Recyclable Carbon-Based Hybrid Adsorbents Functionalized with Alumina Nanoparticles for Water Remediation

Developing and improving adsorbent materials for wastewater treatment have become crucial for achieving recyclable water and keeping the environment safe. Carbon materials are modified with alumina (Al2O3) using various doping ratios and a solvothermal treatment. The process aims to combine the advantages of stable carbon and alumina materials with an efficient adsorbent for methylene blue removal. Fabricated materials including carbon and carbon/alumina derivatives were characterized with TEM, SEM, EDS, XRD, and FTIR, revealing successful surface modifications. The carbon materials exhibited pore diameters between 23 and 39 µm, while the modified ones showed pore diameters between 1.68 and 6.08 µm. The alumina nanoparticles were formed on a carbon surface with a particle size between 174 nm and 179 nm. Fabricated adsorbents were applied for the removal of methylene blue by adsorption at pH 4. The equilibrium and steady state adsorption stage was achieved after 2 h of reporting fast adsorption behavior. Low ratio carbon doping with alumina improved the adsorption capacity for methylene blue removal, while the excessive doping of carbon materials with alumina led to a reduction in adsorption efficiency. The application of pseudo-first-order and pseudo-second-order kinetic models indicated a fast adsorption mechanism, which agreed with the second-order model. The adsorption capacity for methylene blue was found to be 234 mg/g. Adsorption-isotherms including the Langmuir and Freundlich models were applied to investigate the adsorption mechanism. The results indicate that the Langmuir model fits with the adsorption data, which suggests a monolayer adsorption process.