Isotherms, kinetic and thermodynamic studies of methylene blue adsorption on chitosan flakes derived from African giant snail shell

Abstract

In the present study, modeling of 19 adsorption isotherms, 8 kinetic models and thermodynamics of methylene blue (MB) adsorption on chitosan flakes synthesized using Archachatina marginata shell wastes was investigated in a batch mode. The operational parameters' effects on the MB adsorption were studied. The model parameters were statistically analyzed using 10 error functions. The choices of the best fitted adsorption and kinetic models were based on the comparison of the sum of normalized error (SNE) and two statistical tools of information-based criteria. The 5-p Fritz-Schlüender isotherm best fitted the experimental adsorption data of MB on chitosan flakes based on SNE whereby maximum adsorption capacity, ax m q , of 143.6660 mg/g was obtained. The adsorption rate of MB on chitosan flakes was kinetically described by pseudo second-order model at all initial concentrations of MB investigated, with film diffusion being the rate-controlling step and the adsorption process chemisorption-influenced. The calculated thermodynamic parameters, 0 H  = 4.23 kJ/mol, 0 S  = 0.4563 kJ/(mol K), negative 0 G  values revealed that the adsorption of MB onto chitosan flakes was physical, endothermic, spontaneous, energetically favorable and exergonic. The reaction mechanism of the adsorption of MB onto chitosan flakes was proposed taking cognizance of the electrostatic force of attraction between the negatively charged surface of the chitosan (biosorbent) and the positively charged MB.

Modelling the Adsorption of Arsenic from Water and Wastewater using Microsoft Excel Solver and SPSS

“…Table 7, which is ANOVA results for AIC revealed that there was no significant difference between the methods (MES and SPSS) at the 95 % confidence level (F 1,21 = 2.50; p =0.129), but between the adsorption isotherm models there were significant difference (F 21,21 = 6.80; p = 0.000). The results from these tables agree with the literature (Nameni et al, 2008;Wongcharee et al, 2017;2018;Henley et al, 2019;Jasper et al, 2020;Suwannahong et al, 2021;Olaosebikan et al, 2022), which highlighted that adsorption equilibrium isotherm models are significantly different in expressions and in magnitude.…”

Rapid adsorptive removal of eosin yellow and methyl orange using zeolite Y

“…These obvious trends support the notion that adsorption is advantageous at low and detrimental at high temperatures. This also implied an exothermic reaction corresponding to the estimated thermodynamic parameters 71 , 72 . The amount of EY and MO adsorbed reduced as the temperature increased, which has a negative effect on eosin yellow and methyl orange adsorption on zeolite Y, demonstrating an inverse link between temperature and percentage removal and adsorption capacity of the adsorption system 76 .…”

“…At 90 min, the percentage removal of MO and EY onto zeolite Y was 80%, 67%, 65%, 61%, and 62% for MO and 60%, 51.20%, 64.70%, 65.60%, and 61% for EY at concentrations of 20, 30, 40, 50, and 60 mg/L, respectively. The large percentage removal at low concentrations is due to the availability of more active adsorption sites on the zeolite with less MO and EY molecules to occupy, so the limited available MO and EY molecules were adsorbed rapidly 71 , 72 .…”

“…Figure 5 a,b shows that as the adsorbent dosage is increased, the adsorption capacity decreases. This is due to the active sites being exposed to a small quantity of adsorbent while a few fractions were exposed to a higher dose of the zeolite Y 72 , 74 . This will influence the increase in the percentage removal of the dyes (methyl orange and eosin yellow).…”