KOH-modified bamboo charcoal loaded with α-FeOOH for efficient adsorption of copper and fluoride ions from aqueous solution

Abstract

In this work, bamboo charcoal (BC) is prepared by pyrolysis of bamboo. Then, KOH modification and surface deposition of Goethite (α-FeOOH) are performed to obtain a new KOH-modified BC loaded with α-FeOOH (FKBC) adsorbent for copper (Cu²⁺) and fluoride (F⁻) ion adsorption from aqueous solution. Surface morphology and physiochemical properties of the prepared adsorbent are characterized by scanning electron microscopy-energy dispersive spectrometer, X-ray diffraction, and N₂ adsorption–desorption. The effect of pH, contact time, adsorbent dosage, and initial concentration on Cu²⁺ and F⁻ adsorption is also investigated. In addition, adsorption kinetics and isotherms are fitted to pseudo-second-order kinetics and Langmuir model, respectively. Thermodynamic parameters suggest that the adsorption process is spontaneous and endothermic. The adsorption mechanism is further characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The Cu²⁺ absorption mainly occurs through ion exchange, coordination reactions, and surface precipitation, while the F⁻ adsorption mainly occurs via ion exchange and hydrogen bonding. The selective adsorption experiments reveal that FKBC has good selectivity for Cu²⁺ and F⁻. The adsorption–desorption experimental results indicate that FKBC can be reused for Cu²⁺ and F⁻ adsorption after regeneration. Results indicate that FKBC can be a promising adsorbent for Cu²⁺ and F⁻ removal from aqueous solutions.