Synthesis of lanthanum-modified clay soil-based adsorbent for the fluoride removal from an aqueous solution and groundwater through batch and column process: mechanism and kinetics

• Published in: Environmental earth sciences 2022-05, Vol.81 (9), Article 253
• Main Authors: Bhan, Chandra, Singh, Jiwan, Sharma, Yogesh Chandra, Koduru, Janardhan Reddy
• Format: Article
• Language: English
• Subjects: Adsorbents; Adsorption; Analytical methods; Aqueous environments; Aqueous solutions; Biogeosciences; Clay; Clay soils; Earth and Environmental Science; Earth Sciences; Electron microscopy; Environmental Science and Engineering; Fixed beds; Fluorides; Fourier transforms; Geochemistry; Geology; Groundwater; Groundwater treatment; Hydrology/Water Resources; Infrared analysis; Kinetics; Lanthanum; Lanthanum oxides; Microscopy; Muffle furnaces; Original Article; Photoelectron spectroscopy; Photoelectrons; Regeneration (biological); Removal; Scanning electron microscopy; Sodium bicarbonate; Sodium hydroxide; Soil; Soils; Spectroscopy; Terrestrial Pollution; Transmission electron microscopy; Uptake; X rays; X-ray diffraction; Zeta potential
• ISSN: 1866-6280; 1866-6299
• DOI: 10.1007/s12665-022-10377-x

In the present work, pond clay was modified with lanthanum and applied for fluoride uptake from an aqueous environment. The clay soil was treated with a 0.1 M solution of lanthanum oxide and heated at 500 ℃ for 90 min in a muffle furnace. The modified clay was characterized by the following techniques: particle size analysis, zeta potential, Fourier-transform infrared, scanning electron microscopy, transmission electron microscopy, pH at the zero point of charge, X-ray diffraction, Brunauer–Emmett–Teller, and X-ray photoelectron spectroscopy. The adsorption experiments revealed that modified clay soil was very effective in removing fluoride with an adsorption capacity of 1.96 mg/g. The fluoride removal was followed well with Langmuir isotherm ( R 2 = 0.999), pseudo-second-order kinetics ( R 2 = 1), and the adsorption was an exothermic process. The performance of lanthanum-modified clay (LMC) in a fixed bed column was evaluated using different models, including the Thomas, Adams–Bohart, Yoon–Nelson, and Clark models. A regeneration study was compared with NaOH and NaHCO 3 and successfully performed for four adsorption cycles. A probable mechanism is proposed including ligand exchange, electrostatic attraction, and inner complexation for fluoride adsorption on the LMC. The developed adsorbent was also tested for the treatment of natural groundwater.