Equilibrium, Thermodynamic and Mechanism Studies of Malachite Green Adsorption on Used Black Tea Leaves from Acidic Solution

Abstract

This study reports the equilibrium adsorption mechanism and thermodynamics for the removal of Malachite Green (MG) from acidic solution using Used Black Tea Leaves (UBTL) as a low cost adsorbent. The effect of initial dye concentration, processing temperature and the presence of electrolytes on the adsorption from acidic solutions were investigated in batch process. Adsorption process was attained to the equilibrium at about 24 hours. Adsorption isotherms of MG on UBTL for different temperatures were constructed at pH 2.0 and the equilibrium adsorption data were analyzed using different model equations such as Langmuir, Freundlich, Temkin, Dubinin-Radushkevich (D-R), Harkin-Jura, Halsey, Elovich-Larionov and Flory-Huggens isotherms. The experimental results were reasonably correlated by Langmuir, Flory-Huggins and D-R models than other isotherm models. The maximum adsorption capacity (qm), intensity of adsorption (b) and separation factor (Rb) were calculated from Langmuir plot and activation energy of adsorption (Ead) was determined from D-R isotherm. At pH 2.0, the equilibrium adsorption capacity of UBTL to MG is 110 mg∙g-1 at 30°C, which was increased with increasing temperature suggested endothermic nature of adsorption. Thermodynamics parameters: ΔGads, ΔHads and ΔSads were calculated from Langmuir constant (b). The positive values of enthalpy and free energy, and negative value of entropy suggested that the adsorption is less spontaneous and surface migration or fragmentation of MG molecules on UBTL surface might be occur. Again, the low value of activation energy of adsorption (Ead = 0.3 kJ∙mol-1 <8 kJ∙mol-1) suggested that the adsorption is controlled by physical in nature. A possible mechanism involvement of protonation is proposed from the effect of electrolytes during the adsorption of MG on UBTL at pH 2.0.

A Review on Effects of Operating Parameters in Batch and Column Mode for Adsorption of Methyl Violet Dye

“…In some adsorption processes, equilibrium is not reached because column adsorption times are shorter than batch adsorption times [19,33,70]. Even if it's probable that column adsorption's reduced contact time may render the results of batch experiments inaccurate, they can still be used to predict performance [60].…”

“…This allows the dye to be utilized to its full potential [18]. Dye molecules created specifically for use in textiles are designed to build a strong bond with the fiber molecules to which they are applied [19]. Protein fibers are colored using acid, mordant, and vat dyes, while cellulose fibers are colored with direct, reactive, and vat dyes [20].…”

Adsorptive Potency of Activated Carbonized Avocado Pear Seeds (Persea Americana) and Activated Carbonized orange peels (Citrus Sinensis) in Eliminating Pb2+ ions in Contaminated Water.

“…Isotherm model of Dubinin-Radushkevich is unfounded on ideal assumptions for instance, steric encumbrance nonexistence in the middle of adsorbed and entering particles, equal efficacy of the adsorption locations and surface uniformity on microscopic level as in Langmuir isotherm (Sarı and Tuzen, 2009;Amin et al, 2015;Moftakhar et al, 2016). The Dubinin-Radushkevich equation (equation 5) has been broadly applied to expound energetic heterogeneousness of solid at low level coverage as one-tracklayer zones in micropores (Hossain et al, 2016;Inyinbor et al, 2016). Dubinin-Radushkevich isotherm is regularly applied to illustrate solo solute systems adsorption isotherms (Essomba et al, 2014).…”

Comparative Study of Adsorption of Methylene Blue and Basic Red 9 Using Rice Husks of Different Origins

“…Adsorption is an excellent method for removing dyes from wastewater because of its low processing cost and simple design [11]. Several studies have been conducted on the adsorption of cationic dyes using bio-adsorbents such as date seeds, orange peels, dragon fruit peels, spent Ganoderma lucidum substrates, black tea leaves, and wood apple shells [12][13][14][15][16][17]. These studies show that adsorption is an efficient and the most effective method for the removal of cationic dyes.…”