Removal of some nitrophenol contaminants using alginate gel beads

Biopolymers such as alginates are commonly used to remove the cationic contaminants from wastewaters. The major component of the alginate is the alginic acid, a linear, binary heteropolymer of β-d-mannuronate and α-l-guluronate residues. In this study the fundamental aspects in the preparation of alginate beads and the effects of salt, sodium alginate concentrations and two cationic surfactants (dodecyltrimethylammonium bromide, cetyltrimethylammonium bromide) on the domains of binding isotherms were investigated. The alginate cross-link complexes with metal ions can exist either as homogeneous clear solutions or precipitates or as spherical beads. The applicability of the calcium and calcium–iron alginate gel beads for removal of some nitrophenols from aqueous solutions was studied. The sorption and kinetic experiments were conducted under different values of pH, initial concentration of nitrophenols and the amount of alginate gel beads. The removal efficiency of contaminant increases with the increasing of the pH and the quantity of alginate beads and decreases with the increasing of initial contaminant concentration. The uptake of nitrophenols occurs rapidly in the first 12 h, followed by a slow process that takes about 72 h. According to the egg-box model of gelation mechanism the cavities formed in the alginate gel capture the cationic contaminants. The adsorption equilibrium data obtained for nitrophenols derivatives at various pH and initial solid sorbent amount were applied to the two classical models, i.e. Langmuir and Freundlich, and the isotherm parameters were calculated.