Linearized form effect on estimation adsorption parameters of three industrial dyes by lignocellulosic sorbent

Textile industries discharge large amounts of untreated colored wastewater into ecosystems which have adverse effects on the human, living and aquatic environment. The aims of this study were: upgrading and testing the brewery waste adsorption affinity towards BEMACID red (B-R), BEMACID yellow (B-Y) and BEZAKTIV black (B-B), verified the effect of linear form modeling on adsorption parameters values and to find the limiting kinetic step in adsorption process.

The adsorption efficiency of brewery waste towards three textile dyes: B-Y, B-R and B-B is tested. The evolution between the adsorption capacity and the operating conditions such as: pH solution, adsorbent mass, contact time and initial dye concentration is determined by kinetics measurements. Effect of a form of pseudo-first order, six forms of pseudo-second order, a form of intra-particle diffusion and a form of external mass transfer diffusion are tested to the prediction of kinetic parameters and to find the limiting kinetic step. In order to modeling the equilibrium data, a form of Freundlich and five forms of Langmuir isotherms are tested. The residual concentration of dye in solution was measured by spectrophotometer. Scanning Electron Microscope (SEM) was using to investigate the structure of raw adsorbent.

The results of kinetics measurements show that the perfect adsorption operating conditions are: acidic medium for all dyes (pH = 2 and pH = 3), low mass adsorbent (m = 40 mg), equilibrium time t = 40 min and for initial concentration of 250 mg/L. Also the results prove that the adsorption mechanism is controlled by both steps of diffusions (interne and extern diffusion) and fitted well by the first and the second linearized form of pseudo-second order model with correlation coefficient R² = 0.99. The results of isotherms modeling show that the second and the third linearized forms of Langmuir giving the best removed amount for B-Y equal 200 and 219.4 mg/g respectively compared to others linearized forms.

In summary, the effect of linear forms used either in the medellization of isotherms or kinetic data is significant in the prediction of adsorption parameters, also brewery waste has a significant B-Y dye adsorption affinity compared to others dyes, the descending order of maximum adsorption capacity finding is: qe = 209 mg/g for B-Y, qe = 152 mg/g for B-R and finally qe = 108 mg/g for B-B.