N-Cetyltrimethylammonium Bromide-Modified Zeolite Na-A from Waste Fly Ash for Hexavalent Chromium Removal from Industrial Effluent

Abstract

Chromium ions released into aquatic environments pose major environmental risks, particularly in developing countries. Here, a low-cost N-cetyltrimethylammonium bromide (CTAB)-modified fly ash-based zeolite Na-A (CTAB@FZA) was prepared for the treatment of industrial wastewater contaminated with Cr(VI). CTAB@FZA was evaluated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), which showed that CTAB intercalation and coating of the modified zeolite were successful. The effects of influencing variables on the removal of Cr(VI) using CTAB@FZA were also evaluated, including pH, initial concentration, time, temperature, and coexisting ions. Fast adsorption equilibrium was observed after less than 10 min, and CTAB@FZA had a maximum adsorption capacity of 108.76 mg/g and was substantially greater than that of pristine FZA following modification. Furthermore, isothermal and kinetic data demonstrated that Cr(VI) adsorbed onto homogeneous surfaces via rate-limiting monolayer Langmuir adsorption, and according to thermodynamic data, the sorption of the targeted pollutant was exothermic and spontaneous. The application of CTAB@FZA to industrial wastewater treatment yielded Cr(VI) concentrations that were below the USEPA standards. Overall, the findings demonstrated that CTAB@FZA is an effective, promising, and economical adsorbent for the treatment of Cr(VI)-polluted water.