Preparation Of Hydrotalcite Loaded Graphene Adsorbent And Its Recovery From Phosphate Adsorption

The necessity of phosphorus in life mainly comes from natural mineral phosphate,mineral phosphate is a kind of non-renewable resource.Global phosphorus resources will creat a shortage in 2035,and people's daily production activity result in a large number of source of nitrogen and phosphorus sources into the water with organic matter with sewage and waste water.Not only caused the waste of resource,but speeded up the process of eutrophication of water as well.So this is a problem that looking for a can effectively remove the high concentration of phosphorus in sewage pollution and recovery of phosphorus resource to be solved at once.Adsorption method has been widely concerned because of its wonderful adsorption and recovery ability.In this paper,graphene and hydrotalcite composite materials are prepared by hydrothermal coprecipitation method,and its phosphorus removal and adsorption property are studied.Based on the adsorption property,the phosphorus recovery effect of composite materials is studied,It provides an efficient and stable means of phosphorus recovery for industrial wastewater containing high concentration of phosphorus.The experimental consequence shows that the optimal mixed amount of palygorskite was 150g/l,the optimal hydrothermal precipitation reaction temperature is 70?,the optimal activation solution and coprecipitation is pH=9,and the optimal mixed amount of graphene was 3.35%.Phosphorus removal rate reaches 43.08%under the most optimal condition.Various characterization methods shows that GR-LDH composite was adsorbed by anionic exchange.The efficiency of adsorption experiment confirms that when the dosage of adsorbent is 1g/l,it can meet China's urban sewage treatment plant discharge level A standard.When the pH of phosphorus solution is 8,the removal rate of phosphate by GR-LDH reaches99.28%.According to the adsorption efficiency study of SO₄^2-,Cl^-,and NO₃^-on phosphate,when the phosphorus solution is 10mg/L,the equilibrium adsorption capacity of the composite is 9.88mg/g;when the phosphorus solution is 25mg/L,the adsorption capacity of the composite is 24.71mg/g;when the phosphorus solution is 50mg/L,the adsorption capacity of the composite is 30.53mg/g.Through adsorption kinetic research,it is found that the quasi-second-order kinetic equation is more consistent with the kinetic characteristic of GR-LDH composite nanomaterial for phosphate adsorption,indicating that the adsorption process of GR-LDH composite nanomaterials is controlled by the chemical adsorption mechanism,namely anionic exchange,and the adsorption process involves electron sharing and move between GR-LDH and phosphate.The adsorption thermodynamic shows that the increase of temperature is conducive to the adsorption of GR-LDH composite on phosphate,and the Langmuir isothermal equation is more consistent with the thermodynamic characteristic of the composite.The composite is adsorbed on a homogeneous monolayer surface.Through the desorption,desorption and regeneration of the composite material study,composite material gets a well desorption effect when the concentration of NaOH is5%;when the desorption time is 60min,the desorption effect of the composite reaches the maximum value of 99.18%.The desorption and regeneration experiment shows that the GR-LDH composite still have more high adsorption,desorption and desorption efficiency after desorption and regeneration for 4 times,indicating that the GR-LDH composite material not only have high efficiency of phosphorus recovery but also have regeneration and reused ability,and have excellent engineering application prospect.Through the study on phosphorus recovery in desorption solution,it is found that the phosphate recovery reaches its peak at pH=13,and when Ca/P is 2,all the phosphate in the desorption solution is recovered.From the recovered component,FTIR analysis shows that the characteristic absorption peak of Ca₅?OH??PO₄?₃ hydroxyapatite appears at1091cm^-1,1033 cm^-1,1,962cm^-1,603 cm^-1,1,565 cm^-1,which provs it is mainly existence.On the basis of the efficiency research of GR-LDH composite material,compares with the common phosphorus removal material"Phoslock"on the market in economics,GR-LDH has better adsorption effect and lower comprehensive cost than Phoslock and own broad development prospect.