Adsorbent For Removal Of Contaminants Research Articles

Novel chitosan–clay–iron nanocomposites supported on anodic aluminum as an efficient plate-shaped adsorbent for the removal of arsenic and dye from aqueous solutions

Design and synthesis of plate-shaped adsorbents supported on anodized aluminum as a substrate were successfully carried out for the adsorption of methyl orange (MO) and arsenic [As(V)] ions in aqueous solutions. Chitosan, clay, and iron was also used on the anodized aluminum as a substrate to make a nanocomposite adsorbent. The specific properties of the prepared samples were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Brunauer–Emmett–Teller (BET) analysis to determine the textural structure of the nanocomposites. The FESEM results showed that the formation of pores over the anodic surface was strongly related to anodizing time. Aluminum oxide and iron (hematite) phases were detected by XRD, which showed that the composite adsorbents were well synthesized. Isotherm adsorption was conducted using two models, of which the Langmuir model was in good agreement with the experimental results. The calculated maximum adsorption capacities based on the Langmuir equation for the adsorption of MO and As(V) ions were 53.48 and 14.70 mg/g, respectively. Pseudo first- and second-order models were used to demonstrate the adsorption mechanism of the anionic pollutants over the supported nanocomposites. The kinetic results indicated that the linearized pseudo second-order equation conformed best with the experimental data. The adsorption capacity was measured in six consecutive cycles to demonstrate the performance of the anodic adsorbent for removal of contaminants. The results illustrated 10 % and 15 % reductions in adsorption capacity of the anodized nanocomposite following six repeated cycles for MO and As(V) adsorption, respectively.

Efficient simultaneous removal of tetracycline and cefazolin from aqueous solution using a novel adsorbent based on zero-valent iron nanoparticles supported by montmorillonite and graphene oxide: isotherms, kinetic, and thermodynamic studies

ABSTRACT In recent years, antibiotics in aqueous solutions have drawn extensive attention due to their harmful effect on human health and the environment. In this study, efficient and rapid adsorption of two antibiotics, including tetracycline (TC) and cefazolin (CFZ) on synthesised montmorillonite (Mt)/nano zero-valent iron (nZVI)/graphene oxide (GO) from aqueous solutions was studied. The prepared adsorbent was characterised by scanning electron microscope (SEM), energy dispersive X-Ray (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), and vibrating sample magnetometer (VSM). One-factor-at-a-time (OFAT) method was used to optimise the experimental factors. The maximum removal percentage was achieved at pH of 7, an adsorbent dosage of 0.4 g, contact time of 7 min = TC and 10 min = CFZ, initial concentration of 5 mg L−1, and a temperature of 298 K. The evaluation of isotherm models indicated that the Langmuir isotherm with a coefficient of determination (R2) value of 0.9992 for both antibiotics was selected as the best fitting model to describe the adsorption process. The maximum adsorption capacities (qmax) of Mt-nZVI-GO were obtained at 43.24 mg g−1 for TC and 20.36 mg g−1 for CFZ. Furthermore, the pseudo-second-order (PSO) kinetic model fitted well for TC (R2 = 0.9937) and CFZ (R2 = 0.9997). Thermodynamic parameters, i.e. adsorption Gibbs free energy (ΔG0), standard enthalpy (ΔH0), and standard entropy (ΔS0) were estimated. It was found that the adsorption had spontaneous and exothermic in nature. The results revealed that Mt-nZVI-GO could be used as a simple, efficient, and eco-friendly adsorbent for the simultaneous removal of contaminants in aqueous media.

Preparation and morphological and physicochemical characterization of pillared clays from bentonite

Mineral grade and commercial grade bentonite pillared clays were prepared with SnO2. This is to create adsorbents for removal of contaminants from water. The initial and modified clays were characterized by X-ray fluorescence (XRF), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and nitrogen sortometry. The results of the chemical analysis (XRF) clearly confirm the incorporation of tin in the modified materials. The analysis by SEM and nitrogen sortometry verified the successful modification of the clays by incorporation of tin dioxide species, and the appearance of mesoporous structures with an increase in the values of surface area and porosity.

