Decontamination of radioactive cesium ions using ordered mesoporous monetite.

We report herein the fabrication of an environmentally friendly, low-cost and efficient nanostructured mesoporous monetite plate-like mineral (CaHPO4) as an adsorbent for removal of radioactive cesium ions from aqueous solutions. The phase and textural features of the synthesized mesoporous monetite were well characterized by XRD, FTIR, SEM, HRTEM, DLS, TGA/TDA, and N2 adsorption/desorption techniques. The results indicate that the cesium ions were effectively adsorbed by the mesoporous monetite ion-exchanger (MMT-IEX) above pH 9.0. Different kinetic and isotherm models were applied to characterize the cesium adsorption process. The fabricated monetite exhibited a monolayer adsorption capacity up to 60.33 mg g-1 at pH of 9.5. The collected data revealed the higher ability of CaHPO4 for the removal of Cs(i) from aqueous media in an efficient way.

Cysteine-Functionalized Chitosan Magnetic Nano-Based Particles for the Recovery of Light and Heavy Rare Earth Metals: Uptake Kinetics and Sorption Isotherms.

Cysteine-functionalized chitosan magnetic nano-based particles were synthesized for the sorption of light and heavy rare earth (RE) metal ions (La(III), Nd(III) and Yb(III)). The structural, surface, and magnetic properties of nano-sized sorbent were investigated by elemental analysis, FTIR, XRD, TEM and VSM (vibrating sample magnetometry). Experimental data show that the pseudo second-order rate equation fits the kinetic profiles well, while sorption isotherms are described by the Langmuir model. Thermodynamic constants (ΔG°, ΔH°) demonstrate the spontaneous and endothermic nature of sorption. Yb(III) (heavy RE) was selectively sorbed while light RE metal ions La(III) and Nd(III) were concentrated/enriched in the solution. Cationic species RE(III) in aqueous solution can be adsorbed by the combination of chelating and anion-exchange mechanisms. The sorbent can be efficiently regenerated using acidified thiourea.

Fast removal of uranium from aqueous solutions using tetraethylenepentamine modified magnetic chitosan resin.

Chitosan was cross-linked using glutaraldehyde in the presence of magnetite. The resin was chemically modified through the reaction with tetraethylenepentamine (TEPA) to produce amine bearing chitosan. The resin showed a higher affinity towards the uptake of UO2(2+) ions from aqueous medium: maximum sorption capacity reached 1.8 mmol g(-1) at pH 4 and 25 °C. The nature of interaction of UO2(2+) ions with the resin was identified. Kinetics were carried out at different temperatures and thermodynamic parameters were evaluated. Breakthrough curves for the removal of UO2(2+) were studied at different flow rates, bed heights and after 3 regeneration cycles. Hydrochloric acid (0.5 M) was used for desorbing UO2(2+) from loaded resin: desorption yield as high as 98% was obtained.

Fast kinetic and efficient removal of As(V) from aqueous solution using anion exchange resins.

Glycidyl methacrylate/methelenebisacrylamide resin with immobilized tetraethylenepentamine ligand was prepared. This pentamine containing resin was transformed to two anion exchange resins through treatment by glycidyl trimethylammonium chloride to give (RI) or hydrochloric acid giving (RII). The resins were used to adsorb As(V) at different experimental conditions using batch and column methods. Kinetics and thermodynamic properties as well as the mechanism of interaction between As(V) and resin active sites were discussed. The maximum adsorption capacities of As(V) on RI and RII were found to be 1.83 and 1.12 mmol/g, respectively. The regeneration and the durability of the loaded resin towards the successive reuse were also investigated.

Effect of structural properties of acid dyes on their adsorption behaviour from aqueous solutions by amine modified silica.

Monoamine modified silica particles (MAMS) were prepared and characterized by infrared (FT-IR) and thermogravimetric analysis (TGA). The modified silica particles were used for removal of acid orange 10 (AO-10) and acid orange 12 (AO-12) from their aqueous solutions. The adsorption behaviour of the two dyes was studied at different experimental conditions of pH, contact time, concentration of dye, temperature and salt solution. The adsorption of AO-10 followed pseudo-first order kinetics whereas AO-12 followed pseudo-second order. The two dyes showed different modes of interaction with silica surface. Desorption of the loaded dyes was carried out at pH 10 and found to be 10.4 and 91.6% for AO-12 and AO-10, respectively.

Synthesis of magnetic chelating resins functionalized with tetraethylenepentamine for adsorption of molybdate anions from aqueous solutions.

Magnetic resins were synthesized through polymerization of glycidyl methacrylate (GMA) in the presence of divinylbenzene (DVB) or N,N'-methylenebisacrylamide (MBA) as hydrophobic or hydrophilic crosslinker, respectively and in presence of suspended magnetite particles. The resins containing (DVB or MBA) as crosslinker were immobilized with tetraethylenepentamine (TEP) to give the amino resins, GMA/DVB/TEP (R1-en) and GMA/MBA/TEP (R2-en), respectively. The uptake behavior of the two resins was studied towards molybdate anions and uptake capacities of 4.24 and 6.18 mmol/g [as (Mo(VI)] were obtained using (R1-en) and (R2-en). Kinetic studies showed that the adsorption followed the pseudo-second-order model pointing the influence of the textural properties of the resin on the rate of adsorption. Thermodynamic data indicated an endothermic adsorption process. The uptake of Mo(VI) and regeneration of the resins were also studied using the column method. Regeneration efficiency up to 90-96% was reached using ammonia buffer.

Selective separation of mercury(II) using magnetic chitosan resin modified with Schiff's base derived from thiourea and glutaraldehyde.

Magnetic chitosan resin was chemically modified by a Schiff's base cross-linker. The interaction of the resin obtained with Hg(II) was studied and uptake value of 2.8 mmol/g was reported. The kinetic and thermodynamic parameters of the adsorption process were estimated. These data indicated that the adsorption process is exothermic and follow the pseudo-second-order kinetics. The selectivity of Hg(II) from other different metal ions in solutions using the studied resin was also reported. Breakthrough curves for the recovery of Hg(II) were studied. The critical bed height was found to be 2.05 cm. The adsorbed Hg(II) was eluted from the resin effectively using 0.1 M potassium iodide.

Synthesis of a quaternary amine anion exchange resin and study [of] its adsorption behaviour for chromate oxyanions.

Glycidyl methacrylate/N,N'-methylene bis-acrylamide (GMA/MBA) was prepared and allowed to react with tetraethylenepentamine (TEP) to give glycidyl methacrylate amine resin (RPA) followed by treatment with glycidyl trimethylammonium chloride (GTA) to give glycidyl methacrylate resin bearing quaternary ammonium chloride moieties (RQA). Zeta potential measurements showed that RQA particles are positively charged over pH 2-10 indicating the strong basic nature of the quaternary amine sites. The effect of pH on the recovery of chromate by RPA and RQA was examined. The results indicated that RQA is an efficient sorbent for chromate from both acidic and basic media. The repeated use of RQA was tested through stripping the adsorbed chromate using a mixture of 0.05 NaOH and 2 M NaCl in the case of the uptake from acidic media and using 2 M NaCl solution in the case of alkaline solutions.