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Removal of 2,4-dichlorophenoxyacetic acid from water by modified zeolite adsorbents

Rujikarn Sirival^*, Nopbhasinthu Patdhanagul, Sutthidech Preecharram, Laksanawadee Saikhao

 
ABSTRACT:     The removal of 2,4-dichlorophenoxyacetic acid (2,4-D) by zeolites (ZY, ZY-10, and ZY-200 with Si/Al ratios of 6.07, 14.68, and 207.25, respectively) and modified zeolites with hexadecyltrimethyl ammonuium (HDTMA) were investigated. The influence of HDTMA concentration, modification methodology, and 2,4-D initial concentration were evaluated for 24 h at room temperature (30 °C). The results showed that the best adsorption capacity was obtained from 15 mM HDTMA using a dropwise method and 10 mg/l 2,4-D solution. The best adsorption capacities of the unmodified and modified zeolites were 20.80 ± 0.23, 27.90 ± 0.45, 18.02 ± 0.27, 10.32 ± 0.40, 71.01 ± 0.51, and 99.61 ± 0.36% for ZY, ZY-10, ZY-200, 15MZY, 15MZY-10, and 15MZY-200, respectively. Compared with the unmodified zeolites, the adsorption efficiency of 2,4-D of the modified zeolites was higher except for the MZY, which was due to the steric hindrance caused by blocking of zeolite pores by large HDTMA molecules. The adsorption isotherms of ZY, ZY-10, 15MZY, and 15MZY-10 corresponded to the Freundlich model with the R² values in the range of 0.7922–0.9752. The ZY-200 and 15MZY-200 corresponded to the Langmuir model and showed the R² values of 0.9091 and 0.9589, respectively. The XRD characterization results showed that all unmodified and modified zeolites were similar in crystallinity and the structural framework of zeolite Y. The BET surface area, micropore surface area, and micropore volume of unmodified and modified zeolites were on a downward trend, while external surface area, pore volume, and pore diameter increased.

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* Corresponding author, E-mail: rujikarn.s@ku.th

Received 22 Mar 2020, Accepted 8 Jul 2021