Adsorption performance and physicochemical mechanism of MnO2-polyethylenimine-tannic acid composites for the removal of Cu(II) and Cr(VI) from aqueous solution

Fabrication of a poly(m‑aminophenol)/3-aminopropyl triethoxysilane/graphene oxide ternary nanocomposite for removal of Cu(II) from aqueous solution

Three composites based on Poly (meta-aminophenol) (PmAP), (3-aminopropyl) triethoxysilane (APTES) and graphene oxide (GO) were synthesized with initial GO dispersion of 3.3, 6.6, and 9.9 mg/mL. First, in-situ polymerization of meta-aminophenol monomer on the surface of graphene oxide (GO) was carried out. Then, the hydroxyl groups of both the GO and the polymer were targeted using (3-aminopropyl) triethoxysilane (APTES) to stop the polymer solubility, increase adsorption sites, and bind the two components. The obtained three composites were applied for efficient removal of Cu(II) from polluted water. PmAP/APTES/GO(6.6) composite was the best one for the uptake of Cu(II) with a maximum adsorption capacity of 324.54 mg/g at 40 °C and pH 7 according to Langmuir. PmAP/APTES/GO(6.6) hybrid composite was characterized by different techniques. The adsorption of Cu(II) on this composite was optimized under various experimental conditions. Furthermore, the isotherm data of the uptake of Cu(II) on PmAP/APTES/GO(6.6) were found to agree with the Freundlich and Langmuir model's linear and nonlinear forms. Chemosorption was suggested by the Dubinin-Radushkevich (D-R) isotherm model as the calculated mean sorption energy exceeds 16 kJ/mol. The thermodynamic analysis of the adsorption process reflects an endothermic, spontaneous process that leads to more disorder at the solid-liquid interface. The chemical interactions between Cu(II) versus oxygen and nitrogen of the functional groups on the surface were demonstrated by X-ray Electron Spectroscopy (XPS). Five cycles of adsorption and desorption of Cu(II) from the prepared composite were carried out with a loss of only 6.3% of its adsorption capacity.

Plasma-assisted MnO surface engineered activated carbon felt for enhanced heavy metal adsorption

This study explores the enhanced adsorption performance of activated carbon felt (ACF) for Cu(II) and Cd(II) ions, achieved using a dual-synergistic approach combining MnO coating and plasma treatment. ACF's intrinsic properties, including a high surface area (~ 1000-2000 m²/g), large porosity, and excellent mechanical stability, make it a promising material for environmental applications. However, its limited surface functional groups hinder its adsorption efficiency for heavy metals. Conventional acid treatments, though effective in introducing functional groups, compromise ACF's structural integrity and pose environmental hazards. The non-thermal plasma method addresses these challenges by introducing oxygen-rich functional groups and MnO species without using harmful chemicals, preserving the material's mechanical and morphological properties. This study addresses key challenges in adsorption technologies, such as inefficiencies in multi-contaminant systems and adsorbent degradation through plasma-aided modifications. The synergistic modification enhances adsorption performance by leveraging mechanisms such as ion exchange, complexation, and co-precipitation. Adsorption experiments revealed maximum adsorption capacities of 163.39 mg/g for Cu(II) and 214.59 mg/g for Cd(II), with an extended equilibrium time of 720 min at pH 5. This research highlights the significance of plasma-aided modification strategies for developing sustainable and efficient heavy metal adsorbents, contributing to advancements in wastewater treatment technologies.

The Removal of Pb2+ from Aqueous Solution by Using Navel Orange Peel Biochar Supported Graphene Oxide: Characteristics, Response Surface Methodology, and Mechanism

The value-added utilization of waste resources to synthesize functional materials is important to achieve the environmentally sustainable development. In this paper, the biochar supported graphene oxide (BGO) materials were prepared by using navel orange peel and natural graphite. The optimal adsorption parameters were analyzed by response surface methodology under the conditions of solution pH, adsorbent dosage, and rotating speed. The adsorption isotherm and kinetic model fitting experiments were carried out according to the optimal adsorption parameters, and the mechanism of BGO adsorption of Pb2+ was explained using Scanning Electron Microscope (SEM-EDS), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). Compared with virgin biochar, the adsorption capacity of Pb2+ on biochar supported graphene oxide was significantly increased. The results of response surface methodology optimization design showed that the order of influence on adsorption of Pb2+ was solution pH > adsorbent dosage > rotating speed. The optimal conditions were as follows: solution pH was 4.97, rotating speed was 172.97 rpm, and adsorbent dosage was 0.086 g. In the adsorption−desorption experiment, the desorption efficiency ranged from 54.3 to 63.3%. The process of Pb2+ adsorption by BGO is spontaneous and endothermic, mainly through electrostatic interaction and surface complexation. It is a heterogeneous adsorption process with heterogeneous surface, including surface adsorption, external liquid film diffusion, and intra-particle diffusion.