Modification of Tamarix hispida Biochar by Lanthanum Chloride for Enhanced Fluoride Adsorption from Synthetic and Real Wastewater

Abstract

The purpose of this research was the preparation of Tamarix hispida biochar during a pyrolysis process and then improvement its fluoride adsorption capacity by lanthanum chloride. The biochar powder was amended by lanthanum during a precipitation‐oxidation method to make biochar–lanthanum (biochar–La). Adsorbent characteristics of the fresh and fluoride loaded biochar–La were determined by using Fourier‐transform infrared spectroscopy spectrometer, Brunauer–Emmett–Teller, pH of zero point charge, energy‐dispersive X‐ray spectroscopy, and scanning electron microscopy methods. The mesoporous adsorbent had a surface area of 164.5 m2/g. Effects of some important factors such as initial fluoride concentration (20, 40, and 70 mg/L), biochar–La dose (1–10 g/L), contact time (3–100 min), solution temperature (25–50°C), and initial pH (2–10) were tested. The results showed that fluoride uptake by modified biochar is much more effective than simple one. The adsorption data well followed the Langmuir isotherm (maximum adsorption capacity = 164.23 mg/g) and second‐order kinetic model. Increasing the amount of biochar–La and fluoride concentration was led to increasing and reducing the adsorption efficiency, respectively. The biochar–La adsorbent had a good performance at sixth cycle of reuse (>50% removal). The fluoride content in a real wastewater was reduced from 23 mg/L to around 3 mg/L at conditions of biochar–La: 5 g/L, time: 50 min, and original pH: 6.8. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S298–S305, 2019