The ultramicropore biochar derived from waste distiller's grains for wet-process phosphoric acid purification: Removal performance and mechanisms of Cr(VI)

N-functionalized calcium alginate encapsulated with microalgae for efficient Pb removal: Mechanisms and performance in batch and column operations

In this study, a novel adsorbent called Ca@SP was developed by immobilizing microalgae protein (Spirulina platensis, SP) in an alginate matrix for enhanced Pb²⁺ removal from aqueous solutions. Synthesized via in situ crosslinking, Ca@SP leverages the synergistic effects of alginate's gel-forming ability and SP's N-rich biomass. Characterization of Ca@SP revealed a green spherical hydrogel with a BET specific surface area of 159.5 m²/g. The composite exhibited pH-dependent and highly selective adsorption for Pb²⁺ over other divalent metal ions, which can be explained by the relatively lower hydrated Gibbs free energy of Pb²⁺. The main adsorption mechanisms were identified as physical adsorption, electrostatic interaction, complexation, and ion exchange. Column experiments demonstrated Ca@SP's effectiveness under various operational conditions, including flow rate, influent concentration, and column heights. RSM was employed to optimize the adsorption process, with initial pH emerging as a critical parameter influencing Pb²⁺ removal efficiency. Desorption experiments showed that acidic solvents had higher desorption efficiency than alkaline solvents, and the potential for reusability was confirmed. These results suggest that Ca@SP has potential as an effective and sustainable adsorbent for Pb²⁺ removal from aqueous environments.

Non-Dispersive Extraction of Chromium(VI) by Cyphos IL102/Solvesso 100 Using the Pseudo-Emulsion-Based Strip Dispersion Membrane Operation

The removal of chromium(VI) from an acidic (HCl) medium through non-dispersive extraction with strip dispersion (NDXSD) was investigated using a microporous PVDF membrane support in a permeation cell. The ionic liquid Cyphos IL102 (phosphonium salt) in Solvesso 100 was used as an organic phase. In NDXSD, the stripping phase (NaOH) is dispersed in the organic phase on the cell side with an impeller stirrer adequate to form a strip dispersion. This pseudo-emulsion phase (organic + strip solutions) provides a constant supply of the Cyphos IL102/Solvesso 100 to the membrane phase. Various hydrodynamic and chemical parameters, such as variation in the feed and pseudo-emulsion stirring speeds, HCl and Cr(VI) concentrations in the feed phase, and carrier concentration, were investigated. Results indicated that the best chromium(VI) transport was obtained under the following conditions: feed and pseudo-emulsion stirring speeds of 1000 min-1 and 600 min-1, respectively; an HCl concentration in the feed phase of 0.1 M; a chromium concentration of 0.01 g/L in the same phase; and carrier concentration in the organic phase in the 2-5-10% v/v range. From the experimental data, several mass transfer coefficients were estimated: a bulk diffusion coefficient of 3.1·10-7 cm2/s and a diffusion coefficient of 6.1·10-8 cm2/s in the membrane phase and mass transfer coefficients in the feed (5.7·10-3 cm/s) and membrane phases (2.9·10-6 cm/s). The performance of the present system against other ionic liquids and the presence of base metals in the feed phase were investigated.

Hexavalent chromium ion removal from wastewater using novel nanocomposite based on the impregnation of zero-valent iron nanoparticles into polyurethane foam

In this study, we developed a novel nanocomposite, polyurethane foam impregnated with zero-valent iron nanoparticles (PU@nZVI), for the effective removal of chromium(VI) from various water sources. The characterization of nanocomposite (PU@nZVI) was performed by XRD, SEM-EDS, TEM and FT-IR techniques. Using the response surface methodology, we optimized the removal conditions, achieving an optimal pH of 2 and a dose of 0.5 g/L. The PU@nZVI demonstrated an excellent maximum adsorption capacity of 600.0 mg/g for Cr6+. The adsorption kinetics and isotherms were best described by the pseudo-second-order model and the Freundlich isotherm, respectively. Significantly, the nanocomposite removed 99.98% of Cr6+ from tap water, 96.81% from industrial effluent, and 94.57% from treated sewage wastewater. Furthermore, the PU@nZVI maintained its efficiency over five adsorption-desorption cycles, highlighting its reusability. These results suggest that the PU@nZVI nanocomposite is a highly efficient and sustainable option for chromium(VI) removal in water treatment applications.