Synthesis of carboxylic graphene oxide‐carboxymethyl chitosan composite and its applications toward the remediation of U⁶⁺, Pb²⁺, Cr⁶⁺, and Cd²⁺ ions from aqueous solutions

Abstract

The current research work deals with the synthesis of a novel composite material of carboxylic graphene oxide-carboxymethyl chitosan (COOH-GO-CMC) composite by ultrasound and microwave-assisted processes. The composite was characterized by Fourier Transform Infra-red spectroscopy, X-ray Powder Diffraction, Raman Spectroscopy, Scanning Electron Microscopy, and X-ray Photoelectron Spectroscopy. The synthesized composite was used to remove heavy toxic metal ions (HTMIs) such as uranium (U 6+ ), lead (Pb 2+ ), chromium (Cr 6+ ), and cadmium (Cd 2+ ) ions from aqueous solutions. The HTMIs removal study was carried out to verify the effects of pH, contact time, amount of adsorbent dose, initial concentration, and temperature. The linear and nonlinear Langmuir and Freundlich adsorption isotherms were fitted to the data of removal studies, and it was observed that the linear Langmuir adsorption isotherm (R 2 > 0.99) was the best-fitted model. The maximum adsorption capacities of COOH-GO-CMC were found to be 74. 62, 416.66, 76.92, and 53.47 mg g À1 for U 6+ , Pb 2+ , Cr 6+ , and Cd 2+ ions, respectively. The kinetics studies, including four types of models (linear and nonlinear pseudo-firstorder, linear and nonlinear pseudo-second-order, Intraparticle diffusion, and Elovich kinetic models), were tested, and the results showed that the linear pseudo-second-order kinetics model (R 2 > 0.99) was the best-fitted model. The thermodynamic studies reveal that the adsorption of HTMIs is a spontaneous (ΔG < 0) and exothermic (ΔH < 0 and ΔS > 0) process in nature.adsorption isotherm, carboxymethyl chitosan, graphene oxide, heavy metal ion removal | INTRODUCTIONAny metallic element with a comparatively high density that is toxic or poisonous even at low concentrations is referred to as "heavy metal." Heavy metals are defined as metals with an atomic number greater than 20 and an atomic density greater than 4 g cm À3 , or 5 times the density of water. [1] As a result of rapid industrialization, hazardous contaminants are discharged in large quantities into different water bodies. As these contaminants are non-degradable, toxic, cancer-causing agents, and difficult to remove from water, heavy toxic metal ions

Removal of Cu(II) from aqueous solutions by zinc oxide‐montmorillonite composite

“…As the adsorbent dosing increases, the adsorption sites provided by the adsorbent become more and more abundant, resulting in a lower equilibrium adsorption concentration of Cu(II), which contributes to the low adsorption capacity and high removal rate. This result is comparable to the findings on the removal of U(VI), Pb(II), Cr(VI), and Cd(II) from water by carboxylic graphene oxidecarboxymethyl chitosan composite prepared by Patel et al [37]. Hence, considering the efficiency and economy, an adsorbent dosage of 0.025 g is chosen as the experimental dosage for the following sections.…”