Abstract
In this study, adsorption of Congo red dye onto activated carbon prepared from Jujube (Ziziphus Mauritiania) seeds with phosphoric acid as the activating agent was investigated. Batch adsorption studies were carried out to study the influence of contact time, adsorbent dosage and initial dye concentration on the adsorption. The data was analysed using pseudo-first order and pseudo-second order kinetic models. The pseudo-second order kinetic model was found to describe the adsorption more effectively with a perfect correlation coefficient of unity. The rate constant, K was obtained as 0.182 (g/mg min) and the calculated qe (9.81) is very close to the experimental value (9.78). A high correlation coefficient obtained when the data was analysed with the intraparticle diffusion rate equation, revealed the presence of intraparticle diffusion in the adsorption process even though it is not the sole controlling step as shown by the value of the intercept (C ≠ 0). Isotherm studies showed that there is high correlation in each case when the data was modelled with Langmuir, Freundlich, Temkin and Dubinin-Radushkevic isotherm models but the best fit was obtained with the Freundlich model with R2 = 0.9991, adsorption capacity, KF = 19.73 (mg/g)(mg/L)1/n and n = 1.563 indicating the adsorption is favourable and occurs on a heterogeneous surface by multilayer. The study showed that activated carbon from jujube seeds is an effective adsorbent for the removal of Congo red dye from solution.
Highlights
Isotherm studies showed that there is high correlation in each case when the data was modelled with Langmuir, Freundlich, Temkin and Dubinin-Radushkevic isotherm models but the best fit was obtained with the Freundlich model with R2 = 0.9991, adsorption capacity, KF = 19.73(mg/L)1/n and n = 1.563 indicating the adsorption is favourable and occurs on a heterogeneous surface by multilayer
Activated carbon was prepared from Jujube seeds via the chemical method using phosphoric acid as the activating agent
The amount of dye uptake and the percentage removal of the dye by the activated carbon are affected by the contact time, activated carbon dosage and the initial dye concentration
Summary
Colored organic effluent is produced in industries such as textiles, rubber, paper, plastic, cosmetics, etc. Some of these coloring materials have been reported to be carcinogenic and mutagenic to aquatic organisms [1]. They are difficult to remove because they are not degradable and are highly persistent in the environment [2]. As little as 1 ppm of dyes in water is highly visible, undesirable and toxic which make its removal before discharge into water bodies. Congo red which is an anionic dye widely used in textiles, paper, rubber, and plastic industries. Its removal from wastewater before being discharged into water bodies is imperative from both health and environmental point of view
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