Synthesis of a novel functional group-bridged magnetized bentonite adsorbent: Characterization, kinetics, isotherm, thermodynamics and regeneration

Advances in Amine-Surface Functionalization of Inorganic Adsorbents for Water Treatment and Antimicrobial Activities: A Review

In the last decade, adsorption has exhibited promising and effective outcomes as a treatment technique for wastewater contaminated with many types of pollutants such as heavy metals, dyes, pharmaceuticals, and bacteria. To achieve such effectiveness, a number of potential adsorbents have been synthesized and applied for water remediation and antimicrobial activities. Among these inorganic adsorbents (INAD), activated carbon, silica, metal oxide, metal nanoparticles, metal-organic fibers, and graphene oxide have been evaluated. In recent years, significant efforts have been made in the development of highly efficient adsorbent materials for gas and liquid phases. For gas capture and water decontamination, the most popular and known functionalization strategy is the chemical grafting of amine, due to its low cost, ecofriendliness, and effectiveness. In this context, various amines such as 3-aminopropyltriethoxysilane (APTES), diethanolamine (DEA), dendrimer-based polyamidoamine (PAMAM), branched polyethyleneimine (PEI), and others are employed for the surface modification of INADs to constitute a large panel of resource and low-cost materials usable as an alternative to conventional treatments aimed at removing organic and inorganic pollutants and pathogenic bacteria. Amine-grafted INAD has long been considered as a promising approach for the adsorption of both inorganic and organic pollutants. The goal of this review is to provide an overview of surface modifications through amine grafting and their adsorption behavior under diverse conditions. Amine grafting strategies are investigated in terms of the effects of the solvent, temperature, and the concentration precursor. The literature survey presented in this work provides evidence of the significant potential of amine-grafted INAD to remove not only various contaminants separately from polluted water, but also to remove pollutant mixtures and bacteria.

Synthesis of amino-functionalized bentonite/CoFe2O4@MnO2 magnetic recoverable nanoparticles for aqueous Cd2+ removal

Magnetic nano-composite materials have been attracting considerable attention due to their unique properties and versatile applications. In this study, a novel magnetic amino-functionalized conjugate adsorbent, named as bentonite/CoFe₂O₄@MnO₂-NH₂ (BCFMNs), was synthesized by combining APTES and MnO₂ with magnetic bentonite. XRD, FT-IR, SEM, EDS, TEM, and VSM techniques were used to characterize its structure and magnetic properties. Results were in indicative of productive synthesis, well-defined architecture and satisfactory magnetism. BET examinations illustrated 84.97m²/g of specific surface area, 0.15cm³/g of pore volume and 7.02nm average pore size. The effect parameters such as adsorbent dosage, contact time, initial concentration and ion selectivity and recycling were evaluated and optimized systematically. Also, the metal concentrations were measured by ICP-MS spectrometer. The feasibility of the BCFMNs for removal of Cd²⁺ from aqueous solution was also evaluated by adsorption experiments with the maximal adsorption efficiency for Cd²⁺ up to 98.88%. Cd²⁺ adsorption could be interpreted by the Langmuir adsorption isotherm and the maximum adsorption capacity was 115.79mg/g. The results revealed that the adsorbent still had higher selectivity of Cd²⁺ removal even in the presence of high concentration coexisting cations. The as-prepared magnetic conjugate adsorbent could be recycled by taking advantage of its magnetic properties. The distinctive structure of BCFMNs and its excellent adsorption performance of cadmium reflects its prospective application in water treatment.

Synthesis of Porous Fe/C Bio-Char Adsorbent for Rhodamine B from Waste Wood: Characterization, Kinetics and Thermodynamics

In the past decades, dyes waste waters produced from industries have become a major source of environmental pollution causing the destruction of aquatic communities in the ecosystem and greatly threatened human health. Herein, a novel magnetic adsorbent was synthesized by carbonizing iron (III) 2,4-pentanedionate (Fe(acac)3) pre-enriched forestry waste wood at a pyrolysis temperature of 1000 °C. The characterization of the adsorbent conducted via SEM, EDS, VSM, XRD, XPS, and FT-IR spectroscopy. The adsorption trend followed the pseudo-second order kinetics model. The corresponding adsorption performance was efficient with an equilibrium time of only 1 min. Affect factors on the adsorption performance, such as adsorbent dosage, contact time and temperature, were investigated. The magnetic bio-char showed a high adsorption capacity and an efficient adsorption toward RhB, implying great potential application in the treatment of colored wastewaters.

Design and testing of a pilot scale magnetic separator for the treatment of textile dyeing wastewater

Iron nanoparticles can be incorporated on the structure of natural clays to obtain magnetic clays, an adsorbent that be easily removed from a wastewater by magnetic means. Magnetic clays have high adsorption capacities of different contaminants such as heavy metals, fungicides, aromatic compounds and colorants and show rapid adsorption kinetics, but crucial data for achieving its full or pilot scale application is still lacking. In this work, magnetic bentonites with different amounts of magnetite (iron fractions on the clay of 0.55, 0.6 and 0.6) were used to remove color from a real textile wastewater. On a first stage the optimal conditions for the adsorption of the dye, including pH, temperature and clay dosage were determined. Also design parameters for the separation process such as residence time, distance from magnet to magnetic clay and magnet strength were obtained. Finally a pilot scale magnetic drum separator was constructed and tested. A removal of 60% of the dye from a wastewater that contained more than 250 ppm of azo dye was achieved with only 10 min of residence time inside the separator.

Synthesis of Magnetic Wood Fiber Board and Corresponding Multi-Layer Magnetic Composite Board, with Electromagnetic Wave Absorbing Properties

With the rapid growth in the use of wireless electronic devices, society urgently needs electromagnetic wave (EMW) absorbing material with light weight, thin thickness, wide effective absorbing band width, and strong absorption capacity. Herein, the multi-layer magnetic composite boards are fabricated by hot-pressing magnetic fiber boards and normal veneer layer-by-layer. The magnetic fibers obtained using in-situ chemical co-precipitation are used to fabricate magnetic fiber board by hot-pressing. The magnetic wave absorbing capacities of the magnetic fiber boards obtained with 72 h impregnation time exhibit strongest adsorption capacities of −51.01 dB with a thickness of 3.00 mm. It is proved that this outstanding EMW absorption property is due to the strongest dielectric loss, the optimal magnetic loss, and the dipole relaxation polarization. Meanwhile, the EMW absorbing capacities of the corresponding multi-layer composite magnetic board increases from −14.14 dB (3-layer) to −60.16 dB (7-layer). This is due to the generated multi-interfaces between magnetic fiber board and natural wood veneer in the EMW propagation direction, which significantly benefit multireflection and attenuation of the incident waves. The results obtained in this work indicate that natural wood fibers are of great potential in the fabrication of magnetic multi-layer boards treated as EMW absorbers via a low cost, green, and scalable method.