Sorption of ß-naphthalene sulfonic acid by weak base anion exchangers as controlled by alkyl chain length of the amine functional group
Weak base anion exchangers are promising for decontamination of aromatic ionizable organic compounds (AIOCs) from industrial wastewaters. However, the effect of alkyl chain length of an amine functional group of resins on decontamination process has rarely been clarified to the best of our knowledge. In the present study, a commercially available weak base anion exchange resin D301 and two newly synthesized ones AEC-2 and AEC-4 with a varying alkyl chain length of amine functional groups (derived from dimethylamine, diethylamine and dibutylamine, respectively) were used for adsorption of ^-naphthalene sulfonic acid (NSA). Adsorption isotherms and influence of solution pH, temperature, time and coexisting competitive inorganic salt (Na 2 SO 4 ) on adsorption behavior were investigated and the column adsorption-regeneration tests were carried out. Results showed that adsorption selectivity for NSA over sulfate increased with increasing the alkyl chain length in the high saline water. But the sorption velocity decreased to a moderate extent with increasing the alkyl chain length. Thermodynamic parameters indicate that adsorption is an exothermic and spontaneous process, and NSA adsorption onto AEC-4 is an enthalpy-driven process, while that of D301 as well as AEC-2 is an enthalpy- and entropy-driven simultaneous process. Further, results of column tests validate long alkyl chain enhancing the sorption selective for NSA and suggest the sorption process can be reversible.
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