Preparation And Lead Ion Adsorption Test Of Magnesium Matrix Material Modified By Phosphorus As Wellas Porous Silica Doped With Magnesium

Ordinary magnesium oxide materials have strong adsorption capacity for heavy metals,but they have some problems such as high residual rate of lead ions after adsorption at low concentration and difficulty in recovery.To enhance the adsorption capacity of magnesium oxide materials under ultra-low concentration of lead ions,a series of phosphorylated modified magnesium-based materials were synthesized by methanol method,and the influence of solvent thermal temperature,solvent type and phosphorus content on the adsorption performance of lead ions was discussed.The addition ratio of phosphoric acid to methanol was 0.005,0.01,0.02,0.03and 0.05,and the corresponding materials were denoted as Mg-0.25P,Mg-0.5P,Mg-1.0P,Mg-1.5P and Mg-2.5P.To implement the functional application in adsorption column,porous silica material doped with Mg were prepared by sol-gel method.The factors affecting the porosity of materials were discussed by adjusting the concentration of polyethylene oxide?PEO?and the ratio of acid solution to tetraethyl orthosilicate?TEOS?.On this base,magnesium was loaded in three stage:before sol-forming?SF?,after solvent exchange?SM?and before calcining?SL?.The results showed that the main crystal of Mg-1.5P are Mg₂PO₄?OH?and MgO,the adsorption capacity of lead ions increased firstly and then decreased with the preparation temperature,the adsorption capacity is relatively high in 90?.Mg-0.5P?MgO?,Mg-1.0P?MgO?and Mg-1.5P?MgO?performed better in adsorption capacity than Mg-0.25P?MgO?and Mg-2.5P?MgHPO₄?.Calcination of 600?plays an important role in the phase structure and adsorption activity of the material.The adsorption research showed that the adsorption process satisfied pseudo-second kinetics,and the adsorption equilibrium was basically reached at 60 min.The adsorption process also satisfied Langmuir adsorption.The calculated value of Langmuir adsorption under 30?,40?and 50?is 2849.39mg/g,3291.89 mg/g and 2742.67mg/g,respectively,the adsorption value of 40?is much higher.Compared with pure MgO,this material has better adsorption effect at low concentration of lead ions.The residual concentration of lead ions after adsorption by material with phosphorus content of 0.5 ml and 2.5 ml is 1.99 ppb and 7.03ppb,lower than 35.17 ppb by pure MgO,and lower than 10 ppb of drinking water standard.PEO and acid/TEOS ratio are the key factors affecting the porosity of silica materials.The main component in SF material was SiO₂,and the adsorption rate was lower than 60%.In addition,MgO crystal peak appeared in SM materials with an adsorption rate up to 95%.The crystal peak of Mg₂SiO₄ appeared in SL materials,and the adsorption rate of lead ions was greater than 96%.The adsorption of lead ions by SL-4 materials meet the pseudo-second order kinetics,and the adsorption equilibrium was reached after 60 min.Materials meet the Langmuir adsorption,and the calculated value of Langmuir adsorption under 30?,40?and 50?is 909.09 mg/g,943.39 mg/g and934.58 mg/g,respectively.The flow adsorption test of SL materials showed that it still owned adsorption stability after 20 days and there was no obvious blockage in such adsorption process.