Adsorption of four dyes, namely methyl violet (MV), rhodamine 6G (R6G), acid chrome blue K (AK) and xylenol orange (XO) onto sodium alginate graft poly(acrylic acid-co-2-acrylamide-2-methyl-1-propanesulfonicacid)/kaolin (SA-g-P(AA-co-AMPS)/KL) hydrogel composite is studied. The factors influencing the adsorption capacities, including the initial concentrations of dye solutions, contact time, initial pH values and dosage of the adsorbent as well as ionic strength of the solution are discussed. It is more effective for the composite to adsorb cationic dyes such as MV and R6G rather than anionic dyes AK and XO. The maximum adsorption capacities of MV, R6G, AK and XO are 1361.1, 1627.8, 563.5 and 312.4 mg/g, respectively. The adsorption thermodynamics for the four dyes are in accordance with both the Freudlich and Redlich-Peterson equations. It is shown that adsorption of the cationic dyes R6G and MV is spontaneous, while that of anionic dyes AK and XO is not. The kinetics studies show that the adsorption of the four dyes fitted a pseudo-second-order equation.
Eco-friendly decolorization of cationic dyes by coagulation using natural coagulant Bentonite and biodegradable flocculant Sodium Alginate