Influence of lipid extraction and processing conditions on hydrothermal conversion of microalgae feedstocks – Effect on hydrochar composition, secondary char formation and phytotoxicity

This study investigated the effect of lipid extraction of microalgae feedstocks subjected to hydrothermal carbonization (HTC) with regard to the carbonization degree, chemical composition and phytotoxicity of hydrochars produced under different reaction temperatures and residence times. Special attention was given to the formation and composition of secondary char, as this part of the hydrochar may be of particular importance for environmental and technical applications. A microalgae polyculture grown in municipal wastewater was extracted to retrieve lipids, and both unextracted (MA) and extracted microalgae (EMA) were used to produce hydrochars at 180–240 °C for 1–4 h. The composition of the hydrochars was thoroughly characterized by elemental analysis, thermogravimetric analysis and pyrolysis–gas chromatography/mass spectrometry analysis. MA exhibited a greater carbonization degree than EMA and contained higher amounts of secondary char under the same processing conditions. During the carbonization of EMA, more decomposition products remained in the liquid phase and less polymerization occurred than for MA, which explained the lower solid yield of EMA-derived hydrochars in comparison to MA hydrochars. Consequently, although they contained potentially toxic substances (i.e., carboxylic acids, aldehydes and ketones), the EMA-derived hydrochars exhibited a lower phytotoxic potential. This indicates that low-temperature hydrochars containing less than 10% of extractives might be suitable as soil amendments, whereas extractive-rich hydrochars would be more appropriate for other long-term applications, such as adsorbents for contaminant removal, energy storage and composite materials. Detailed characterization of microalgae-derived hydrochars is required to enable the most suitable application areas to be identified for these materials, and thereby make full use of their function as carbon sinks.

A robust approach towards green synthesis of polyaniline-Scenedesmus biocomposite for wastewater treatment applications

The current study presents the synthesis of polyaniline-Scenedesmus biocomposite and its use as an efficient adsorbent for removal of contaminants from aqueous solutions. Initially, the Scenedesmus strain was cultivated in municipal wastewater. The Physico-chemical analysis of municipal wastewater after microalgae growth depicted 85.5% reduction in total nitrogen, 83.2% reduction in phosphorus and 89.3% reduction in chemical oxygen demand which clearly reveals that this strain can be efficiently used to avoid eutrophication caused by municipal wastewaters. The biomass of Scenedesmus strain obtained was harvested and de-oiled. The de-oiled biomass was further used for the adsorptive removal of Reactive red 120 (RR 120) from aqueous solutions. The biomass was treated with H2SO4 and was used in three different forms; free, immobilized and polyaniline composite and all these three different forms of biomass showed adsorption potential of 713.02, 682.52 and 752.68 (mg g−1) respectively. Characterization of biomass was carried out by SEM, FT-IR and pHpzc determination. Kinetic study showed best fitness of pseudo second order kinetic model and experimental data was best fitted with Freundlich adsorption isotherm model. The study results indicated that this strain has good potential for adsorptive removal of contaminants from wastewaters.

Hydrogel applications for adsorption of contaminants in water and wastewater treatment.

During the last decade, hydrogels have been used as potential adsorbents for removal of contaminants from aqueous solution. To improve the adsorption efficiency, there are numerous different particles that can be chosen to encapsulate into hydrogels and each particle has their respective advantages. Depending on the type of pollutants and approaching method, the particles will be used to prepare hydrogels. The hydrogels commonly applied in water/wastewater treatment was mainly classified into three classes according to their shape included hydrogel beads, hydrogel films, and hydrogel nanocomposites. In review of many recently research papers, we take a closer look at hydrogels and their applications for removal of contaminants, such as heavy metal ion, dyes, and radionuclides from water/wastewater in order to elucidate the reactions between contaminants and particles and potential for recycling and regeneration of the post-treatment hydrogels. Graphical abstract ᅟ.

Three-dimensional polylactic acid@graphene oxide/chitosan sponge bionic filter: Highly efficient adsorption of crystal violet dye

Owing to low bearing capacity and efficiency, traditional filters or adsorbents for removal of contaminants like crystal violet (CV) dye required frequent replacement. Besides, the combination of three-dimensional (3D) printing and bionics could break the constraints of traditional configuration. In this study, a novel depth-type hybrid polylactic acid (PLA)@graphene oxide (GO)/chitosan (CS) sponge filter with bionic fish-mouth structure was prepared and fabricated, assisted by 3D printing and double freeze-drying technology, according to the theories of vertical cross-step filtration and swirling flow. And GO/CS sponge and its filtering device were characterized by FITR, SEM, water adsorption and so on. Moreover, it was explained that the impact factors on dye removal mechanism, like GO content (or CS content), contact time, pH, temperature and bionic configuration. As a result, the bionic 3D filtering device demonstrated excellent removal efficiency (97.8±0.5% for CV) and GO/CS sponge exhibited higher strength (74.5±3.5MPa) at the condition of GO content of 9wt%, contact time of 46min, pH of 8 and 35°C, respectively. Therefore, the resulting 3D PLA@GO/CS sponge bionic filter via gravity and vortex driving provided new alternatives for effectively dye-water separation, and it showed great promise for application of biological macromolecules in adsorption.

