Prepaartion Of Zeolite From Bentonite

Bentonite is a kind of mineral resource which has excellent physicochemical properties,low price and abundant storage. It can be used to prepare various deep processing productssuch as silica, organic bentonite, composite material and so on. It opened up a new approachfor exploitation and utilization of bentonite by producing zeolite and provided a rich and cheapmaterial for zeolite synthesis.This paper mainly studied on the synthesis of zeolite by straight-alkali-dissolve and hightemperature alkalifusion activation-hydrothermal process with bentonite as raw material.Effects of synthetic route and technological conditions to the physical and chemical propertiesof products were investigated systematically. The results were as follows:Using hydrothermal process of straight-alkali-dissolve to synthesize zeolite4A, effects ofsynthesizing technological parameters to the property of product was discussed.The resultshowed that at the optimal condition of the nNa₂O/nSiO₂=2, nSiO₂/nAl₂O₃=1.5, nH₂O/nNa₂O=60, crystallization temperature90℃, reaction time6h, zeolite4A with high crystallizationdegree and calcium ion exchange capacity of293mg CaCO₃/g was obtained.High temperature alkalifusion hydrothermal process was adopted to synthesize zeolite4Aand NaOH was chosen as the activator. The effects of activation temperature and materialconstituent on the structures and properties of zeolite4A were discussed. It was found that thereaction activity of material and crystallinity of products were improved by alkalifusion athigh temperature. When the calcination temperature was600℃, composition of material werenSiO₂/nAl₂O₃=1.5, nNa₂O/nSiO₂=3, nH₂O/nNa₂O=50, reacting6h at90℃, zeolite4A withgood quality of well organized crystal shape and the crystal size was less than2μm wasobtained The calcium ion exchange capacity of the product achieved314mgCaCO₃/g.The activated mechanism of one–step alkalifusion hydrothermal method which usedNaOH as activator was studied by TG-DTA and XRD. The material components which usedto synthesis zeolite4A were optimized. It was showed that the mineral structure of bentonitewas destroyed by high temperature reaction of Na₂CO₃and materials. The sodium silicate andsodium aluminate with high reaction activity were produced and activation effect was achieved. The calcination temperature controling at800℃, nSiO₂/nAl₂O₃=1.5, nNa₂O/nSiO₂=3, nH₂0/nNa₂O=50, also can achieve a good zeolite product with high calcium ion exchangecapacity of302mg CaCO₃/g.The synthesizing of P-type zeolite with alkali fusion and high temperature alkali fusionhydrothermal process was discussed preliminarily. Study showed P-type zeolite with highcrystallization degree can be got from bentonite by activited at high temperature by sodiumcarbonate.The simulated copper wastewater was processed with zeolite4A synthesized by hightemperature alkalifusion. The results showed that when the copper ion concentration was600mg/L, pH was adjusted to6.0and0.4g zeolite was added into50mL waserwater toadsorb40min, the removal rate of copper ion was more than99%.This research synthesized high quality zeolite4A by one–step alkali fusion hydrothermalmethod. It avoided second-add and the difficult to activate some aluminum sources, simplifiedthe synthesis technology of conventional alkali method and the production cycle wasshortened. It has directive significance in reducing production costs of zeolite4A andimproving economic efficiency.