Adsorption of Methylene Blue from Aqueous Solution onto a Low-Cost Natural Jordanian Tripoli
Titel:
Adsorption of Methylene Blue from Aqueous Solution onto a Low-Cost Natural Jordanian Tripoli
Auteur:
Atef S. ALzaydien
Verschenen in:
American journal of environmental sciences
Paginering:
Jaargang 5 (2009) nr. 3 pagina's 197-208
Jaar:
2009
Inhoud:
Background: Dyes and pigments are widely used, mostly in the textiles, paper, plastics, leather, food and cosmetic industry to color products. The release of colored wastewater from these industries may present an eco-toxic hazard. Various techniques like precipitation, ion exchange, chemical oxidation, and adsorption have been used for the removal of toxic pollutant from, wastewater. Methylene blue (MB) is selected as a model compound for evaluating the potential of tripoli to remove dye from wastewaters. Objective: In this study, Jordanian low- cost locally available tripoli was studied for its potential use as an adsorbent for removal of a cationic dye (methylene blue,MB) from aqueous solution. Factors affecting adsorption, such as , initial dye concentration, pH, contact time , adsorbent dose and temperature, were evaluated. The equilibrium of adsorption was modelled by using the Langmuir , Freundlich, Temkin and Dubinin-Radushkevich isotherm models, the kinetic parameters and intraparticle diffusion were also then determined for the methylene blue-tripoli system. Methodology: The raw tripoli samples were kindly supplied by the Authority of Natural Resources (Jordan, Amman). X-ray diffraction spectroscopy (XRD) analysis was carried out with PANalytical X-ray, Philips Analytical. Fourier transform infrared spectrophotometry (FT-IR) analysis was conducted. The cation exchange capacity (CEC) of tripoli was estimated using The copper bis-ethylenediamine complex method. The specific surface area of tripoli was estimated using Sears’ method by agitating 1.5 g of the tripoli sample in 100 ml of diluted hydrochloric acid of a pH = 3. Adsorption equilibrium studies were carried out by adding 0.5 g of tripoli in a series of 250mL flasks containing 100mL of MB solution of different dye concentrations at four different temperatures (20, 30, and 50 ◦C). The experiments of adsorption kinetics were carried out in stirred batch mode. For each experiment, 0.1 L of the MB dye solution at specified concentrations was continuously stirred at 160 rpm with 0.5 g of Tripoli at 25◦C. Samples were withdrawn at appropriate time intervals and then centrifuged at 4000 rpm for 15 min and the absorbance of the supernatant was measured. The concentration of the residual dye was measured using UV/visible spectrometer at a λmax corresponding to the maximum absorption for the dye solution (λmax= 661 nm). Results: Four kinetic models are the pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion equations, were selected to interpret the adsorption data. The kinetic parameters were calculated from the experimental data and it was shown that they could be fitted well to the pseudo-second-order kinetic and intra-particle diffusion models. The linear Langmuir and Freundlich models were applied to describe equilibrium isotherms The adsorption data obtained were well described by the Langmuir adsorption isotherm model. The maximum adsorption capacity was found to be 16.6 mg g−1 from the Langmuir isotherm model at 25 ◦C. The Langmuir isotherm constant, KL, was used to evaluate the changes of free energy . The negative value of free energy change indicated the spontaneous nature of sorption and confirmed affinity of natural Jordanian tripoli for the methylene blue basic dye .Conclusion: The present study shows that the natural Jordanian tripoli, an abundant low-cost clay, can be used as sorbent for the removal of methylene blue dye from aqueous solutions. The amount of dye sorbed was found to vary with initial pH, tripoli dose, methylene blue concentration and contact time. The value of The monolayer saturation capacity of tripoli was comparable to the adsorption capacities of some other adsorbent materials for MB dye .
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