Preparation Of Lanthanum Carbonate Adsorbents And Studies Of Their Phosphate Removal Performances

Phosphorus(P),an important cause of eutrophication,is a main pollutant in water.It is a big problem to remove the phosphorus from nature water.Nowadays,the effective technology for removing phosphorus is the adsorption,but the dephosphorization effect of adsorbent is easily influenced by pH which hinder its application in neutral water.And the main purpose of this paper is to synthesize a more efficient lanthanum adsorbent to restore polluted water.This dissertation first examined the dephosphorization effect of Fe3+,Mg2+,Ca2+,La3+and found that La3+ was the most effective element.Then,compareded with the phosphorus removal efficiency of different lanthanum compounds,C-La2(CO3)3 was proved to be most efficient.Sequentially,the preparation conditions of La2(CO3)3 were optimized.After that,metal ions were used to dope La2(CO3)3 for lowering the cost.Finally the iron-lanthanum compound was precipitated on the bentonite,and the dephosphorization effect of that adsorbent was studied.The main contents are generalized as follows:Firstly,the dephosphorization effects of Fe3+,Mg2+,Ca2+ and La3+,in different initial phosphorus concentration,were investigated.Then dephosphorization experiments of C-La(OH)3?C-La2O3 and C-La2(CO3)3 were carried out.The La3+ showed better performance for phosphate removal in neutral condition than Fe3+,Mg2+ and Ca2+.In the pH = 7.5,KH2PO4 solution,C-La2(CO3)3 was most efficient adsorbent,and its phosphate capture capacity calculated from Langmuir model was 66.23 mg/g.Secondly,the La2(CO3)3 was prepared as a novel adsorbent,and its variables have been studied.The optimal condition for preparing La2(CO3)3 was that precipitator was Na2CO3,pH of precipitation was 8,temperature of precipitation was 45 ?,drying temperature was 35 ?.La2(CO3)3 reached adsorption equilibrium in 12 hours;and its phosphate capture capacity calculated from Langmuir model was 112.36 mg/g.Thirdly,uhe metal ions of Ca2+,Mg2+,Fe3+ were used to dope Lak(CO3)3 respectively,and the Fe doped La2(CO3)3 was proved to be best adsorbent.Then its variables were investigated,and the optimal preparing condition is that n(Fe):n(La)is 3:10,pH of precipitation was 8,concentration of metal was 20 mmol/L.Fe-La had higher specific surface area,and its potential zero point rise a lot.Its affinity toward phosphate was high over a wider pH.The phosphate capture capacity of Fe-La calculated from Langmuir model was 101.09 mg/g.Finally,the iron-lanthanum compound was loaded on the bentonite(B-FeLa),which could reach adsorption equilibrium in 4 hours.Besidesd,its phosphate removal rate hardly influenced by pH and the phosphate capture capacity calculated from Langmuir model was 27.86 mg/g.