Interpretations about methylene blue adsorption by surface modified chitin using the statistical physics treatment

Abstract

In this work, the adsorption of methylene blue (MB) on surface modified chitin (SMC) was studied at molecular level using the statistical physics theory. SMC adsorbent was prepared, characterized and applied for MB adsorption. Equilibrium curves were obtained at different temperatures (298, 308, 318 and 328 K) and interpreted by the statistical physics formulism. The parameters, such as, 'n' (number of adsorbed molecule(s) per site), 'N m ' (receptor site density) and 'c 1/2 ' (concentration at half saturation) were estimated and interpreted in detail. At finally, an interaction mechanism was proposed. The results revealed that the MB adsorption on SMC can be successfully represented by the statistical physics theory. The statistical physics parameters showed that the physicochemical interactions between MB and SMC are dependent of the temperature. At 298 K, the MB molecules were anchored by one or two receptor sites, in parallel to the SMC surface (probably hydroxyl and N-acetyl groups on the SMC surface). Otherwise, at 308, 318 and 328 K, the 'n' values higher than 1, indicated a perpendicular anchorage. List of symbolsARE Average relative error (%) BET Brunauer, Emmett and Teller method BJH Barrett, Joyner and Halenda method C 0 Initial dye concentration (mg/L) c Equilibrium dye concentration (mg/L) c 1/2 Concentration at half saturation (mg/L) FT-IR Fourier transform infrared spectroscopy k B Boltzmann constant (J/K) MB Methylene blue M a Adsorbed quantity (mg/g) M M nN m (mg/g) m M a /N a N a Number of adsorbed molecules N i Receptor site occupation state N m Receptor site density (mg/g) n Number of adsorbed molecules per site n 0 Anchorage number R 2 Coefficient of determination, dimensionless SEM Scanning electron microscopy SMC Surface modified chitin T Temperature (K) UA Ultrasound-assisted V Volume of solution (L) X Adsorbent amount (g) XRD X-ray diffraction Z gcGrand canonical partition functionGreek symbols b 1/k B T eReceptor site adsorption energy (kJ/mol) l Chemical potential (kJ/mol) k max Maximum wavelength of MB

Sorption Mechanism and Performance of Peat Soil Humin for Methylene Blue and <i>p</i>-Nitrophenol

“…7). This proposed mechanism of MB sorption on humin is in some extents similar with the proposed sorption mechanism of MB on an ultrasonically modified chitin [45]. It was claimed that the sorption of positively charged MB on the modified chitin at 298 K was governed by one or two receptor sites (probably hydroxyl and N-acetyl groups) on the modified chitin.…”

“…Further confusion appeared on the proposed structure of chitin [45] which contained more -CH3 group than the well accepted structure of chitin in literature, viz. Doğan et al [47] and Santosa et al [48].…”

“…The appearance of a new peak at ca. 1455 cm -1 as the C=C stretching vibration of the aromatic ring [45] must be contributed by MB and p-NP since they both contain an aromatic ring. In the case of the absorption band at ca.…”

“…If it is the case, every MB species needs more than one receptor site and consequently the value of n will be smaller than 1 not higher than 1. As MB is a relatively big in size (molar weight of 319.8 g/mol), it is hard to imagine that every receptor site on the modified chitin can bind more than one MB species to fulfil the value of n higher than 1 [45].…”

Physicochemical and thermodynamic study of malachite green adsorption on raw and modified corn straw

“…Statistical physics models can be developed based on the principle of grand canonical ensemble in statistical physics. From these models, it is possible elucidate the adsorption process at a molecular level based on the macroscopic properties of the involved materials . Furthermore, physicochemical parameters like number of molecules per site ( n ), adsorbed quantity at saturation ( Q asat ), density of the receptor sites ( N M ), and adsorption energies ( ϵ ) can be estimated .…”