Phenol Removal from Aquatic Solution Using Three Carbon Nanostructured Adsorbents: Investigation of the Effective Parameters and Adsorption Kinetic

Phenol and its derivatives are considered as one of the major environmental pollutants especially in aquatic ecosystems due to its toxicity, carcinogenic effect, and low biological degradation. The aim of the present work is to compare three carbon nanoadsorbent in phenol removal from water and to investigate adsorption kinetics. In this regard, Graphene, CMK-3, and multi-wall carbon nanotube (MWCNT) were selected while several techniques such as X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Barrett-Joyner-Halenda (BJH) and scanning electron microscope (SEM) were used to characterize the adsorbents. In the next step, the effective factors on the adsorption process, i.e. adsorbent dose, pH, and contact time were studied. Moreover, the kinetics of the phenol sorption process were tested using the Pseudo-first-order, Pseudo-second-order, and Elovich models. The results have shown that increasing the amount of adsorbent loading leads to increase the adsorption efficiency and decrease in adsorption capacity, both variations indicating nonlinear behavior. Furthermore, the highest removal for graphene, MWCNT and CMK-3 was observed at pH 8. It has also been found that the optimum time to saturate adsorption active sites is about 40 minutes, and more contact time does not change the process efficiency. In addition, kinetic study has indicated that for all adsorbents, pseudo second order model has fitted better the experimental data than Pseudo first order and Elovich models. The adsorption mechanism was discussed based on experimental results. The results have indicated that for all adsorbents, the π-π interactions is an important parameter whereas in the case of MWCNT, strong force between phenol and copper impurities; moreover, in the case of CMK-3, strong hydrogen bond between phenol and hydroxyl/carboxyl groups are important parameters in in the adsorption process. Finally, among the adsorbents, CMK-3 has been selected as the optimum adsorbent for phenol removal due to its higher yield and efficiency.