Abstract:
The potential of waste residue obtained from alum manufacturing process to
remove problematic reactive azo dye (Cibacron brilliant red 3B-A) was
investigated. Batch adsorption experiments were carried out to find out the effects
of contact times, adsorbent doses, initial dye concentrations, and final pH on the
adsorption of the dye by both unmodified and neutralized adsorbents. The results
of the experiment showed that from initial dye concentration of 50 mg/L, the
adsorption of dye was rapid in the first 15 and 30 minutes of contact time and
equilibrium is reached in about 90 and 120 minutes for both unmodified and
neutralized adsorbents, respectively. About 92% the dye was removed by
unmodified adsorbent at its equilibrium contact time and optimum dose of 12 g/L,
however, only 68% removal efficiency was obtained for neutralized adsorbent at its
equilibrium contact time and optimum dose of 15 g/L. The time required to reach
equilibrium is independent of initial dye concentrations in the working range of this
experiment. For the neutralized adsorbent, the percentage of dye removal is nearly
constant in the initial pH range of 4-9, and the maximum removal of the dye was
obtained at initial pH of 3. In the case of unmodified adsorbent, maximum removal
of the dye was obtained at initial pH of 2. The equilibrium adsorption isotherms
have been examined by applying the Langmuir, Freundlich, Dubinin-
Rasdushkevich (D-R), and Temkin models. The experimental results can be best
described by the D-R isotherm. Adsorption kinetics of was analyzed using the
pseudo first and second order models and the regression results showed that the
adsorption kinetics were more accurately described by a pseudo second-order
model, moreover, the intra-particle diffusion was not the only rate limiting factor of
adsorption of the dye.
Key words: Cibacron brilliant red 3B-A, unmodified and neutralized adsorbents
adsorption isotherm, adsorption kinetics, and intra-particle diffusion.