||Several water treatment plants in Southern Taiwan have enhancedtheir traditional treatment processes. Adsorption is an ideal and effective water treatment method because trace amounts of perchlorate have been detectedin the raw water of Southern Taiwan in recent years.|
This study adopted carbon nanotubes (CNTs) and magnetic ion-exchange (MIEX) resins to adsorb the perchlorate in water for investigating the efficiency of perchlorate removal and the effects of relevant factors. CNTs and MIEX resins are among the multiple types of novel adsorbent available in the market. By using the two adsorbents for conducting equilibrium adsorption tests and model assessment, this study ascertained the adsorption characteristics and behavior of perchlorate.
The results indicated that the adsorption behavior of CNTs and MIEX resins on perchlorate was mainly influenced by pH value, ionic strength, and temperature. The adsorption capacity in the dynamic and equilibrium adsorption experiments was analyzed usingadsorption models. The CNTs and MIEX resins achieved equilibrium in approximately 8h, and the adsorption capacity increased astheperchlorate concentration increased and ionic strength decreased. The models of modified Freundlich equation, pseudo-first-order equation, and pseudo-second-order equation were adopted for determining the optimal adsorption model. The results revealed that the modified Freundlich equation was optimal for the perchlorate adsorption by CNTs, whereas the pseudo-first-order equation was optimal for the perchlorate adsorption by MIEX resins.
According to the results of the equilibrium adsorption tests,perchlorate at low pH was favorable for the performance of the two adsorbents. The isothermal adsorption results of perchlorate, in which adsorptioncapability and affinity increased as thetemperaturedecreased, were applicable to both the Langmuir and the Freundlich models. In a thermostatic environment of 5–45 °C, the results of isothermal equilibrium adsorption tests indicated that the maximumadsorption capacity of the CNTs,MIEX resins,and the control, granular activated carbon,was 10.03–13.64mg/g, 70.15–82.01 mg/g, and28.21–33.87 mg/g, respectively. Therefore, low pH values, low ionic strength, and low temperature are favorable for CNTs and MIEX resins inremoving perchlorate.