Natural ferruginous manganese ore as a potential low-cost adsorbent for Congo red dye removal from aqueous solution

Abstract

In the present work adsorption characteristics of natural ferruginous manganese ore (FMO) was investigated to assess its potential as an efficient and economic adsorbent for Congo red (CR) dye removal from the aqueous solutions. The characterization of FMO was initially performed using different analytical techniques of XRD, XRF, SEM-EDS, FTIR and pH PZC. The effects of different adsorption parameters, such as, pH, adsorbent dosage, initial dye concentration, contact time and temperature were further investigated in detail. The equilibrium time required to reach maximum uptake was noted at 90 min with 83% removal efficiency. The mean free adsorption energy (E) estimated using D-R model was 1.12 kJ.mol−1 indicating the physical adsorption of CR on FMO. The adsorption data showed a good fitting to the Langmuir isotherm model and pseudo-second order kinetic model with higher regression-coefficient (R2). The adsorption process thermodynamics parameters (∆H, ∆S and ∆G) revealed endothermic and spontaneous nature of reaction accompanied by entropical changes occurred at solid-solution interface. The maximum adsorption capacity of FMO was observed to be 76.9 mg g−1 which is well comparable to the values reported in literature. It is necessary to mention that we are reporting first time the potential of FMO as adsorbent for CR removal and results would be of great importance for the application of FMO for environmental decontamination.