Phenol and/or Zn2 + adsorption by single- or dual-cation organomontmorillonites

Abstract

Single- or dual-cation organomontmorillonites (OMt) modified by one or two cationic surfactants, respectively and/or cysteamine hydrochloride (CSH) were used to remove Zn2+ and/or phenol from aqueous solutions. The OMt were characterized by XRD, FTIR spectroscopy and N2 adsorption-desorption isotherm analyses. The adsorption results of Zn2+ and phenol showed that OMt had much larger adsorption capacities of phenol than that of Na+-Mt or CSH-Mt in the presence of Zn2+. Experiments with the simultaneous presence of both the contaminants showed that one did not affect the adsorption of the other with all the adsorbents. The uptakes of Zn2+ and phenol onto dual-cation OMt increased with increasing solution pH, contact time, temperature and initial concentration of Zn2+ and phenol. The adsorption equilibrium time was 10min for both contaminants and the maximum adsorption capacities of Zn2+ and phenol were found under alkaline environment. The adsorption of both Zn2+ and phenol can be better described by Freundlich model than Langmuir isotherm. Phenol adsorption onto OMt was caused primarily by partitioning into an organic phase in the interlayers, and the uptakes of phenol increased with increasing alkyl chain length and loading amount of surfactant in single-cation OMt. Zn2+ adsorption onto dual-cation OMt was due to ion exchange, formation of complexes and/or precipitation mechanism depending on the solution pH.