Adsorption of Cd (II) Ions by Coconut Copra: Isotherm and Regeneration Studies

Abstract

This study employed coconut copra to adsorb cadmium and investigated its adsorption behavior via isotherm models. A total of seven isotherm models, namely Langmuir, Freundlich, Sips, Temkin, Dubinin-Radushkevic, Brouers-Sotolongo and Hill were utilized to investigate the adsorption mechanism. Results showed that Langmuir isotherm best fitted cadmium adsorption process among all models studied, with correlation coefficient, R2 of 0.963. The maximum adsorption capacity of coconut copra towards cadmium recorded 1.092 mg g−1 according to Langmuir isotherm, Dubinin-Radushkevic and Temkin isotherm asserted that this is a physical adsorption process. This study however observed negative cooperativity, as claimed by Hill and Temkin isotherm models. In addition, this study explored the feasibility of biosorbent regeneration. Coconut copra demonstrated potential to be regenerated, supported by its efficient removal percentage up to 7 consecutive adsorption-desorption cycles. As a whole, coconut copra is potentially viable to be used as a sustainable biosorbent for cadmium removal cadmium.

Matrix-dispersed magnetic molecularly-imprinted polyaniline for the effective removal of chlorpyrifos pesticide from contaminated water

“…Values <8 kJ mol −1 indicate a weak interaction between the adsorbate and adsorbent molecules at the adsorbent surface. 73 The obtained b T value is about 677 whereas the B value was found to be 3.66 J mol −1 . These values were obtained from a linear plot between q e and ln C e with r 2 = 0.9718.…”

“…8c ) assumes that the heat of adsorption of all molecules in the layer decreases linearly as a result of increase in surface coverage. 73 The value of the constant b determines the type of the sorption process. When b T value is <80 000, this indicates physical adsorption.…”

Azo-functionalized superparamagnetic Fe3O4 nanoparticles: an efficient adsorbent for the removal of bromocresol green from contaminated water

“…The calculated n and K F values are 2.20 and 229.40, respectively, showing that the adsorption process is physisorption and BCG is preferentially adsorbed onto the ADFS surface. 61,62…”

“…The obtained b T value is about 200.26 whereas the B value is 12.37 J mol −1 and the correlation coefficient of the Temkin plot is 0.8809, indicating that the adsorption process is physisorption. 62–64 Based on the regression correlation coefficient values of the three isotherms, the Freundlich isotherm model is the best model that describes the adsorption of BCG onto the ADFS surface. According to the Freundlich model, the adsorption is a physisorption process.…”

“…The calculated n and K F values are 2.20 and 229.40, respectively, showing that the adsorption process is physisorption and BCG is preferentially adsorbed onto the ADFS surface. 61,62 The Langmuir isotherm is shown in Fig. 8E and the resulting values of q max , r 2 and b were 70.92 mg g À1 , 0.9121 and 0.09, respectively.…”