Preparation and application of organo-minerals as sorbents of phenol, benzene and toluene

Abstract

Nonionic organic contaminants (NOCs) such as benzene, phenol, and toluene from contaminated wastewater can be effectively sorbed by organo-modified minerals. Organo-minerals were prepared from Na-montmorillonite, sericite, and zeolite by exchanging quaternary ammonium cations with various molecular weights such as Benzyldimethyltetradecylammonium (BDTDA), Hyamine 1622®, and Benzyltrimethylammonium (BTMA). The adsorption capacity of these organic cations onto these minerals is in the order of montmorillonite>zeolite>sericite, which is mainly dependent on the Ca/Mg cation exchange capacity (CEC) of each mineral. The interlayer expansion of the basal spacings of BDTDA- and Hyamine-montmorillonite increases from 12.5 to 30.8 Å as the amount of interlayer organic cation increases. BTMA-montmorillonite is characterized by less interlayer expansion. The aliphatic tale on the BDTDA ion apparently contributes to the multiple interlayer sorption in BDTDA in contrast to BTMA's reluctance to sorb a second interlayer. The exchange capacity of organic cations onto montmorillonite and the interlayer expansion of organo-montmorillonite correlate with the sorption of phenol, benzene, and toluene. BDTDA-, Hyamine-, and BTMA-montmorillonite complexes include benzyl functional groups and are effective sorbents for NOCs such as phenol, benzene, and toluene in aqueous solutions and may have practical applications in wastewater purification. The BTMA-zeolite complexes have potential for application as a sorbent for phenol. Organo-sericite complexes were the least effective sorbents of the three minerals tested. Comparison of the three NOCs with activated carbon indicates that these organo-mineral complexes all fall short of sorbing as did the activated carbon. BDTDA-montmorillonite stands out as the best performing product and it improved with each addition of surfactant to about 70% of the activated carbon sorption of benzene and 66% of toluene. BTMA-zeolite sorption was 65% of the sorption of the activated carbon for benzene and about 50% of the activated carbon sorption of toluene. Phenol was sorbed little on the untreated zeolite or sericite surfaces and poorly on the organo-mineral phases except that the BDTDA- and BTMA-montmorillonite sorbed about 35% as much phenol as sorption by activated carbon.