Removal Mechanisms of Toluene from Aqueous Solutions by Chitin and Chitosan

Abstract

Low-cost materials of natural origin such as chitin and chitosan were found to effectively remove toluene from aqueous solutions. Batch adsorption experiments for the removal of toluene (5–200 mg/L) were conducted to obtain the isotherm profile. The effects of various parameters such as initial concentrations, adsorbent dose, and contact time on the removal performance of toluene were evaluated. Chitosan shows better removal efficiency, compared to chitin, both in terms of the level of toluene adsorbed per unit mass of adsorbent and in terms of the adsorption kinetics. Adsorption capacity in the range of 33%–58% efficiency was obtained when the chitosan materials were used. The adsorption data on toluene were found to best fit the Langmuir and Redlich–Peterson isotherm models. The kinetic studies revealed that the adsorption of toluene followed the pseudo-second-order rate model. Overall, the study demonstrated that chitosan is a potential adsorbent for the removal of toluene at concentrations as high as 200 mg/L

Adsorption of toluene into commercial organoclay in liquid phase: Kinetics, equilibrium and thermodynamics

“…The adsorption of toluene onto commercial organoclay was well described by mass transfer in external film model and MSAM isotherm model at 288.15 K, D‐R isotherm model at 298.15 K and Sips isotherm model at 308.15 K. Thermodynamic study showed that toluene adsorption onto the adsorbent was physical, endothermic, and spontaneous. Due to its low cost, non‐toxicity, and adsorption capacity, this adsorbent can be considered one of the effective options to remove toluene from aqueous solutions, especially when compared to other adsorbents such as composite poly(4‐vinylpyridinium)‐maghnite and Chitin‐ and Chitosan‐based adsorbents …”

“…Due to its low cost, non-toxicity, and adsorption capacity, this adsorbent can be considered one of the effective options to remove toluene from aqueous solutions, especially when compared to other adsorbents such as composite poly(4-vinylpyridinium)-maghnite [48] and Chitin-and Chitosan-based adsorbents. [52] concentration of the solute in the initial solution (mmol/L) D intraparticle diffusion coefficient was radial coordinate related to particle size (cm 2 /s) D i effective diffusion coefficient (cm 2 /s) _ D parameter of heterogeneity d pore pore diameter (nm) E variation of free energy of adsorption (kJ/mol) F fraction of solute adsorbed at any time t h initial adsorption rate (mmol/g • min) k constant related to the D-R model (mol 2 /kJ 2 ) k 1 pseudo-first order rate constant of adsorption (min À1 ) k 2 second order rate constant (g/mmol.min) K TM mass transfer coefficient of liquid phase (h À1 ) K 1 constant that expresses the interaction between the solute and the type of site (L/mmol) K 2 constant that expresses the interaction between the solute and the type of site (L/mmol) K L constant of the equilibrium of the Langmuir equation and depends on the affinity between adsorbent and adsorbate (L/g) K 1 à constant that expresses the interaction between adsorbate and adsorbent in regions I (L/mmol) K 2 à constant that expresses the interaction between adsorbate and adsorbent in regions II (L/mmol) K F constant of the Freundlich equation (L/mmol) K dif intraparticle diffusion coefficient (mmol/g.min 0.5 ) number of points used n s parameters correspond to the parameters n of the Freundlich model n à number of points of the isotherm q e amount of toluene adsorbed at equilibrium (mmol/g) q e exp experimental adsorption capacity (mmol/g) q t amount of toluene adsorbed (mmol/g) at time t (min) q m maximum uptake capacity (mmol/g) q i cal adsorbed amount at equilibrium calculated by the model at each point of the curve i (mmol/g) q i exp equilibrium amount adsorbed on the experimentally measured (mmol/g), for each i point of the curve (mmol/g) q 1m maximum adsorption capacities of site 1 (mol/g) q 2m maximum adsorption capacities of site 2 (mol/g) q s parameter of Langmuir model (mmol/g) q m1…”

“…The Spectrogel commercial organoclay presented promising results for toluene removal when compared to other alternative adsorbents such as the composite poly(4-vinylpyridinium)maghnite studied by Zenasni et al [48] which showed q max of 5.86 mg/g (0.06 mmol/g), and Chitin-and Chitosan-based adsorbents studied by Mohamed and Ouki, [52] which presented q max of 2.5 mg/g (0.03 mmol/g) and took 8 h to reach equilibrium, while the organoclay study showed q max of approximately 0.27 mmol/g and less than 3 h for equilibrium.…”

Highly selective removal of organic dyes from aqueous solutions with chitin beads entrapping rectorite

“…The use of chitin as a carrier material for rectorite has enlightened the possibility of having a selective adsorption of organic molecules; this depends on their electrical charge because of interactions with the hydroxyl and acetyl amino groups on chitin. Chitin can accumulate metal ions and organic dyes; this gives it potential applications in dealing with wastewater containing toxic components . Some work has been done to adapt this promising material to industrial fluidized bed processes .…”

“…Chitin can accumulate metal ions and organic dyes; this gives it potential applications in dealing with wastewater containing toxic components. [22][23][24] Some work has been done to adapt this promising material to industrial fluidized bed processes. 25,26 Chitin is a linear polysaccharide composed of b-(1-4)-linked 2-acetamido-2-deoxy-Dglucose units.…”