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.
Silica extracted from rice husk, which is represented as SRH, is inexpensive mesoporous silica useful for heavy metal removal from industrial waste effluents. SRH was synthesized through calcination at 650°C in an oxidant atmosphere obtaining a mesoporous silica with BET area of 297 m 2 g-1 and 2.3 nm of pore diameter average, respectively. The surface of this silica was modified through a post-synthesis route with amine and polyamine groups obtained at 16% and 47% of modified surface with amine or polyamine groups (SRH-NH 2 and SRH-triamine). The chromium(III) removal capacity of SRH and amine-modified silica was tested with stock solutions, observing a fast sorption process and reaching its equilibrium adsorption time in 20 min. The resulting Cr(III) removal capacity was 6.7, 22.1 and 34.3 mg g-1 for SRH, SRH-NH 2 and SRH-triamine silicas, respectively. SRH and SRH amine silicas were used to remove Cr(III) from a sample taken from a tannery waste effluent from the city of Leon, Guanajuato, Mexico, and displayed a 70% and 90% removal, respectively. Our results confirm the ability of these inexpensive silicas to adsorb materials and their potential use in heavy metals removal processes from industrial waste effluents.
Nowadays the contamination in waters by oily substances turns out to be a problem of world-wide scope and although some methods of removal of oils in water exist; these present some limitations; therefore, this project proposes the use of hydrophobic silicas as absorbent materials for oily substances. Modified silicas (R-SiO2) were synthesized using the Stöber method, modifying the surface by co-condensation. Tetraethyl-orthosilicate (TEOS) and two surface modifiers were used as silica former: Methyl-trimethoxysilane (MeTEOS) and n-octyl-triethoxysilane (nOctyl-TEOS). The R-SiO2 were characterized by infrared spectroscopy identifying the modifying groups and their hydrophobicity was qualitatively evaluated according to the change in solubility in water. Finally, the removability of an automotive motor oil was evaluated by determining the amount of oil removed per gram of modified silica.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.