Effect of poly-aniline coated iron ore mining waste (PANI@IOMW) as efficient adsorbent on mitigation of Cr (VI) from aqueous solution: Experimental and statistical investigation

Abstract

Present investigation is focused on the synthesis of poly-aniline coated iron ore mining waste (PANI@IOMW) adsorbent and its utilization for remediation of Cr (VI) from water using batch process. The studied adsorbent shows excellent Cr (VI) mitigation properties with highest efficiency of 99% at significantly low dosage of 0.15 g, pH 2.0, 90 min contact time and 50 mgL−1initial concentrations. Non-linear regression analysis shows that Freundlich isotherm is considers as a suitable model for mitigation of Cr (VI) with Qmax of 73.29 mg/g for 50 mgL−1 Cr (VI) concentration. Pseudo second order kinetics model is considered as a best fitted model for the present investigation. Thermodynamic study shows that adsorption is spontaneous and endothermic in nature. The value of mean free energy (0.983 J/mol at 303 K) and activation energy (7.96 kJmol−1 at 303 K) shows that adsorption of Cr (VI) on PANI@IOMW occurs through physisorption. Surface study of PANI@IOMW was done using FESEM, EDX, FTIR, XRD, XRF, XPS, HR-TEM and AFM analysis. The comparison of % efficiency of Cr (VI) removal obtained by response surface methodology (RSM) (99.06%) and experimental studies under the optimum conditions (99%) suggested that quadratic model is suitable model for Cr (VI) adsorption. The adsorbent PANI@IOMW shows regeneration ability up to two cycles without losing its properties. Thus PANI@IOMW adsorbent can be used for treatment of water containing Cr (VI) as good alternative as compared to chemical adsorbents used by the industries.