Removal of chromium from aqueous solution using a nanocomposite of nickel ferrite and polyaniline doped with 2-naphthalene sulfonic acid

Chromium is a highly toxic, highly mobile heavy metal commonly found in industrial effluents. This study investigated the efficacy of a nickel ferrite/polyaniline/2-naphthalene sulfonic acid nanocomposite (PANI-NSA/ NiFe2O4) in removing Cr(VI) from solution. NSA doping led to the formation of tubular-shaped rods, enhancing the material's surface area. Key adsorption parameters (pH, adsorbent dosage, agitation time, and initial pollutant concentration) were thoroughly examined and optimized. The adsorption process was notably pHdependent, with maximal adsorption occurring at pH 2. The findings indicated a remarkable 99.9% removal of Cr(VI) from a 50 mg/L solution with a 25 mg adsorbent dose. Freundlich, Langmuir, and Two-Surface Langmuir isotherm models were tested, with the Two-Surface Langmuir model best describing the experimental results. Kinetics studies revealed rapid adsorption within the initial 30 min, followed by a slower rate, reaching maximum Cr(VI) removal within 24 h. Temperature studies revealed and enhanced adsorption capacity at higher temperatures, with a maximum adsorption capacity of 420.0 mg/g at 45 degrees C. Thermodynamic analysis indicated an endothermic and spontaneous adsorption process. The mechanism of Cr(VI) removal involved electrostatic attraction, reduction, and surface complexation. PANI-NSA/NiFe2O4 could be reused for up to five cycles, achieving 99% Cr(VI) removal from a 50 mg/L Cr(VI) solution in the first two cycles. Furthermore, tests on authentic chromium wastewater showed that a 40 mg dose in 50 mL liquid fully removed 50 mg/L Cr(VI). This study underscores the potential of PANI-NSA/NiFe2O4 for industrial applications in Cr(VI) removal, offering a promising solution for addressing the pressing issue of chromium pollution.