Journal of Applied Chemical Science International

Residual dyes of textile dyeing effluents are dangerous to environment if directly disposed without proper treatments. Heavy metal complex dyes, such as Isolan Dark Blue 2SGL-01 (IDB), in particular are very difficult to bioremediated that must be removed before their disposal to water body. Layered double hydroxides (LDHs) are widely accepted adsorbents for anionic hazards. The adsorption of IDB was studied on the newly reported (CO₃)_0.26/Cl_0.48-Mg_2.67Zn_0.54Al layered double hydroxide (LDH20) from aqueous solutions. The adsorption parameters; initial pH, equilibration time, dosage of adsorbent and concentration of IDB, were studied. Optimum pH for adsorption was at pH=4.6, time of shaking 6 h and adsorbent dosage ≥ 0.2% w/v enabling removal efficiency of 99.3% for 100 mg L^-1 of IDB. Pseudo-second order rate kinetics model was suggested for the adsorption process indicating a chemisorption mechanism. Langmuir-type adsorption isotherm model was also suggested with a high monolayer capacity of 94.5 mg g^-1 higher than that reported for many LDH adsorbents for sulfonated dyes.

The adsorbed IDB was recovered in a single-batch process from LDH20 with an elution efficiency of 53.6% using one mol L^-1 Na₂CO₃ at 50ºC, which confirms that it will not represent a secondary sludge waste upon application for IDB removal.