Fluoride removal by palm shell waste based powdered activated carbon vs. functionalized carbon with magnesium silicate: Implications for their application in water treatment. (January 2020)

• Record Type: Journal Article
• Authors: Choong, Choe Earn; Wong, Kien Tiek; Jang, Seok Byum; Nah, In Wook; Choi, Jaeyoung; Ibrahim, Shaliza; Yoon, Yeomin; Jang, Min
• Is Part Of: Chemosphere. Volume 239(2020)
• Publication Date: 2020-01
• Subjects: Magnesium silicate -- Adsorption -- Fluoride -- Palm-shell activated carbon; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.124765
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: In this study, palm shell activated carbon powder (PSAC) and magnesium silicate (MgSiO3 ) modified PSAC (MPSAC) were thoroughly investigated for fluoride (F − ) adsorption. F − adsorption isotherms showed that PSAC and MPSAC over-performed some other reported F − adsorbents with adsorption capacities of 116 mg g −1 and 150 mg g −1, respectively. Interestingly, the MgSiO3 impregnated layer changed the adsorption behavior of F − from monolayer to heterogeneous multilayer based on the Langmuir and Freundlich isotherm models verified by chi-square test (X 2 ). Thermodynamic parameters indicated that the F − adsorption on PSAC and MPSAC was spontaneous and exothermic. PSAC and MPSAC were characterized using FESEM-EDX, XRD, FTIR and XPS to investigate the F − adsorption mechanism. Based on the regeneration tests using NaOH (0.01 M), PSAC exhibited poor regeneration (<20%) while MPSAC had steady adsorption efficiencies (∼70%) even after 5 regeneration cycles. This is due to highly polarized C–F bond was found on PSAC while Mg–F bond was distinguished on MPSAC, evidently denoting that the F − adsorption is mainly resulted from the exchange of hydroxyl (-OH) group. It was concluded that PSAC would be a potential adsorbent for in-situ F − groundwater remediation due to its capability to retain F − without leaching out in a wide range pH. MPSAC would be an alternative adsorbent for ex-situ F − water remediation because it can easily regenerate with NaOH solution. With the excellent F − adsorption properties, both PSAC and MPSAC offer as promising adsorbents for F − remediation in the aqueous phase. Highlights: MgSiO3 impregnated on PSAC for fluoride removal was studied for the first time. MPSAC showed higher fluoride adsorption capacities compared to PSAC. Anions inhibited F − adsorption with the following sequence: Cl − < NO3 − < SO4 2- . PSAC had stable sequestration capacities of fluoride due to strong C–F bond formation. MPSAC had high regeneration capacities for ex-situ fluoride treatment using NaOH.