Effect of hybridization on the value-added activated carbon materials

Activated Carbon and Clay Pellets Coated with Hydroxyapatite for Heavy Metal Removal: Characterization, Adsorption, and Regeneration

In the present work, activated-carbon-containing pellets were preparedby direct chemical activation of sawdust, using clays as a binder. The obtained pellets (ACC) were coated with hydroxyapatite (HAp) nanoparticles (ACC-HAp) to improve adsorption towards Pb(II), Cu(II), Zn(II), and Ni(II). The pellets were characterized by scanning electron microscopy (SEM), by Fourier transform infrared spectroscopy (FTIR), and with a gas sorptometer. The effect of pH, contact time, and initial concentration on adsorption performance was investigated. Additionally, desorption studies were performed, and the regeneration influence on compressive strength and repeated Pb(II) adsorption was investigated. The results showed that, after coating ACC pellets with HAp nanoparticles, the adsorption capacity increased for all applied heavy metal ions. Pb(II) was adsorbed the most, and the best results were achieved at pH 6. The adsorption process followed the pseudo-second-order kinetic model. The adsorption isotherm of Pb(II) is better fitted to the Langmuir model, showing the maximum adsorption capacity of 56 and 47 mg/g by ACC-HAp and ACC pellets, respectively. The desorption efficiency of Pb(II)-loaded ACC-HAp pellets increased by lowering the pH of the acid, resulting in the dissolution of the HAp coating. The best desorption results were achieved with HCl at pH 1 and 1.5. Therefore, the regeneration procedure consisted of desorption, rinsing with distilled water, and re-coating with HAp nanoparticles. After the regeneration process, the Pb(II) adsorption was not affected. However, the desorption stage within the regeneration process decreased the compressive strength of the pellets.

Fabrication of Activated Carbon Fibers with Sheath-Core, Hollow, or Porous Structures via Conjugated Melt Spinning of Polyethylene Precursor

Using polyethylene as carbon precursor, we have fabricated cost-effective carbon fibers with a sheath-core structure via conjugate melt spinning. Low-density polyethylene (LDPE) and high-density polyethylene (HDPE) were used as the sheath and core of the fiber, respectively, while sulfonation with sulfuric acid was conducted to enable the crosslinking of polyethylene. We demonstrated that carbonization and activation of the sheath-core-structured polyethylene fiber can result in a well-developed microporous structure in the sheath layer, and due to the core-sheath structure, the resulting activated carbon fibers exhibit a high tensile strength of ~455 MPa, initial modulus of ~14.4 GPa, and Brunauer-Emmett-Teller (BET) surface area of ~1224 m²/g. Finally, activated carbon fibers with a hollow, sheath-core, and porous were successfully fabricated by controlling the degree of crosslinking of the LDPE/HDPE sheath-core fiber.

Preparation of affordable and multifunctional clay-based ceramic filter matrix for treatment of drinking water

Affordable clay-based ceramic filters with multifunctional properties were prepared using low-cost and active ingredients. The characterization results clearly revealed well crystallinity, structural elucidation, extensive porosity, higher surface area, higher stability, and durability which apparently enhance the treatment efficiency. The filtration rates of ceramic filter were evaluated under gravity and the results obtained were compared with a typical gravity slow sand filter (GSSF). All ceramic filters showed significant filtration rates of about 50-180 m/h, which is comparatively higher than the typical GSSF. Further, purification efficiency of clay-based ceramic filters was evaluated by considering important drinking water parameters and contaminants. A significant removal potential was achieved by the clay-based ceramic filter with 25% and 30% activated carbon along with active agents. Desired drinking water quality parameters were achieved by potential removal of nitrite (98.5%), nitrate (80.5%), total dissolved solids (62%), total hardness (55%), total organic pollutants (89%), and pathogenic microorganisms (100%) using ceramic filters within a short duration. The remarkable purification and disinfection efficiencies were attributed to the extensive porosity (0.202 cm³ g^-1), surface area (124.61 m² g^-1), stability, and presence of active nanoparticles such as Cu, TiO₂, and Ag within the porous matrix of the ceramic filter.