Response surface modeling of Orange-G adsorption onto surface tuned ragi husk

The paper describes a sustainable way of approach in limiting the dye pollution in surface water systems. An active formaldehyde modified ragi husk (FMRh), a bio adsorbent, was prepared and effectively adopted for the adsorption of Orange-G from aqueous phase. The adsorption data were evaluated using response surface model and created an ideal statistical validation of the significant interactive variables such as pH to 4.8 and contact time to 99.0 min for achieving 100% removal of Orange-G. The kinetic and equilibrium data suited with pseudosecond-order and Langmuir isotherm model with an adsorption capacity of 14.6 mg/g. The Delta G(0) and Delta H-0 values were - 36.1 and - 282.1 kJ /mol, respectively and confirms the spontaneous and exothermic behaviour of the dye adsorption. The FTIR and SEM analysis of FMRh (before and after adsorption) confirms the changes attributed to Orange-G uptake. The kinetically driven adsorptive mechanism holds the dye within the FMRh active-centers.

Automated summary

The paper presents a sustainable approach to limit dye pollution in surface water systems by using active formaldehyde modified ragi husk as a bio adsorbent to effectively adsorb Orange-G dye from aqueous phase. Response surface model was used to optimize interactive variables for achieving complete removal of Orange-G, with kinetic and equilibrium data fitting well with pseudosecond-order and Langmuir isotherm model. The adsorption process was found to be spontaneous and exothermic, confirmed by calculated values of Delta G(0) and Delta H-0, and the mechanism involved the dye retention within the active-centers of FMRh.