Synthesis and Characterization of Carbon-Based Nano-Adsorbent for Dyes Removal from Wastewater

Water pollution is the main part of environmental pollution and it has been increased due to factors such as urbanization and rapid industrialization, considering to human activities in various industrial fields <i>e.g.</i> textile industry, metallurgical, and others. In particular, dyes are hazardous and toxic components, present in trace amounts in wastewater effluents, for its treatment the adsorption method has been the most promising and widely used treatment technique due to its efficient and its flexible operation compared to other methods. Currently, in the nanotechnology field, there are substantial studies researching the potential application of nano- adsorbents for dye removal such as carbon nanotubes (CNTs) and activated carbon (AC) due their physical-chemical properties <i>e.g</i>., large surface area associated with the availability of active binding sites, chemical and thermal properties. These materials can be modified chemically with metallic nanoparticles to increase the surface area and their adsorption capacities through high selectivity and active centers generation. In the present work, multiwalled carbon nanotubes (MWCNTs) and activated carbon from orange peel (AC) were modified to obtain adsorbent materials. Firstly, a functionalization using a mixing acid (HNO₃ and H₂SO₄) was proposed, to improve groups such as oxygen, nitrogen and sulfur on carbon surface materials. Furthermore, MWCNTs and AC surface were modified with nanoparticles with oxide zinc (ZnO) at different concentration (15 and 30 wt%) by precipitation method. The carbon materials were tests to removal methylene blue (MB) and the optimum adsorption conditions were evaluated. The carbon materials (CM) were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Nitrogen (N₂) adsorption-desorption, zeta potential and UV-VIS technique were used to quantify the concentration of MB. Results revealed that CM developed a large surface area from 200 to 1100 m²g^-1 and chemical groups such as OH, C=O and C-O were conserved; adsorption studies reveal that materials with nanoparticles at 30 wt% can removal until 89.5 % of MB considering conditions such as pH 10, time 24 h, adsorbent dose 20 mg, concentration 80 ppm. The overall all results indicated that CM are promising candidates for dye removals.<br/><b>Keywords:</b> carbon nanotubes, activated carbon, nanoparticles, dyes, adsorption.