Volcanic rock‐based ceramsite adsorbent for highly selective fluoride removal: function optimization and mechanism

Abstract

BACKGROUND: While various granular adsorbents have been studied for fluoride removal from water, this study focuses on the optimization of mixture proportions of volcanic rock, bentonite, corn starch and aluminum sulfate using a four-component simplex-centroid mixture design (SCMD) method to achieve preferable fluoride removal ratio and ceramsite mechanical strength. To illustrate the adsorption mechanism, a series of experiments, including adsorption isotherms, adsorption kinetics and effects of pH value and co-existing anions, was carried out. RESULTS: The synthesized adsorbent was mesoporous with 77.82% pore size distribution in the range 1.70-38.80 nm by detailed physicochemical characterization. A stable fluoride removal ratio (87.5%) was obtained in the wide pH range of 4.0-11.0, and the adsorption capacity was 10.17 mg g −1 at 298 K. The adsorbent remained high selectivity for F − in the presence of sulfate (SO 4 2− ), chloride (Cl − ) and nitrate (NO 3 − ), while carbonate (HCO 3 − ) posed a slight adverse effect on F − adsorption due to ion competition. This adsorption process was well fitted with the pseudo-second-order kinetic model and the Freundlich isotherm model. Electrostatic attraction and M + -H 2 O and M + -F ligand exchange were dominant in the adsorption mechanisms. CONCLUSION: The synthesized ceramsite adsorbent will be competitive in the application for F − removal from aquatic environments.

Volcanic rock powder residues as precursors for the synthesis of adsorbents and potential application in the removal of dyes and metals from water

“…Due to the chemical composition of the waste rock powder, studies have sought to verify their potential as an adsorbent, being this applied directly or functionalized with another element (Zhu et al 2015;Asere et al 2017;Tejeda et al 2017;Bugarčić et al 2018;Chao et al 2019). Recently, alkaline activated materials, such as geopolymers, have been gaining space in adsorption studies, and very promising results have been achieved in treating effluents containing dyes (Vieira et al 2021).…”

“…Recently, alkaline activated materials, such as geopolymers, have been gaining space in adsorption studies, and very promising results have been achieved in treating effluents containing dyes (Vieira et al 2021). Chao et al (2019) synthesized a volcanic rock-based ceramsite adsorbent for selective fluoride removal. The fluoride adsorption capacity was 10.16 mg g −1 at 298 K. Bugarčić et al (2018) sought to determine the potential of raw volcanic rock as an adsorbent of heavy metals in anionic form (chromates, Cr; arsenates, As; and selenates, Se).…”

Microbial Communities on Different Packing Media in Biofilter

“…Comparatively, volcanic rock has the better treatment effect, while ceramiste is easier to obtain. Many scholars have explored the treatment effect of the two materials, but failing to compare the microorganism communities between them [4][5][6][7].…”