Preparation Of Zeolites Form Potassic Rocks And Their Adsorption Performance

Potassic rocks are the aluminosilicate mineral containing Si,Al,K elements,and are abundant in China.The synthesis of zeolite from potassic rocks is of great significance for the comprehensive utilization of aluminosilicate minerals and the low-cost synthesis of zeolite.To make full use of the resources in the potassic rocks,the spherical hydroxycancrinite and W zeolite were prepared from the potassic rocks,and the removal of harmful substances in water was studied via the synthesized zeolites.Spherical hydroxycancrinite was prepared by a hydrothermal method from potassic rocks activated by sub-molten salts.The effects of reaction temperature,reaction time and n（H₂O）/n（K₂O）on the synthesis of spherical hydroxycancrinite were investigated.The suitable conditions for the synthesis of hydroxycancrinite were determined as follows:n（H₂O）/n（K₂O）=38.62,the reaction temperature was 150°C and the reaction time was 12 h.The activated potassic rocks were firstly transformed to hydroxysodalite during the hydrothermal reaction,followed by the formation of the spherical hydroxycancrinite under the salting out effect of K⁺.High value-added calcium silicate hydrate was prepared from the synthesized filtrate,and the mother liquor recycling process was designed.Low-cost hydroxycancrinite prepared from potassic rocks exhibited excellent adsorption performance for Cu（II）with the maximum adsorption capacity of 51.76 mg/g at 25℃,and showed good cyclic regeneration ability.The W zeolite was prepared by a hydrothermal method using potassic rocks activated by alkali fusion as the raw material.The effects of alkali ore ratio,reaction time,n（H₂O）/n（Si O₂）on the synthesis of W zeolite were investigated.The suitable conditions for the synthesis of W zeolite were described as follows:alkali ore ratio of 1.25,reaction time of 12 h,n（H₂O）/n（Si O₂）=25.83,and reaction temperature of 150℃.Compared with other hydrothermal methods,the method could greatly shorten the reaction time,reduce the liquid-solid ratio of the reaction system,showing a great application prospect.After modification of W zeolite,W zeolite presented K⁺exchange capacity of 48.58 mg/g in simulated seawater.In addition,the prepared W zeolite showed a good slow release performance of K⁺in soil.In order to avoid waste of resources,the recyclic utilization process of the mother liquor after the synthesis of W zeolite was designed.Chitosan/W zeolite（CW）composites were prepared from chitosan and W zeolite.CW composite and W zeolite were used for the adsorption of Congo red（CR）and Zn（Ⅱ）in aqueous solution,respectively.The effects of p H,adsorption time and solution concentration on the adsorption performance were investigated.CW composite exhibited the best adsorption performance for CR with the maximum adsorption capacity of 158.99mg/g under the conditions of p H=3 and the equilibrium time of 240 min,and W zeolite showed the maximum adsorption capacity of 70.78 mg/g for Zn（Ⅱ）under the conditions of p H=7 and the equilibrium time of 120 min.The adsorption process could be well described by pseudo-second-order kinetic model and Langmuir isotherm adsorption model.CW composite and W zeolite showed the excellent adsorption performance after four recycle use.CW composite completed the adsorption of CR through hydrogen bonds,electrostatic interactions.