Adsorption behavior of carboxymethyl konjac glucomannan microspheres for fluoride from aqueous solution

Abstract

A novel microsphere adsorbent of carboxymethyl konjac glucomannan immobilized with La³⁺ and Al³⁺ (CMKGM–La–Al) was prepared through the sol–gel method and used to adsorb F⁻ from an aqueous solution. Batch experiments were performed on factors such as solution pH, adsorption temperature, initial fluoride concentration and contact time to evaluate the adsorption capacity of the adsorbent. The adsorption process of fluoride could be well described by the linear Langmuir model. The maximum adsorption capacity (q_max) of CMKGM–La–Al for F⁻ was 20.37 mg g⁻¹ at a pH of 2.0, concentration of 40 mg L⁻¹, and 298.15 K. The adsorption kinetic data fitted well with the linear pseudo-second-order model. The thermodynamic parameters of ΔH, ΔS and ΔG showed that the adsorption of F⁻ on CMKGM–La–Al was a spontaneous and endothermic process. A comparison between CMKGM–La–Al and other adsorbents suggested that CMKGM–La–Al could be considered as a promising adsorbent for fluoride removal.