Recovery of cobalt from dilute aqueous solutions using activated carbon–alginate composite spheres impregnated with Cyanex 272

A liquid micro-extraction based one-step method for the chemical fractionation of copper in seawater

In this work, the reagent Cyanex® 272 has been incorporated in a three-phase solvent bar micro-extraction system to selectively separate the inorganic and organic fractions of copper in seawater. Optimized conditions for micro-extraction of Cu fractions were 0.2 M Cyanex® 272 in the organic solution contained into the fiber pores, 0.5 M HCl as acceptor solution within the fiber, stirring rate of 500 rpm, and 60 min time of extraction, providing an enrichment factor of 51.6 ± 2.3. Experimental results for selective extraction of organic and inorganic Cu showed a good correlation with theoretical data for Cu speciation, and the relationship between enrichment factor and dissolved organic carbon (DOC) concentration in the samples was used to predict total Cu concentration. Instrumental determination of Cu presented a linear response within the range 0.1-20 µg L^-1, obtaining a limit of detection of 0.03 µg L^-1. Finally, the method was successfully applied to the study of Cu fractions in real seawater samples collected from the Bay of Cádiz (Spain).

Methylene blue contaminated water sanitization with alginate/compact discs waste-derived activated carbon composite beads: Adsorption studies

The adsorption behavior of different adsorbents has been studied by various research works. But few studies have compared linear and non-linear isotherm and kinetic models alongside phenomenological coefficients. Here, the effect of activated carbon black (ACB) on the methylene blue adsorption behavior of alginate was examined. A low-cost and green adsorbent was fabricated to can easily be detached from water. For this aim waste compact discs were recycled for the preparation of ACB. Loading of 15 wt% ACB related to pure alginate increased removal yield of alginate significantly. Isotherms and kinetic models in linear and non-linear forms were studied and the results were examined by comparing R² along with different error function values to find the best fitting. The results were well matched with non-linear pseudo-second-order and linear Langmuir. Intraparticle diffusion model and phenomenological coefficients represented control of adsorption by film diffusion and its limiting by pore diffusion.

Sorption capacity of seaweed-like sodium titanate mats for Co2+ removal

The development of new technologies for securing and recycling water resources are in high demand. A key focus of these technologies is the development of various ion exchangers or adsorbents that are used for the purification of aqueous solutions. Layered sodium titanate is one of the cation exchangers utilised in the removal of heavy metals and radionuclides from wastewater. To enhance the removal efficiency, the precise design of the crystal morphology, structure, and chemical composition is important. Herein, we synthesised a unique seaweed-like sodium titanate mat (SST) using a template-free alkaline hydrothermal process. The Co²⁺ sorption capacity of SST was investigated by batch testing with cobalt(ii) nitrate. SST, which was synthesised from titanium sulphate in a 10 M NaOH solution at 200 °C, had a seaweed-like structure composed of randomly distributed nanofibres of layered sodium titanate that is approximately 9 nm in diameter. The crystal shape changed from roundish crystals to fibrous crystals as the hydrothermal reaction period increased. The Co²⁺ sorption isotherm of SST was fitted with the Langmuir isotherm model and the maximum sorption density was 1.85 mmol g⁻¹. The selectivity of the Co²⁺ sorption on SST was high in comparison to that of Ca²⁺ and Mg²⁺. Herein, the Co²⁺ sorption mechanisms of SST were studied in comparison with commercially available sodium titanate. Results show that controlling the crystal morphology, structure, and Na concentration of the layered titanate that can be ion-exchanged determines the cation sorption properties of sodium titanate.

The seaweed-like sodium titanate mat has a high Co²⁺ sorption capacity via the ion-exchange reaction due to its crystal structure, low crystallinity, and morphology.