an unpowered enhanced phosphorus removal reactor through the difference of ion concentration intensity,so as to achieve the purpose of phosphorus removal from low concentration phosphorus-containing wastewater.Cellulose sponge,modified by epichlorohydrin and ethylenediamine,was prepared into adsorption phosphorus removal materials to accelerate the phosphorus removal effect of the reactor.At the same time,we achieved the purpose of recovery of phosphorus.The study investigated the effects of different factors on enhanced phosphorus removal reactor and modified cellulose sponge.The results showed that when 1%NaCl was added into the enhanced phosphorus removal reactor,the removal rate of 5.00 mg/L phosphate solution can reach 85%in 4 days,while it can reach 92%in 5 days.Moreover,the content of phosphate was lower than 0.5 mg/L,which can meet the first standard of phosphorus emission.And the phosphorus removal effects of MgCl2 and CaCl2 solutions were better than that of NaCl.For the same kind of salt solution,the phosphorus removal effect of 1%salt solution was better than that of 3%and 5%salt solution.When the temperature of the reactor was 30℃,the phosphorus removal effect was the best.Moreover,the lower the phosphate concentration was,the shorter the time required for phosphorus removal.For simulated domestic wastewater,the time required for phosphorus removal in the reactor was slightly longer,but the removal rate can still reach 93%.For the modification test of cellulose sponge,the phosphorus removal experiments of cellulose sponge under different modification conditions were first carried out.The optimal conditions under each factor were determined.The removal rate of phosphate under single optimal conditions and all optimal conditions was compared.The results showed that under all optimal conditions,the modified cellulose sponge(10 mL epichlorohydrin,40℃,60 min;2 mL ethylenediamine,70℃,90 min),the removal rate was higher and the phosphorus removal effect was better.The phosphorus removal rate of unmodified cellulose sponge was 3%～6%,while its removal rate of phosphate of modified cellulose sponge can reach 91%.The adsorption rate was the fastest at 30 min,and then the adsorption rate decreases rapidly.Temperature had little the effect on the removal rate of phosphate.When the pH was in the range of 5～7,the removal rate of phosphate of modified sponge was up to 76%.Filling CO2 into the solution can also improve the removal rate of phosphate,with a flow rate of 0.1 m/s for 8 min,the removal rate of phosphate was 78%.The modified cellulose sponge was combined with the reactor.For 5.00 mg/L phosphate solution,the removal rate was 90%in three days,which reached the national level emission standards.For treating domestic wastewater directly,the residual phosphate was 0.45 mg/L after seven days,and its removal rate reached 92%.Modified cellulose sponge has accelerated the phosphorus removal efficiency of the reactor.The maximum adsorption capacity of 1 g modified sponge reached 20.98 mg/L within 2 h.In summary,the combined system of ion exchange membrane and modified cellulose sponge had an excellent phosphate removal effect on water.It is of practical significance to solve the problem of difficult removal of low concentration phosphorus at the end of biological treatment wastewater.