Abstract
This research explored the efficiency of snail shells powder (SSP) for Cu(II) removal from aqueous solutions and the production of valuable compounds from the residual product. To confirm its chemical and mineral components, the material was characterized by different instrumental techniques. The effects of experimental parameters such as the pH of the solution, the effect of SSP dose, particle size, and initial concentration of Cu(II) on the removal process were studied. The removal of Cu(II) was reasonably fast to be completed within a time frame of 90 min. The kinetics following the pseudo-second-order model (R2 = 0.979) were better compared to the pseudo-first-order model (R2 = 0.896). The increase in pH values leads to an increase in the amount of Cu(II) adsorbed. Afterward, the adsorption capacity reaches stability at pH near 7. The maximum Cu(II) removal occurred with a mass of 8 g·L−1 and a particle size of 300 μm. This particle size presents approximately 44.5% of SSP particles, which is the largest proportion of the sample as shown by particle size analysis. The adsorption isotherm was well described by Langmuir and Freundlich equations. The thermodynamic parameters values showed that the Cu(II) adsorption was a spontaneous and exothermic process. Furthermore, with the presence of CaCO3, the precipitation of Cu(II) in the form of posnjakite occurred with a high Cu(II) removal rate close to 99%. The residual SSP was used for the production of valuable compounds through the thermal decomposition process at various temperatures.
Highlights
Ey provide an harvested source of protein for local communities, discarding the shells as waste [22]. Using these shells as an adsorbent turns waste material into a potentially useful resource. e characterization of the product was carried out by using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), the point of zero charge, and X-ray diffraction analysis (DRX). e influence of pH of solutions, shells powder (SSP) dose, particle size, and initial Cu(II) concentration on the Cu(II) removal efficiency by SSP was studied through the batch method. e kinetic studies and mechanism adsorption between Cu(II) and SSP were discussed. e isotherm models and thermodynamic parameters were investigated. e production of valuable products in a single simple operation was examined
Adsorbent Material Preparation. e snail shells were collected from ambulant merchants in Fez, Morocco. ey were washed several times with tap water and ovendried at 80°C for 2 hours. e shells were crushed in an agate mortar; impurities such as the flesh were removed. ey were washed several times with distilled water and dried in an oven at 100°C for 12 hours. e above-dried shells were grounded to a fine powder. e resulting SSP was sieved through a range of sieves. e different resulting powders were collected and used for experimental purposes
SEM Analysis. e surface morphologies of SSP before and after the Cu(II) treatment are shown in Figure 1. e SEM images in Figure 1(a) indicate that the surface of SSP consists of condensed agglomerates made up of small particles
Summary
Ey were washed several times with tap water and ovendried at 80°C for 2 hours. Ey were washed several times with distilled water and dried in an oven at 100°C for 12 hours. E above-dried shells were grounded to a fine powder. E different resulting powders were collected and used for experimental purposes. E solutions of Cu(II) were prepared by dissolving 3.927 g of CuSO4.5H2O in deionized water (Barnstead EASYpure II) to achieve a concentration of 1000 mg·L−1. Experimental solutions of the desired concentrations of metal ions were prepared by diluting the stock solution in deionized water. E pH of the solutions was adjusted using 0.1 N HCl and 0.1 N NaOH to achieve a pH value ranging from 2 to 8; measurements were performed using a Hanna pH-meter model HI 2221. All reagents were AR-grade reagents obtained from Sigma-Aldrich Chemical Company
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