Selected Adsorbents for Removal of Contaminants from Wastewater: Towards Engineering Clay Minerals

The provision and demand for safe water continues to be a major aspect for governments worldwide as the population continues to grow accompanied by an increase in anthropogenic activities that contaminate water bodies. The common contaminants are the negatively charged ions such as sulfates, positive ions like heavy metals and organic molecules like dyes and phenols. Although, various methods exist for purification of wastewater, the adsorption process is a low cost method that uses readily available adsorbents. Activated carbon, although costly for developing countries, is still the most efficient adsorbent for a variety of substances. However, low cost adsorbents derived from biowaste have being actively explored in water purification. Photocatalytic nanostructured adsorbents not only play a bifunctional role in adsorbing contaminants but also are able to decompose organic pollutants in water using sunlight. The engineering of naturally abundant clay in most developing countries offers an even inexpensive way to clean-up wastewater.

A remarkable adsorbent for removal of contaminants of emerging concern from water: Porous carbon derived from metal azolate framework-6

A series of metal-azolate frameworks or MAFs—MAF-4, -5, and -6—were synthesized and pyrolyzed to prepare porous carbons derived from MAFs (CDM-4, -5, -6, respectively). Not only the obtained carbons but also MAFs were characterized and applied for the adsorption of organic contaminants of emerging concern (CECs, including pharmaceuticals and personal care products) such as salicylic acid, clofibric acid, diclofenac sodium, bisphenol-A, and oxybenzone (OXB) from water. CDM-6 was found to be the most remarkable adsorbent among the tested ones (including activated carbon) for all the adsorbates. OXB was taken as a representative adsorbate for detailed adsorption studies as well as understanding the adsorption mechanism. H-bonding (H-acceptor: CDM; H-donor: CECs) was suggested as the principal mechanism for the adsorption of tested adsorbates. Finally, CDMs, especially CDM-6, were suggested as highly efficient and easily recyclable adsorbents for water purification.

Fabrication and characterization of Fe3O4/CNTs and Fe2N/CNTs composites

By controlling the nitridation temperature, magnetic nanoparticles (Fe3O4and Fe2N) were attached to the carbon nanotubes (CNTs) to fabricate new Fe3O4/CNTs and Fe2N/CNTs composites with magnetic property from the same precursor. The attachment of tiny magnetic nanoparticles on CNTs is crucial for the formation of a homogeneous composite, which provides good combination between CNTs and the magnetic matrix to give a CNT-combined composite. Both Fe3O4/CNTs and Fe2N/CNTs composites show magnetic characteristic from the hysteresis loops measurements at room temperature. Morever, these composites have greater specific surface areas than pure Fe3O4and Fe2N materials, which means that these composites are promising as good adsorbents for removal of contaminants from water and easily seperated from the medium by a magnetic process.

Simulation of biofilter used for removal of air contaminants (ethanol)

Mathematic modeling and simulation of a biofilter system was developed for biofilters filled by three different packing materials such as granular activated carbon (GAC), compost mixed with diatomaceous earth (DE), and compost, respectively, and the effects of biofilter length, packing material, biological activity and the operation time of system on the removal of ethanol (influent contaminant) were studied. The mathematical model for analysis of mass transport phenomena in the biofilter was solved using a two-step, explicit finite difference approximation technique and computer simulation was carried out. The obtained results show that at the early stage of biofiltration the dominant mechanism is adsorption and after saturation of packing by contaminant, biological processes became the dominant mechanism. GAC packed biofilter needs more time to reach to steady state in comparison to the two other packing. GAC is the best adsorbent for contaminant removal; however, compost provides a better environment for microbial growth and activity. The proposed procedure is applicable to analyze the behavior of a biofiltration system used in removal of volatile organic compounds.