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To describe the common behavior between the solutes and the adsorbent, adsorption isotherm is significant. It is also necessary for the design of the adsorption system (Zaman et al. 2021). In this study, Langmuir, Freundlich, Halsey, and Elovich models were used to determine the adsorption performance of Cr(VI) onto JSC. They not only give a basic idea of how effective the adsorbents are in removing Cr(VI) but they also describe the maximum quantity of Cr(VI) that the adsorbents can absorb. Figure 5 and Table 1 show the adsorption isotherms and computed values, respectively. The findings showed that the Freundlich (R2 = 0.995) and Halsey (R2 = 0.995) models suited the Cr(VI) adsorption onto JSC better than the Langmuir (R2 = 0.982) and Elovich (R2 = 0.974) models (Table 1). The multilayer adsorption process happens on a heterogeneous surface, according to the Freundlich and Halsey models. This lends credence to the theory that the JSC's surface is made up of tiny heterogeneous adsorption zones that are distinct in terms of adsorption phenomena. Because the value of n (2.327) in the Freundlich isotherm model was greater than 1, JSC was shown to be acceptable for Cr(VI) adsorption from an aqueous solution. The Langmuir model's separation factor values RL (0.154–0.018) are between 0 and 1, showing that the Cr(VI) adsorption procedure onto the JSC is appropriate, and the higher Kf value (3.499) also suggests that JSC readily uptakes Cr(VI) from the solution (Table 1).
Table 1

Isotherm parameters for Cr(VI) adsorption on JSC

ModelsParametersValues
Langmuir qmax (mg/g) 11.429 
b (L/mg) 0.550 
RL 0.154–0.018 
R2 0.982 
Freundlich Kf (mg/g) 3.499 
n 2.327 
R2 0.995 
Elovich qm (mg/g) 3.310 
Ke 2.241 
R2 0.974 
Halsey nH 2.327 
KH 18.45 
R2 0.995 
ModelsParametersValues
Langmuir qmax (mg/g) 11.429 
b (L/mg) 0.550 
RL 0.154–0.018 
R2 0.982 
Freundlich Kf (mg/g) 3.499 
n 2.327 
R2 0.995 
Elovich qm (mg/g) 3.310 
Ke 2.241 
R2 0.974 
Halsey nH 2.327 
KH 18.45 
R2 0.995 
Figure 5

Adsorption isotherm of Cr(VI) onto JSC using different isotherm models: (a) Langmuir isotherm, (b) Freundlich isotherm, (c) Elovich isotherm, and (d) Halsey isotherm.

Figure 5

Adsorption isotherm of Cr(VI) onto JSC using different isotherm models: (a) Langmuir isotherm, (b) Freundlich isotherm, (c) Elovich isotherm, and (d) Halsey isotherm.

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