Eco-Friendly Porous Carbon Materials for Wastewater Treatment

Different porous carbon materials were applied to remove organic compounds and heavy metals from wastewater. Hierarchically, porous nitrogen rich monolithic carbon (HPC) was synthesized through the sol-gel synthesis method and carbonization process. Rice husk (RH), an agricultural waste material followed by carbonization at two different temperatures (RH400 and RH600) was used as the naturally generated porous carbon composite. Activated carbon (AC) was used as the control. According to the FT-IR spectra, different functional groups are present in all adsorbents. Scanning electron microscopic (SEM) images show an irregular shaped, random disordered macropore structure in RH and a robust sponge-like disordered macropore structure with ligaments in HPC. Transmission electron microscopic (TEM) images of these materials show a disordered mesopore network. Adsorption capacities of these porous carbon materials were determined for organic dyes and metal ions. Methylene blue and Methyl orange were used as the model organic compounds and Pb²⁺, Cu²⁺, Ni²⁺, and Cd²⁺ ions were selected as the metal ions. The experimental data demonstrate that the adsorption capacity of AC for Methyl orange (5.88 mg/g) is much higher than that of the alternatives (RH400–1.97 mg/g, RH600–0.69 mg/g, and HPC – 1.14 mg/g). Adsorption capacity of all the adsorbents for Methylene blue is quite similar. Adsorption capacity of RH400 for Pb²⁺ is much higher than that of RH600, AC and HPC. RH400 has a greater adsorption for Cu²⁺ and Ni²⁺ than the other adsorbents. All adsorbents show a low adsorption capacity for Cd²⁺. RH400 is a promising adsorbent for wastewater purification.