Abstract
A novel lanthanum/modified fly ash (La/MFA) composite adsorbent prepared by simple solution reaction was used for the adsorption of Congo Red (CR) dye from aqueous solution. The morphology and particle size distribution of the composite were characterized, and the equilibrium adsorption was researched. The results show that the adsorption of CR onto La/MFA can reach equilibrium in 30 minutes. The entire adsorption process can be well described by pseudo-second-order kinetic equation at different temperatures. The value of apparent adsorption activation energy is 16.2kJ/mol. The isothermal data conform to the Langmuir model with the maximum adsorption capacity of 714 mg/g at 298K. According to the negative values of Gibbs free energy change (ΔG°) and enthalpy change (ΔH°), and reduction of Langmuir adsorption coefficient with the increase of temperature, the adsorption system from 298K to 328K is confirmed to be of spontaneous and exothermic nature. The results of SEM and particle size analysis indicate that the particle sizes and specific surface of La/MFA are smaller and coarser than those of FA. As a low-value composite adsorbent, La/MFA is especially effective for the removal of high concentration CR.
Published Version
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