Filtration and adsorption properties of porous calcium alginate membrane for methylene blue removal from water

Porous sodium alginate membrane was first prepared by vacuum freeze-dry method, then, sodium ions were substituted by calcium ions through cross-linking reaction to obtain the porous calcium alginate membrane via natural drying. The filtration and the adsorption properties of methylene blue on the porous calcium alginate membrane were studied through investigating the experimental parameters such as the pH, contact time, temperature and dosage. The data of the adsorption equilibrium were described by the Langmuir and Freundlich isotherms. The pseudo-first order, pseudo-second order, and intra-particle diffusion equation were used to evaluate the kinetic data. Thermodynamic analysis indicated that the adsorption of methylene blue on to the porous calcium alginate membrane was an exothermic reaction.