title: Synthesis and performance evaluation of Al/Fe oxide coated diatomaceous earth in groundwater defluoridation: Towards fluorosis mitigation.
abstract: The quest to reduce fluoride in groundwater to WHO acceptable limit of 1.5 mg/L to prevent diseases such as teeth mottling and skeletal fluorosis was the motivation for this study. Al/Fe oxide-modified diatomaceous earth was prepared and its defluoridation potential evaluated by batch method. The sorbent with pHpzc 6.0 ± 0.2 is very reactive. The maximum 82.3% fluoride removal attained in 50 min using a dosage of 0.3 g/100 mL in 10 mg/L fluoride was almost attained within 5 min contact time; 81.3% being the percent fluoride removal at 5 min contact time. The sorbent has a usage advantage of not requiring solution pH adjustment before it can exhibit its fluoride removal potential. A substantial amount of fluoride (93.1%) was removed from solution when a sorbent dosage of 0.6 g/100 mL was contacted with 10 mg/L fluoride solution for 50 min at a mixing rate of 200 rpm. The optimum adsorption capacity of the adsorbent was 7.633 mg/g using a solution containing initially 100 mg/L fluoride. The equilibrium pH of the suspensions ranged between 6.77 and 8.26 for 10 and 100 mg/L fluoride solutions respectively. Contacting the sorbent at a dosage of 0.6 g/100 mL with field water containing 5.53 mg/L at 200 rpm for 50 min reduced the fluoride content to 0.928 mg/L-a value below the upper limit of WHO guideline of 1.5 mg/L fluoride in drinking water. The sorption data fitted to both Langmuir and Freundlich isotherms but better with the former. The sorption data obeyed only the pseudo-second-order kinetic, which implies that fluoride was chemisorbed.
authors.affiliation: a Department of Ecology and Resource Management , University of Venda , Thohoyandou , South Africa.|b Environmental Remediation and Pollution Chemistry Research Group, School of Environmental Sciences, University of Venda , Thohoyandou , South Africa.
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Izuagie
authors.affiliation: a Department of Ecology and Resource Management , University of Venda , Thohoyandou , South Africa.|b Environmental Remediation and Pollution Chemistry Research Group, School of Environmental Sciences, University of Venda , Thohoyandou , South Africa.
authors.forename: Wilson M
authors.initials: WM
authors.lastname: Gitari
authors.affiliation: c Department of Hydrology and Water Resources , University of Venda , Thohoyandou , South Africa.
authors.forename: Jabulani R
authors.initials: JR
authors.lastname: Gumbo
mesh_terms: D000327:Adsorption; D007692:Diatomaceous Earth / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005459:Fluorides / Q000737:chemistry*; D060587:Groundwater / Q000737:chemistry*; D007700:Kinetics; D010087:Oxides / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D010087:Oxides; D014874:Water Pollutants, Chemical; D007692:Diatomaceous Earth; D005459:Fluorides
keywords: Defluoridation; diatomaceous earth; fluorosis; groundwater; mitigation; synthesis