Thermodynamic Properties of Chromium (III) Ion Adsorption by Sweet Orange (<i>Citrus sinensis</i>) Peels

Abstract

The adsorption of Cr (III) ion from aqueous solution using orange peels as adsorbent was investigated using batch equilibrium technique. The research is significant as it's aimed at investigating the suitability of orange peel, a waste product as adsorbent for the adsorption of Cr (III) ions from aqueous solution. Orange peel as an adsorbent is resource-saving and has an environmental friendly behavior. Adsorption envelope experiment was conducted using a constant Cr (III) ion concentration of 0.1 M, adsorbent dose of 2.5 g and a temperature of 30˚C at varying solution pH of 2, 4, 7, 9 and 12 respectively with pH of 2 having the highest adsorption and therefore it was selected for use in the adsorption isotherm experiment. Adsorption isotherm experiment was conducted at varying temperatures (30˚C, 40˚C, 50˚C, 60˚C), concentration (0.1 M, 0.2 M and 0.3 M) Cr(NO3)3. Thermodynamic parameters such as ∆G, ∆H, ∆Hr, ∆A, and ∆S were calculated from the experimental data which showed that the adsorption process is feasible, spontaneous and followed physisorption mechanism 9H 2 O and adsorbent dosage (1 g, 1.5 g and 2 g) respectively. The experimental results were tested using Langmuir, Freundlich, Linear and Temkin adsorption isotherm models. The experimental data best fitted the Freundlich isotherm model. The experimental results revealed the suitability of orange peel which is a waste product as effective adsorbent for the sorption of chromium (III) ions from aqueous solution.

Biosorption of an Anionic Dye, Eosin Yellow onto Pineapple Peels: Isotherm and Thermodynamic Study

“…A sample of about 2 kg (estimated to be enough for the entire sorption process) was collected and air-dried in the laboratory at room temperature for five days. The sample was then pretreated according to the method reported by [12]. The sample was then passed through a 0.112 mm mesh sieve and used for subsequent experiment.…”

“…The amount of the dye adsorbed by the adsorbents at equilibrium was determined using the mass balance equation (equation 1) [12]. The data generated from this experiment were then used to study the various thermodynamic parameters.…”

“…The model assumes uniform energies of adsorption onto the surface and no transmigration of adsorbate in the plane of the surface [12], [19].…”

“…In an effort to examine in greater details the effect of temperature on the sorption of EY by pineapple peels, thermodynamic parameters such as Gibb's free energy change (G), enthalpy change (H) and entropy change (S) were estimated using equations 5, 6 and 7 [12], [22].…”

“…These low-cost adsorbents are majorly biological/agricultural wastes either in a raw or modified form such as orange peels, mango peels, saw-dust, rice husk, coconut coir, date palm seed, maize cob, sugarcane bagasses, egg shell, plantain peels, cassava peels etc. [2], [12], [13]. In the present study, pineapple peels (PP) is been investigated as an alternative adsorbent.…”