Kinetic study and thermodynamic equilibrium modeling of the Co(II) and Mn(II) bioadsorption using the Rhodococcus opacus strain

Microbial biomass is considered a renewable and environmentally friendly resource. Thus, the research conducted a kinetic study and thermodynamic equilibrium modeling of the cobalt (Co) and manganese (Mn) bioadsorption process using the Rhodococcus opacus (RO) strain as a biosorbent. The inactive biomass subjected to 0.1 M NaOH pretreatment was brought into contact with synthetic solutions of Co and Mn. The experimental data for the Co(II) and Mn(II) bioadsorption process were fit to the Langmuir model with kads of 0.65 and 0.11 L.mg-1, respectively. A better statistical fit was also obtained for the pseudo-second order kinetic model (R2Co(II) = 0.994 and R2Mn(II) = 0.995), with 72.3% Co(II) and 80% Mn(II) removals during the first 10 min. In addition, a higher affinity of RO for the Co(II) ion was observed, with maximum uptake values of 13.42 mg.g-1; however, a higher adsorption rate was observed for Mn(II) ion (k = 0.21 g.mg-1.min-1 at 318 K). The bioadsorption process was spontaneous and dependent on temperature, being endothermic and irreversible for the Co(II) ion (∆H = 2951.91 J.mol-1) and exothermic and reversible for the Mn(II) ion (∆H = -2974.8 J.mol-1). The kinetic and thermodynamic equilibrium modeling allowed to identify the main mechanisms involved in the biosorption process of both metals.Campus San Juan de Luriganch

Removal of Cr(VI) from mine effluents by ion exchange resins-comparative study of Amberlite IRA 400 And IRA 900

Strongly basic anion exchange resins, Amberlite IRA 400 and IRA 900, have been tested to remediate Cr (VI) from a model as well as from the untreated chromite mine effluent samples. For an initial concentration of 50 ppm Cr (VI), IRA 400 was found to adsorb Cr(VI) completely in less than 6 min of contact time and was efficient in a larger range of pH (1-6); however IRA 900 was able to remediate 97% Cr(VI) in the pH range 4.5-5 in less than 10 min. A cumulative loading of 112.9 mg/g and 115.2 mg/g of Cr(VI) was obtained with Amberlite IRA 400 and IRA 900, respectively from a feed of 200 ppm Cr(VI). A close adherence to the Freundlich isotherm during the adsorption reflected the strong chemical interaction of Cr6+ ions with the quaternary functional group on the resins. The adsorption process followed the pseudo-second-order kinetics. The experiments were further carried out in glass columns with 10 L chromite mine effluent samples. Almost complete sorption of Cr(VI) from the effluent was achieved using 0.5 % (w/v) IRA 400 and 2% (w/v) IRA 900, at a resin bed height of 7 cm and flow rate of 10 mL/min. Desorption studies in column show that 200-500 mL solutions of 15-30% (w/v) NaOH eluted the Cr(VI) completely from the metal-laden Amberlite IRA 400 and IRA 900 resins

Direct hematite flotation from an iron ore tailing using an innovative biosurfactant

The use of a biosurfactant (BS) in mineral flotation offers numerous advantages over conventional surfactants, such as their low toxicity, high degradation kinetics, and potential for selectively treating low-grade ores. In the present study, the use of a biosurfactant obtained from Rhodococcus opacus bacteria for the flotation of hematite from iron ore tailings was evaluated. The microflotation assessments were conducted in a modified Partridge-Smith cell, and the batch flotation studies were conducted in a mechanical cell (CDC - cell). In addition, the effects of the pH, biosurfactant concentration, and depressant concentration on hematite recovery were evaluated. The results confirmed the biosurfactant adsorption onto the hematite surface, and the biosurfactant decreased the surface tension of the water/gas interface. The critical micelle concentration (CMC) of the biosurfactant was approximately 1 g.L-1. Hematite recovery was feasible at a pH of around 3. In microflotation tests, the iron grade and recovery reached approximately 37% and 30%, respectively. These values increased in batch flotation circuits, specifically in the cleaner stage, the iron grade reached approximately 44% and the recovery was approximately 65%. Thus, the current development proved that this particular treatment of ore tailings carries environmental and technical benefits as an appropriate alternative cleaning technology