Research On The Advanced Treatment To Remove Phosphorus With LDHs Being Modified And Manufactured

Water pollution and water ecology caused by waters eutrophication is becoming more and more serious in our country.The most important reason of waters eutrophication is phosphorus's overproof discharging from domestic wastewater and industrial waste water.This paper aim at removing phosphorus from wastewaterby LDHs'adsorption and recycling it by detaching.Key point of this paper is the investigation of LDHs'adsorbing performance,mechanism of action and influence factor about phosphorus.This paper first make LDHs when the mole ratio of divalent metal ions and trivalent metal ion is 2:1.These LDHs are Mg-Al?Mg-Fe?Zn-Al?Zn-Fe?Cu-Al LDHs.Then test these LDHs'adsorption properties of phosphorus when it's initial concentration is 15mol/L.The results show that Zn-Al LDHs has the most powerful phosphorus adsorption capacity.Contrast SEM photos of this five kinds of LDHs we find that Zn-Al LDHs has the best layered crystal structure and a very big specific surface area.In order to research preparation conditions and adsorption conditions'influences of Zn-Al LDHs'adsorption properties of phosphorus.Making Zn-Al LDHs at different mole ratio,preparation temperature,kinds of coprecipitation agent,aging time and calcination temperature,then use all kinds of Zn-Al LDHs separately to make phosphorus adsorption tests.The results show that Zn-Al LDHs will have the best adsorption properties of phosphorus when the mole ratio of Zn and Al is 2,the preparation temperature is 70?,the coprecipitation agent is 10%NaOH,the aging time is 5h and roasting at 300?.It's adsorption capacity of phosphorus could up to41mg·g^-1.Making Zn-Al LDHs‘adsorption test under the conditions of different initial phosphorus concentration and dosage,shock,grind and different solution pH,the data show that pulverous Zn-Al LDHs will have a higher chemistry equilibrium state when the initial pH is from 6to9 and adsorption time is 16h.It also prove that Zn-Al LDHs has a good alkaline stability and cushioning capacity of acid.Aim at researching coexisting ions'influence on Zn-Al LDHs'phosphorus removal capacity putting some coexisting ions(SO₃^2-?Cl^-?NO₃^-?CO₃^2-?SO₄^2-)in phosphorus solution and observing changes about Zn-Al LDHs'effect of phosphorus removal.The results show that the capability of phosphorus removal will be weakened no matter which kinds of coexistence ion is joined.According influence to sort these coexistence ion is CO₃^2->SO₃^2->SO₄^2->NO₃^->Cl^-,it also proves that Zn-Al LDHs'phosphorus removal capacity not only root in adsorption but also root in ion exchange.From the result of Zn-Al LDHs'desorption and regenerating experiment show that:the best stripping liquid is 10%NaOH,the most suitable temperature of temperature is 300?.When the Zn-Al LDHs be regenerated over 3 times it's adsorption capacity of phosphorus will down to 19mg·g^-1,so the frequencies of regenerating should be no more than 2times.Reclaiming phosphorus of stripping liquid by CaCl₂,the experimental aspect that:it will have the best effect of phosphorus removal when the pH is 11,the mole ratio of Ca:P is 2:1 and the duration of the test is over 25min.Because of the minimum response concentration?MRC?,Ca₅OH?PO₄?₃could be generated only if the concentration of phosphorus more than 10mg·L^-1?So more higher the phosphorus concentration is more better the Zn-Al LDHs'phosphorus removal capacity will be.When the phosphorus concentration is 500mg·L^-1,it's recovery percent could up to 98%.