Synthesis and methyl blue adsorption performance of oil shale ash-based zeolites
The structure-function relationship between the type and structure of the oil shale ash-based zeolite and its ability to adsorb dyes is unclear.NaP1,NaX and NaA zeolites were prepared from Beipiao oil shale ash(BPA)and used to adsorb methylene blue(MB).The effects of zeolite dosage,initial MB concentration,pH,adsorption temperature and time on the MB adsorption performance were investigated,and the adsorption mechanism was revealed.The structure-function relationship between the type of zeolite and its ability to adsorb MB was explored.The results showed that the specific surface area and pore structure of the zeolite have great effects on its adsorption capacity.Under the optimal adsorption conditions,the MB removal percentages by NaP1,NaX and NaA zeolites are 99.7％,94.5％and 96.5％,respectively.The synthesized zeolites have excellent recyclability.The adsorption processes conform to the pseudo-second-order kinetic and the Langmuir isothermal adsorption models.The adsorption thermodynamics results show that the MB adsorption on the NaP1 zeolite is a spontaneous endothermic process of increased entropy while that on the NaX and NaA zeolites is a spontaneous exothermic process of decreased entropy.The study of adsorption mechanism showed that electrostatic attraction,hydrogen bond and pore diffusion are the main driving forces during the MB adsorption on the zeolites.This work can provide valuable practical and theoretical reference for the efficient utilization of oil shale ash and low-cost treatment of dyeing wastewater by adsorption method.
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