Modified kaolin clay (MKC) was synthesized through ultrasound-assisted coprecipitation method, and its adsorption behaviors to Cr(VI) and phosphate (P) from single and binary solutions were investigated by batch and column experiments. The adsorption capacities of Cr(VI) and P in single-ion solutions were found to be 309.60 and 605.75 mmol/kg, respectively. Because of competition adsorption, the adsorption capacities in binary solutions were reduced to 145.38 and 461.61 mmol/kg, respectively. The single and binary adsorption data fitted the pseudo-second-order kinetic model and the Langmuir isotherm well. The simultaneous addition of the two adsorbates led to a decrease and an increase in adsorption rate of Cr(VI) and P onto MKC, respectively. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy were performed to confirm the adsorption phenomenon. FTIR spectroscopy demonstrated that hydroxyl groups, NH 4 + , and NO 3 − ions on the adsorbent surface were responsible for Cr(VI) and P adsorption, and the adsorption mechanism involved anion exchange and surface complexation. Column experiments indicated that the breakthrough time and adsorption capacity of the fixed bed increased as the bed depth increased and decreased as the flow rate increased. The breakthrough curves were found to fit the Yoon−Nelson model well. Moreover, the feasibility of reusing MKC through three adsorption/desorption cycles in a fixed-bed column was studied. The column regeneration efficiency after the third cycle was 71.9% for Cr(VI) and 69.6% for P.

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After the successful preparation of empirical double network hydrogel beads from graphene oxide/sodium alginate(GO/SA), its cationic metal adsorption performance in aqueous solutions were investigated. Taking Mn(II) as an example, the contribution of several factors including pH, bead dosage, temperature, contact time and initial concentration ions to adsorption efficiency were examined. The Transmission Electron Microscopy (TEM) results indicate that the GO/SA double (GAD) network hydrogel bead strongly interpenetrate and the adsorption of Mn(II) is mainly influenced by solution pH, bead dose and temperature. The GAD beads exhibit an excellent adsorption capacity of 56.49 mg g−1. The adsorption process fit both Pseudo-second order kinetic model (R2 > 0.97) and the Freundlich adsorption isotherm (R2 > 0.99) and is spontaneous. After seven rounds of adsorption-desorption cycle, the adsorption capacity of GAD hydrogel remained unchanged at 18.11 mg/g.

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The adsorption of 1-naphthol (NAP) in aqueous solution was investigated using unmodified and modified diatomite at different temperature, pH, adsorbent mass and contact time. The adsorption capacity of the modified diatomite significantly improved (about 2 times at 298 K) compared to the unmodified diatomite. The adsorption showed a good fit with the Langmuir model. The further data analysis demonstrated that the adsorption of 1-NAP on both materials could be best described by the pseudo second-order kinetic model. The thermodynamic parameters, including Gibbs' free energy (∆G), enthalpy (∆H) and entropy changes (∆S) were determined. It was observed that the ∆H values (less than 40 kJ/mol) was positive, which indicated that the adsorption process is endothermic, physical adsorption. The ∆G values were negative, indicating that the adsorption of 1-NAP onto raw and modified adsorbent was spontaneous.