Ultrasound assisted synthesis of Mg-Mn-Zr impregnated activated carbon for effective fluoride adsorption from water

Abstract

High fluoride content in the natural water sources is a serious matter of concern and adsorption is recommended as one of the most convenient, affordable and widely applied defluorination technologies. In this study, a novel composite was synthesized by impregnating magnesium (Mg), manganese (Mn) and zirconium (Zr) on powdered activated carbon (AC) for effective fluoride adsorption and the synthesis was made using sonochemical method. The characterization of the prepared adsorbent AC-Mg-Mn-Zr along with individual metal composites AC-Zr, AC-Mg and AC-Mn were done by SEM, EDX, FTIR, XRD and BET analysis to understand the major functional bonds, and changes in surface chemistry after adsorption. The mechanism of the process was discussed through major reactions involved for individual metals. Due to high point of zero charge (pH = 11.9), the adsorbent was able to remove more than 96% of fluoride consistently with only 1 g/L of optimum adsorbent dosage for a wide pH range (2 to 10). The maximum adsorption capacity obtained was 26.27 mg/g within an equilibrium time of 3 h. More than 96% energy saving was achieved in the sonochemical synthesis route compared to conventional precipitation method of synthesis.

The adsorption of fluoride from aqueous solutions by Fe, Mn, and Fe/Mn modified natural clinoptilolite and optimization using response surface methodology

“…In the pH range 8-11, the surface of the adsorbent materials used is still positively charged and a favorable fluoride adsorption occurs due to the electrostatic force of attraction. Similar results were observed in different fluoride adsorption studies and it was determined that fluoride adsorption decreased considerably at highly acidic and highly basic pH values (Jin et al, 2016;Kagne et al, 2009;Mullick & Neogi, 2019;Sivasamy et al, 2001;Sundaram et al, 2009;Zendehdel et al, 2017;Corral-Capulin et al, 2019).…”

“…The increase in dose from 0.5 to 1.1 g/50 ml for CLP‐FeMn resulted in a sharp increase in fluoride uptake due to the increasing adsorption surface area and vacant pores on the adsorption sites. At doses above 1.1 g/50 ml, the efficiency of fluoride removal slightly increased because of the saturation of fluoride ion on the surface of the adsorbent and decreasing the effective surface area (Mullick & Neogi, 2019; Raghav et al, 2019; Yadav et al, 2006). Considering all these findings, the optimum dose for CLP‐Fe and CLP‐Mn was determined as 1.1 g/50 ml and 1.5 g/50 ml for CLP‐FeMn.…”

“…The effect of initial fluoride concentration on fluoride uptake was investigated in the range of 2.0–50.0 mg/L at room temperature and the results are given in Figure 5. It is noticed that the increment in the initial fluoride concentration induced a decrease in the defluoridation efficiency due to the inadequate surface adsorption sites for CLP‐Fe and CLP‐FeMn (Ghosh & Mondal, 2019; Mullick & Neogi, 2019; Sun et al, 2011). For both adsorbents, the increase in fluoride removal efficiency at high initial fluoride concentration (50 mg/L) was achieved by increasing the amount of adsorbent.…”

Precipitation Methods Using Calcium-Containing Ores for Fluoride Removal in Wastewater

“…F-containing wastewater can be treated by chemical precipitation method [20,21], coagulation and precipitation method [22,23], adsorption method [24][25][26][27][28][29], electrocoagulation method [20,[30][31][32][33], reverse osmosis method [34][35][36], and ion exchange method [37,38]. Generally, chemicals such as CaCl 2 and CaO are added for precipitating fluoride in wastewater.…”

Fluoride Removal from Groundwater by Technological Process Optimization

“…The main objective of defluoridation is to remove the excess of fluoride from aqueous solutions, and to bring it down to acceptable standards [19][20][21]. Sorption techniques and membrane separation processes (nanofiltration, reverse osmosis and electro-dialysis) are the most common methods used to deal with this problem; there are other processes also used for water defluoridation such as, coagulation-precipitation and ion exchange.…”