Adsorption Behaviour of Rhodamine B on Hen Feather and Corn Starch Functionalized with Green Synthesized Silver Nanoparticles (AgNPs) Mediated with Cocoa Pods Extracts

Abstract

This study reports useful application of biodegradable polymeric materials functionalized with silver nanoparticle (AgNPs) biosynthesized from cocoa pods as effective adsorbent for dye wastewater purification. Corn starch and hen feather were functionalized with AgNPs for adsorption of rhodamine B (Rh-B). All adsorbents were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. Decreased intensities of peaks, superior rougher cavities and smaller grain diameter of functionalized biomaterials affirmed the functionalization. Effects of pH, contact time, initial Rh-B concentrations and temperature were investigated and found to be significantly important. Four isotherm models were used to describe the adsorption process with Freundlich being the most suitable for all adsorbents indicating Rh-B adsorbed on heterogeneous multilayer surfaces of adsorbents. AgNPs modification greatly enhanced maximum monolayer adsorption capacities (qmax) of feather (4.27–56.53 mg g−1) and starch (1.176–48.60 mg g−1) by 30- and 40-fold respectively. Kinetic rates of adsorption for starch best fitted Elovich, pseudo first order for feather whereas pseudo second order best suitable for starch-AgNPs and feather-AgNPs. Energies (3.89–7.68 kJ mol−1) of adsorption suggest that adsorption of Rh-B onto the adsorbents was by physiosorption. The negative values of ∆H° and ∆G° imply that adsorption processes were exothermic and spontaneous. Results in this study show that surface functionalization of starch and feather improved their adsorptive performances and will find valuable applications in dye remediation due to their biodegradability and cost-effectiveness.