Adsorption of Chromium(VI) onto Freshwater Snail Shell-Derived Biosorbent from Aqueous Solutions: Equilibrium, Kinetics, and Thermodynamics

Abstract

In this study, freshwater snail shells (FSSs) containing CaCO3 were used as a low-cost biosorbent for removing Cr(VI) from aqueous solutions. The characteristics of FSS and mechanism of Cr(VI) adsorption onto FSS were investigated. The FSS biosorbent was characterized using nitrogen adsorption/desorption isotherm, X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. The adsorption mechanism was determined by conducting various batch adsorption experiments along with fitting experimental data with various adsorption models. Batch adsorption experiments were conducted as a function of solution pH, contact time, biosorbent dose, and initial Cr(VI) concentration. Results indicated that pH = 2, a contact time of 120 min, and an initial Cr(VI) concentration of 30 mg/L at 20°C were the best conditions for adsorption of Cr(VI) onto FSS. The Cr(VI) adsorption onto FSS decreased with an increase in temperature from 20 to 40°C. The obtained maximum adsorption capacity was 8.85 mg/g for 2 g/L of FSS dose with 30 mg/L of initial Cr(VI) at 20°C. The adsorption equilibrium data fit well with the Sips and Langmuir isotherm models at 20°C with a high R2 of 0.981 and 0.975, respectively. Also, a good correlation between the experimental data and the pseudo-second-order model was achieved, with the highest R2 of 0.995 at 20°C. The adsorption mechanisms were electrostatic interaction and ion exchange. Simultaneously, this mechanism was also controlled by film diffusion. The Cr(VI) adsorption process was irreversible, spontaneous (−∆G°), exothermic (∆H° is negative), and less random (∆S° is negative). In conclusion, freshwater snail shells have the potential as a renewable adsorbent to remove toxic metals from wastewater.

Adsorption kinetics and isotherms of binary metal ion aqueous solution using untreated venus shell

“…In comparison, the samples after adsorption by metal ions showed traced amount of corresponding Cu(II) and Zn(II) being adsorbed, as summarized in Table 2 . The EDX results were in good agreement with related studies reported elsewhere [ 13 , 36 ]. The elemental mapping results of the UVS samples before and after adsorption is presented in Figure 4 .…”

“…The results revealed the morphology of the UVS featuring the laminar structure with some degree of surface roughness due to the deposited materials. The morphological characteristics (e.g., surface structure) of the UVS were similar to those of the absorbent shells reported in the other studies [ 36 , 37 , 38 ]. The dispersed tubular holes were also observed on the UVS surface.…”

Equilibrium, Kinetics and Thermodynamics of Chromium (VI) Adsorption on Inert Biomasses of Dioscorea rotundata and Elaeis guineensis

“…The stretched band at 1150 cm −1 is related to the stretching of the COO-anion, at 1080 cm −1 to the symmetric and asymmetric stretching of the C-O group of the ester vibration and at 1030 cm −1 to the functional group C-O-C [3]. The presence of hydroxyl groups, carbonyl groups, ethers and aromatic compounds is due to the high content of cellulose and lignin in the biomaterial; it is evidence of the lignocellulosic structure of the biomaterial under study, which contributes to the metal ion adsorption process [33].…”

Magnetic Fe3O4 Nanoparticle Biochar Derived from Pomelo Peel for Reactive Red 21 Adsorption from Aqueous Solution

“…Activated carbon is a commercial and frequently used adsorbent; however, it is of high cost [14,[20][21][22]. Recently, biosorbents derived from various kinds of biomass such as green coconut shell, clay, fly ash, sugarcane bagasse, mango kernel, coffee, and rice husk have been applied in many studies regarding the removal of various pollutants from an aqueous solution [23]. Biosorbents have been modified by various methods to enhance the adsorption capacity.…”