The adsorption performance of carboxymethylcellulose-chitosan modified magnetic alkaline Ca-bentonite (MACB/C-C) was systematically evaluated under diverse environmental conditions to determine its efficiency in removing Pb(II) and Cd(II) from aqueous solutions. Batch experiments were conducted to assess the influence of initial pH, contact time, metal ion concentration, and temperature on adsorption capacity. The results demonstrated that pH plays a pivotal role in determining both the surface charge of MACB/C-C and the speciation of metal ions. As shown in Figure 9, removal efficiency increased sharply with rising pH, reaching a maximum at pH 5.0 for both Pb(II) and Cd(II). Below pH 2.0, adsorption dropped to near zero due to protonation of amino (–NH₂ → –NH₃⁺) and hydroxyl (–OH → –OH₂⁺) groups, resulting in electrostatic repulsion between positively charged adsorbent surfaces and cationic metal species. Above pH 5, deprotonation of –COOH to –COO⁻ and partial deprotonation of –NH₃⁺ enhanced ligand availability, promoting complexation and precipitation.
Kinetic studies revealed that the adsorption process was rapid initially, with equilibrium achieved within 3 hours. For MACB/C-C, the uptake of Pb(II) reached 95% of its maximum capacity within 1 hour, while Cd(II) required slightly longer—about 1.5 hours—due to lower diffusion rates and weaker coordination strength.L-Ascorbic acid web Pseudo-second-order kinetic modeling provided excellent fit (R² > 0.Oxazole-4-carboxylic acid Purity & Documentation 99), indicating chemically rate-controlled adsorption involving valence forces through sharing or exchange of electrons. Intra-particle diffusion analysis indicated multi-stage adsorption: an initial fast phase attributed to surface adsorption, followed by gradual diffusion into the porous structure, and finally a plateau representing equilibrium. The presence of the C-C film slightly slowed the diffusion rate but significantly improved structural stability.
Adsorption isotherms were analyzed using Langmuir and Freundlich models. The Langmuir model fitted the data better (R² > 0.PMID:34966099 99), suggesting monolayer adsorption on homogeneous sites. The maximum adsorption capacities (qmax) were determined as 483 mg·g⁻¹ for Pb(II) and 123 mg·g⁻¹ for Cd(II) at 25 °C, surpassing most reported adsorbents including zeolites, activated carbon, and other clay-based composites. These high values are attributed to the synergistic effect of abundant functional groups from ACB and the C-C coating, along with effective dispersion of Fe₃O₄ nanoparticles.
Temperature effects showed that adsorption increased with rising temperature (from 25 to 45 °C), indicating an endothermic process. Thermodynamic parameters calculated from van’t Hoff plots revealed negative ΔG values, positive ΔH (18.7 kJ·mol⁻¹ for Pb(II), 21.3 kJ·mol⁻¹ for Cd(II)), and positive ΔS, confirming spontaneous and entropy-driven adsorption. This suggests that chemical interactions dominate the mechanism. Furthermore, in the presence of common coexisting ions such as Zn²⁺, Cu²⁺, Na⁺, and K⁺, MACB/C-C maintained high selectivity for Pb(II) and Cd(II), demonstrating robustness in real-world applications. Overall, these findings confirm that MACB/C-C performs exceptionally well across a wide range of operational conditions, making it a highly reliable and adaptable material for heavy metal remediation.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com