Removal of lithium ions from aqueous solutions by an ultrafiltration membrane coupled to soluble functional polymer

Efficient removal of heavy metals in water utilizing facile cross-link conjugated linoleic acid micelles

Micellar-enhanced ultrafiltration (MEUF) technology is an effective method to treat low-concentration heavy metal wastewater. However, the leakage of surfactants in the ultrafiltration (UF) process will inevitably cause secondary pollution. In this study, a biosurfactant of conjugated linoleic acid (CLA) with conjugated double bonds was selected to bind its micelles by simple thermal crosslinking to obtain morphologically stable stearic acid (SA) nanoparticles. The pure SA nanoparticles were obtained by repeated dialysis. The stability of the SA nanoparticles was verified by comparing the particle size distribution and solubility of the materials before and after crosslinking at different pH levels. The effectiveness of SA nanoparticle-enhanced UF in removing heavy metals was verified by exploring the adsorption performance of SA nanoparticles. The dialysis device was used to simplify the UF device, wherein SA nanoparticles were assessed as adsorbents for the elimination of Cu2+, Pb2+, and Cd2+ ions from aqueous solutions under diverse process parameters, including pH, contact time, metal ion concentration, and coexisting ions. The findings indicate that the SA nanoparticles have no evidence of secondary contamination in UF and exhibit compatibility with a broad pH range and coexisting ions. The maximum adsorption capacities for Cu2+, Pb2+, and Cd2+ were determined to be 152.77, 403.56, and 271.46 mg/g, respectively.

Monitoring treatment of industrial wastewater using conventional methods and impedance spectroscopy

The main aim of this study was to develop and monitor an effective and cost-efficient industrial wastewater treatment system that utilizes sand, fly ash, and hearth ash. The latter two are potentially available and inexpensive industrial waste materials that can be used for filtration. The infiltration percolation method was utilized in a vertical cylindrical column to filter the raw wastewater from a detergent manufacturing plant. The main parameters analyzed before and after treatment included suspended solids (SS), chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), and pH. The system successfully achieved significant reductions, including 89% in COD, 73% in BOD₅, and 54% in suspended solids (SS), along with a 66% to 99% reduction in heavy metals. The COD/BOD₅ rejection ratio decreased from above 4.24 before treatment to below 1.73 after treatment. Furthermore, impedance measurements were carried out across the frequency range of 100 to 1 MHz. The analysis of complex conductivity spectra revealed two Cole-Cole relaxation behaviors, and an equivalent circuit was developed to extract the primary parameters and further investigate both relaxation processes. The results of the electrical parameters deduced from the impedance spectra demonstrated a strong correlation with the parameters obtained through conventional methods.

Chitosan- and Alginate-Based Hydrogels for the Adsorption of Anionic and Cationic Dyes from Water

Novel hydrogel systems based on polyacrylamide/chitosan (PAAM/chitosan) or polyacrylic acid/alginate (PAA/alginate) were prepared, characterized, and applied to reduce the concentrations of dyes in water. These hydrogels were synthetized via a semi-interpenetrating polymer network (semi-IPN) and then characterized by Fourier transformed infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), and their swelling capacities in water were measured. In the adsorption experiments, methylene blue (MB) was used as a cationic dye, and methyl orange (MO) was used as an anionic dye. The study was carried out using a successive batch method for the dye absorption process and an equilibrium system to investigate the adsorption of MO on PAAM/chitosan hydrogels and MB on PAA/alginate in separate experiments. The results showed that the target hydrogels were synthetized with high yield (more than 90%). The chemical structure of the hydrogels was corroborated by FTIR, and their high thermal stability was verified by TGA. The absorption of the MO dye was higher at pH 3.0 using PAAM/chitosan, and it had the ability to remove 43% of MO within 10 min using 0.05 g of hydrogel. The presence of interfering salts resulted in a 20–60% decrease in the absorption of MO. On the other hand, the absorption of the MB dye was higher at pH 8.5 using PAA/alginate, and it had the ability to remove 96% of MB within 10 min using 0.05 g of hydrogel, and its removal capacity was stable for interfering salts.