Search

A novel method of synthesis of spherical resorcinol–formaldehyde resin was developed, using calcium alginate beads as template. Batch sorption experiments were carried out, to remove cesium ions from aqueous alkaline solutions, using the synthesized resin beads. The effect of operating variables, such as the initial cesium ion concentration, sodium ion concentration, and contact time, on the sorption of cesium ions was studied. Equilibrium data were found to fit better to Langmuir isotherm equation, with a monolayer sorption capacity of 490.2 mg/g, and the complete elution of the sorbed cesium ions was also possible. Sorption data were also analyzed in terms of both Lagergren first-order and pseudo second-order kinetic models, and were found to follow pseudo second-order kinetics at lower initial cesium ion concentration. The kinetic parameters were determined at different initial concentrations. The process mechanism was found to be complex, consisting of both film diffusion and intraparticle diffusion. Sorption data were also analyzed, using a Boyd plot, which confirmed that the rate-limiting step is the film diffusion.

Mesoporous titanium dioxide microspheres were synthesized by the sol–gel templating method, using calcium alginate as a sacrificial template, and subjecting to different temperatures, under various atmospheres. The gradual changes in composition, crystallinity, phase and surface morphology, due to variation in calcination atmosphere and temperature, were monitored by TGA, XRD, SEM and EDX techniques. The effect of polymeric content on the surface area and the pore size of the titania beads was evaluated by BET analysis. The results show that N 2 atmosphere and high temperature influence the phase content and morphology of the microsphere significantly. Anatase to rutile phase transformation and formation of calcium titanate take place under nitrogen atmosphere at lower temperature, as compared to that under air atmosphere. To examine the applications of these synthesized microspheres, photo-catalytic activity and sorption efficiency of the microspheres were evaluated, by carrying out photo-degradation of methylene blue (MB) dye, and removal of arsenic ions from ammoniacal solution. The microspheres showed good photo catalytic activity towards MB dye. Tracer experiments with 76 As showed ∼98% sorption of arsenic ions from aqueous solution onto the titania microspheres.