Fluoride removal from aqueous solution via environmentally friendly adsorbent derived from seashell

Abstract

Nowadays, the presence of excessive ions in water resources is of utmost concern and has attracted increasing attention; therefore, excessive amounts of these ions such as fluoride should be removed from drinking water. Conventional water treatment processes are shown to be incapable of the complete removal of redundant fluoride from aqueous water bodies, whereas adsorption is a promising, effective, cost–benefit, and simple method for this purpose. This study aimed to synthesize effective adsorbents from bivalve shells and evaluate the adsorption function of bivalve shells in removing fluoride from aqueous solutions. In this study, the oyster shell was collected from the Persian Gulf’s seaside and were crushed by manual mortar and blender, and graded with standard sieves with 70 mesh size. The prepared bivalve shell was characterized by SEM and FTIR. To investigate and optimize various variables on fluoride removal percentage a response surface methodology based on central composite design (RSM-CCD) was used. Under optimal conditions (pH: 5.5, adsorbent dose: 0.3 g/L, contact time: 85 min and fluoride concentration: 3 mg/L) the maximum removal efficiency was 97.26%. Results showed that the adsorption equilibrium and kinetic data were matched with the isotherm Langmuir Model (R2 = 0.98) with qmax = 27.31 mg/g and pseudo-second-order reaction (R2 = 0.99). Also, a thermodynamic study exhibited that the adsorption process of fluoride into bivalve shells was an exothermic reaction and could not be a spontaneous adsorption process. Based on the results, the bivalve shell was found as an appropriate adsorbent to remove fluoride from aqueous solutions.

4-Chlorophenol adsorption from water solutions by activated carbon functionalized with amine groups: response surface method and artificial neural networks

“…The effect of influencing variables pH, retention time (min), adsorbent dose (g/L), and initial concentration (mg/L) as input variables on the efficiency of powdered activated carbon functionalized with amine groups in removing of 4-Chlorophenol were investigated as a response variable. The RSM package and CCD approach method determined the optimal condition using R software version 3.3.2.0 (2016-10-31) 25 . The predictor variables were standardized, and then the hierarchical RSM model with all first-order terms, all pure quadratic terms, and all two-way interactions were fitted.…”

Removal of Fluoride From Drinking Water Through Low-Cost Techniques

“…All the selected adsorbents were used individually for experiments in the container system. Water samples were collected every 3, 6, and 9 h [16,17].…”

“…Thermodynamic investigations provided evidence of the exothermic nature of the adsorption process, which cannot be spontaneous. The adsorption kinetics followed a pseudo-secondorder model [17]. In a study, adsorption efficiency was directly related to a temperature beyond 35 °C.…”