Novel biosynthesized silver nanoparticles from cobweb as adsorbent for Rhodamine B: equilibrium isotherm, kinetic and thermodynamic studies

Abstract

This study has investigated the adsorption of Rhodamine B (Rh-B) dye on novel biosynthesized silver nanoparticles (AgNPs) from cobweb. The effects of contact time, initial pH, initial dye concentration, adsorbent dosage and temperature were studied on the removal of Rh-B and they significantly affected its uptake. Adsorption isotherms were evaluated using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The adsorption process was best described by Langmuir isotherm with R 2 of 0.9901, indicating monolayer adsorption. The maximum adsorption capacity (q max ) of 59.85 mg/g showed that it has relatively high performance, while adsorption intensity showed a favourable adsorption process. Pseudo-secondorder kinetics fitted best the rate of adsorption and intra-particle diffusion revealed both surface adsorption and intra-particle diffusion-controlled adsorption process. Negative values of thermodynamic parameters (∆H°, ∆S° and ∆G°) indicated an exothermic and spontaneous adsorption process. The mean sorption energy (E) and activation energy (E a ) suggested the uptake of Rh-B onto AgNPs was chemical in nature (chemosorption).

Nanostructured and surface functionalized corncob as unique adsorbents for anionic dye remediation

“…pH pzc plays an effective role in determining the electrostatic surface charge on adsorbent needed for optimum adsorption of the adsorbate. It influences adsorbent surface charge and dissociation of functional groups responsible for adsorption [2,6,8]. Maximum adsorption results at pH < pH pzc for all adsorbents in this study are consistent with the anionic nature of adsorbate and surface charges (cationic) of the adsorbent.…”

“…The favourability of adsorption study is deduced from the values of R L ranging between 0 < R L < 1. In this study, R L was found to be 0.021, 0.012 and 0.074 for CC, FCC and CCNC respectively which is indicative of favourability of adsorption processes on the three adsorbents [8].…”

“…The first rapid part provides the information about diffusion of MO onto the surfaces of adsorbents while the second steady part indicates predominance of intra-particle diffusion [58]. Two-stage plots and deviations from origin suggest that intra-particular diffusion mechanism was involved in adsorption process but not the sole rate-determining step [8,50,57]. Higher values of K 1diff over K 2diff is an indication of greater driving force in the first part than second [58].…”

“…They are better than macro-adsorbents because they possess characteristics such as improved and enhanced reactive binding sites in addition to higher adsorption capacities more suitable for environmental remediation. Recent developments in nanotechnology suggest that water quality problems caused by any class of pollutants could be solved using nano-based materials owing to their greater adsorption capacities associated with their morphology [4][5][6][7][8][9].…”

“…Many studies have demonstrated the effectiveness of nanoparticles for the removal and remediation of pollutants in wastewater. Nanoparticles such as zero-valent silver, zero-valent iron, gold, magnetite, multi-walled carbon nanotube, MgO, NiO, TiO 2 , cobalt ferrite nanoparticles and iron oxide/carbon nanocomposites, γ-Fe 2 O 3 /SiO 2 /chitosan composite, nanoporous core-shell Cu@Cu 2 O nanocomposite and ultrasonic aided nanoparticle stacked activated carbons have previously been deployed as adsorbents to remediate wastewater containing different pollutants with note-worthy results [3,8,[12][13][14][15][16][17][18][19][20][21].…”