Electrocoagulated Metal Hydroxide Sludge for Fluoride and Arsenic Removal in Aqueous Solution: Characterization, Kinetic, and Equilibrium Studies

The present study aimed to minimize the environmental impact from the disposal of electrocoagulated metal hydroxide sludge (EMHS) generated during an electrocoagulation process using aluminum electrode by reusing it as an effective adsorbent for simultaneous removal of fluoride ion (F − ) and arsenic (As) from aqueous solutions. The adsorbent was characterized by using coupled plasma optical emission spectroscopy (ICP-OES), surface areas and porosity properties, point of zero charge, and X-Ray diffractometry techniques. The surface morphology of adsorbent was studied by scanning electron microscopy (SEM). The dissolution of the adsorbent in function of pH was analyzed in batch experiments. Batch adsorption tests were employed to evaluate the removal and adsorption capacity of adsorbent, under conditions of contact time and adsorbate concentration. In order to determine maximum adsorption capacity of adsorbent and to understand the nature of reaction on their surface, the Langmuir and Freundlich isotherm were calculated. Preferable fitting of the Langmuir isotherm over Freundlich isotherm suggests monolayer coverage of adsorbate at the surface of the adsorbent. Data obtained were also applied to pseudo-first-order and pseudo-second-order equations. The rates of adsorption were found to conform to pseudo-second-order kinetics. The findings of this study revealed that the reuse of EMHS is a promising and efficient adsorbent in order to diminish the fluoride and arsenic pollution from drinking water.