Due to their cost-effectiveness and high surface area, activated carbons are commonly used for the adsorption of dyes from aqueous solutions. In this study, activated carbon was synthesized from walnut shell waste via KOH activation (1:3 ratio), yielding a surface area of 2347.4 m²/g. Reactive Blue 19 and Reactive Red 195 adsorption behavior were studied under varying experimental conditions. These included natural pH values (6.8–7.2), dye concentrations between 50 and 1250 mg L⁻¹, and adsorbent dosages ranging from 0.1 to 1.0 g. Adsorption equilibrium was achieved within 150 min. The maximum adsorption capacities were found to be 1227.17 mg g⁻¹ for RB 19 and 235.74 mg g⁻¹ for RR 195. Isotherm modeling was conducted using Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models, with Freundlich providing the best fit for both dyes, indicating multilayer adsorption on heterogeneous surfaces. Thermodynamic analysis revealed that the adsorption processes were spontaneous and endothermic, with negative Gibbs free energy (ΔG°), positive enthalpy (ΔH°), and positive entropy (ΔS°) values. These results highlight the high adsorption performance and practical potential of walnut shell-derived activated carbon for dye removal from wastewater.

The separation and purification of important biomolecule deoxyribonucleic acid (DNA) molecules are extremely important. The adsorption technique among these methods is highly preferred as the adsorbent cryogels are pretty much used due to large pores and the associated flow channels. In this study, the adsorption of DNA via Co(II) immobilized poly(2-hydroxyethyl methacrylate-glycidyl methacrylate) [poly(HEMA-GMA)] cryogels was performed under varying conditions of pH, interaction time, initial DNA concentration, temperature, and ionic strength. For the characterization of cryogels; swelling test, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), surface area (BET), elemental and ICP-OES analysis were performed. L-lysine amino acid was chosen as Co(II)-chelating agent and the adsorption capacity of cryogels was determined as 33.81 mg DNA/g cryogel. Adsorption of pea DNA was studied under the optimum adsorption conditions and DNA adsorption capacity of cryogels was found as 10.14 mg DNA/g cryogel. The adsorption process was examined via Langmuir and Freundlich isotherm models and the Langmuir adsorption model was determined to be more appropriate for the DNA adsorption onto cryogels.

The separation and purification methods are extremely important for the hemoglobin (Hb) which is a crucial biomolecule. The adsorption technique is popular among these methods and the cryogels have been used quite much due to their macropores and interconnected flow channels. In this study, the Hb adsorption onto the Cu(II) immobilized poly(2-hydroxyethyl methacrylate-glycidyl methacrylate), poly(HEMA-GMA)-Cu(II), cryogels was investigated under different conditions (pH, interaction time, initial Hb concentration, temperature and ionic strength) to optimize adsorption conditions. The swelling test, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), surface area (BET), elemental and ICP-OES analysis were performed for the characterization of cryogels. Polyethyleneimine (PEI) molecule was used as a Cu(II)-chelating ligand. The Hb adsorption capacity of cryogels was determined as 193.8 mg Hb/g cryogel. The isolation of Hb from human blood was also studied under optimum adsorption conditions determined and the Hb (124.5 mg/g cryogel) was isolated. The adsorption model was investigated in the light of Langmuir and Freundlich adsorption isotherm models and it was determined to be more appropriate to the Langmuir adsorption isotherm model.

Magnetic microparticles have many applications in various areas today. The aim of this study was to develop hydrophobic magnetic microparticles as an alternative to traditional methods for high capacity and low cost removal of Victoria Blue R (VBR), which is valuable for industry and commercial, from wastewater and to determine the VBR adsorption ability of this adsorbent. Fe(II)–Co(II) double salt incorporated magnetic poly(2-hydroxyethyl methacrylate-N-methacryloyl-l-tryptophan) [m-poly(HEMA-MATrp)] microparticles were synthesized and used as adsorbent. These microparticles were synthesized in aqueous dispersion medium via microemulsion polymerization using MATrp and HEMA monomers. Magnetic hydrophobic microparticles were characterized via Fourier transform infrared spectroscopy, scanning electron microscopy, and vibrating sample magnetometer. Adsorption experiments were conducted for different conditions (pH, interaction time, amount of microparticles, temperature, and ionic strength) in batch system. VBR adsorption capacity of magnetic hydrophobic microparticles was estimated as 89.46 μmol/g. Adsorption–desorption cycles were repeated 4 times, and there was no significant decrease for the adsorption capacity observed.