The Poly-hydroxy-aluminum Pillared Diatomite Preparation And Adsorption Characteristic Of Cu²⁺and Zn²⁺

With rapid development of the mining and smelting industries,the pollution of heavy metals in water is getting worse.It's of great significance to control it with effective treatment of wastewater containing heavy metal ions.There are a lot of methods in which the adsorption method is widely used because of its simple operation,stable effect and small secondary pollution,etc.Among various adsorbent materials,diatomite is considered as a good heavy metal ion adsorbent due to its big surface area,rich surface active groups and great many micropores,also its strong negatively charge,large capacity as well as low price.Nevertheless,the natural diatomite contains impurities,and the physical and chemical structure is defected,which restricts its effective adsorption performance.So it's quite necessary to improve the diatomite.In the study,the pillared modification with poly-hydroxy-aluminum is applied to the natural diatomite.Various data is come out of the research of natural diatomite adsorption,the generation research of poly-hydroxy-aluminum pillared diatomite as well as the research of comparison and analysis of diatomite adsorption and its physical and chemical characterization before and after pillared modification.The main results are as follows:(1)The natural diatomite adsorption research indicates that the adsorption capacity of natural diatomite to Cu2+ and Zn2+ decreases after the first increase with the increasing adsorbent concentration,decreases after the first increase with the increasing initial ion concentration,tends to balance after the rapid increase with the increasing adsorption time,increases with the increasing initial solution pH and the solution temperature has little effect on the diatomite adsorption.By optimizing adsorption conditions,the best adsorption condition of natural diatomite to Cu2+ and Zn2+ is:adsorbent concentration 15g/L,3g/L;initial ion concentration 150mg/L,250mg/L;initial solution pH 6.0,6.0;solution temperature 55 ?,45 ?;adsorption time 60min,60min.Under the optimum adsorption condition,the adsorption capacity of natural diatomite to Cu2+ and Zn2+ is 6.244mg/g and 8.950mg/g.(2)The generation research of poly-hydroxy-aluminum pillared diatomite indicates that the adsorption capacity of pillared diatomite to Cu2+ and Zn2+ reduces after the first rise with the rising[OH-]/[Al3+],reduces slightly after the first rise with the rising KCl concentration(potassic alteration),reduces after the first rise with the rising[Al3+]/diatomite,tends to balance after the first rise with the rising reaction temperature,tends to balance after the first rise with the rising reaction time,reduces after the first rise with the rising aging temperature,and reduces after the first rise with the rising aging time.The best generation condition of pillared diatomite is:[OH']/[Al3+]2.2,KCl concentration 1.8mol/L,[Al3?]/diatomite 10mmol/L,reaction temperature 60?,reaction time 24h,aging temperature 200? and aging time 0.5h.(3)The comparison and analysis of diatomite adsorption before and after pillared modification shows,the isothermal temperature adsorption of diatomite to Cu2+ and Zn2+ accords with Langmuir model before and after pillared modification.By fitting,the adsorption capacity qm of pillared diatomite is 7.491 mg/g and 11.312mg/g,which increases 32.9%and 33.3%comparing with the one before pillared modification.The adsorption kinetics characterization of diatomite to Cu2+and Zn2+ can be described by the second order kinetics equation before and after pillared modification.Therefore,pillared modification can improve the diatomite adsorption effectively with almost no influence on its adsorption behavior.(4)The comparison and analysis of diatomite physical and chemical characterization before and after pillared modification shows,the Cation Exchange Capacity(CEC)of pillared diatomite is 9.548 cmol/Kg more than that of natural diatomite with the rise amount to 36.1%.The micro morphology of natural diatomite is mainly round sieve-like,mixed with a small amount of columnar diatomite.After pillared modification,poly-hydroxy-aluminum gets into diatomite to increase the inner space of it.The main component of natural diatomite is amorphous SiO2,also contains small amounts of feldspar.The main hydroxy types of natural diatomite are twin silanol group(= Si(OH)2),coalescence silanol group(Si-O-H...OH-Si=)and the surface-isolated silanol group(?Si-O-H).The hydroxy quantity increases after pillared modification.Some amorphous SiO2 transforms into quartz crystal and the Al2O3 content of diatomite rises after pillared modification.