Recently the interest in the remediation of liquid effluents from industries such as paint manufacturing, leather tanning, etc. has increased, because the quality of the water used in these processes is highly compromised and is generally discarded without any process of purification, causing an inadequate use of water and contributing to the hydric stress of the planet. Therefore, it is necessary to find alternatives for the remediation of water used in industrial processes; one of the methods that has been widely accepted given its high efficiency, low cost, and versatility compared to others is the bioadsorption using materials derived from various processes used for the elimination of metals such as Cr, Co, Cu, Ni, etc. from liquid effluents. Among the materials used for this purpose are rice husk, orange, and wheat as well as apatite (hydroxyapatite and brushite), derived from animal bones, which have shown good capacity (>90%) to adsorb metals from aqueous solutions. Through the characterization by DRX, FTIR, and SEM, of the brushite and studies in equilibrium and kinetics of adsorption, it has been demonstrated that this material has a good capacity to remove metals present in water.
Bioremediation is a pollutant removal method that has had a great boom due to the diversity of agroindustrial waste that can be used for this purpose, and that has shown having great efficiency and profitability in the adsorption of heavy metals, such as Pb, Cu, and Co. Based on the above, the present work carried out kinetic and equilibrium studies of bioadsorption of Cr (III) using orange peel (OP) as adsorbent, previously treated with methanol, water, and a water–methanol mixture at different pH (0.91, 1.78 and 2.72), and at 30 °C, finding that the adsorption capacity at equilibrium increases with increasing pH, having a maximum of 55 mg g−1 at pH 2.72—under these conditions, lower adsorption energy was used to remove Cr (III). In addition, it was determined that there are no external mass transfer limitations. An isoelectric point analysis indicated that the adsorption is not carried out by electrostatic forces and a FTIR study of the functional groups of OP showed a decrease in the main functional groups (pectin, cellulose, and lignin, among others), which is directly related to the adsorption capacity of the bioadsorbent.
a b s t r a c tNatural brushite (nDCPD) obtained from bovine bone was used to remove Cr(III) from aqueous solutions. Cr(III) adsorption was performed, varying adsorbent concentration and contact time in solution. The kinetic study of Cr(III) adsorption was performed with the kinetic models of pseudo-first order and pseudo-second order, Elovich, intraparticle and external diffusions. The experimental data were examined with the Langmuir, Freundlich, Redlich-Peterson (R-P), SIPS and Temkin isothermal models. The surface of the adsorbent was characterized by various techniques. The results show that most of the kinetic adsorption data were well described by the pseudo-first-order model, the equilibrium data were best fitted to the SIPS and Langmuir models, with adsorption capacity of 43.378 and 50.767 mg/g, respectively. The equilibrium time of the system was set at 10 h. A 95% Cr(III) removal rate was achieved. The calculated thermodynamic parameters show that Cr(III) adsorption is carried out spontaneously on the surface of nDCPD, although it is positively charged, indicating that nDCPD can be a low cost and easy to obtain effective adsorbent for the removal of Cr(III) from aqueous solutions.
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