Hybrid silica aerogel nanocomposite adsorbents designed for Cd(II) removal from aqueous solution

A comparison of adsorption capacity of several synthesis methods of cellulose-based absorbent towards Pb(II) removal: Optimization with response surface methodology

The effects of various synthesis methods of a novel biodegradable magnetically recyclable cellulose-based adsorbent (a magnetized modified silica aerogel) on Pb(II) removal efficiency were studied. QSM (quince seed mucilage) was modified via hydrothermal and ultrasonic modes. Oven-drying and freeze-drying procedures were then used to obtain the final adsorbents. The adsorbents were named A1 to A4 and B1 to B4, depending on the synthesis and drying techniques. XRD, FTIR, BET, and SEM are characterization techniques for identifying the adsorbents. Average crystallite sizes of 15.5, 8.3, 10.9, and 2.7 nm were obtained for A1, A2, A3, and A4 samples (Scherrer formula). SEM image confirmed a Sticky bullets-like morphology. The pHpzc values of 3.4, 6.0, and 4.1 were also determined for Fe-silica aerogel, Fe-QSM, and Fe-silica aerogel-QSM samples. The highest adsorption efficiency of the A2 adsorbent towards Pb(II) cations was followed via the experimental design by the RSM (response surface methodology) approach. ANOVA results showed model F value 185 (>F0.05, 14, 15 = 2.42) and LOF F-value of 0.3831 ( Collapse

Key Words

• Effects of synthesis methods
• Pb(II)-removal
• Quince seed mucilage
• Response surface methodology (RSM)
• Silica aerogel

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MESH Headings

• Cellulose
• Lead
• Adsorption
• Thermodynamics
• Silicon Dioxide
• Kinetics
• Water Pollutants, Chemical/analysis
• Hydrogen-Ion Concentration

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Affiliation(s)

Parastoo Ghahremani Department of Chemical Engineering, Shahreza Branch, Islamic Azad University, P.O. Box 31186145, Shahreza, Isfahan, Iran
Alireza Nezamzadeh-Ejhieh Department of Chemistry, Shahreza Branch, Islamic Azad University, P.O. Box 31186145, Shahreza, Isfahan, Iran.
Mohammad Hassan Vakili Department of Chemical Engineering, Shahreza Branch, Islamic Azad University, P.O. Box 31186145, Shahreza, Isfahan, Iran.

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Strategies to improve membrane performance in wastewater treatment

Membrane technology has rapidly gained popularity in wastewater treatment due to its cost-effectiveness, environmentally friendly tools, and elevated productivity. Although membrane performance in wastewater treatment has been reviewed in several past studies, the key techniques for improving membrane performance, as well as their challenges, and solutions associated with the membrane process, were not sufficiently highlighted in those studies. Also, very few studies have addressed hybrid techniques to improve membrane performance. The present review aims to fill those gaps and achieve public health benefits through safe water processing. Despite its higher cost, membrane performance can result in a 36% reduction in flux degradation. The issue with fouling has been identified as one of the key challenges of membrane technology. Chemical cleaning is quite effective in removing accumulated foulant. Fouling mitigation techniques have also been shown to have a positive effect on membrane photobioreactors that handle wastewater effluent, resulting in a 50% and 60% reduction in fouling rates for backwash and nitrogen bubble scouring techniques. Membrane hybrid approaches such as hybrid forward-reverse osmosis show promise in removing high concentrations of phosphorus, ammonium, and salt from wastewater. The incorporation of the forward osmosis process can reject 99% of phosphorus and 97% of ammonium, and the reverse osmosis approach can achieve a 99% salt rejection rate. The control strategies for membrane fouling have not been successfully optimized yet and more research is needed to achieve a realistic, long-term direct membrane filtering operation.

Research progress and applications of silica-based aerogels - a bibliometric analysis

Silica aerogels are three-dimensional porous materials that were initially produced in 1931. During the past nearly 90 years, silica aerogels have been applied extensively in many fields. In order to grasp the progress of silica-based aerogels, we utilize bibliometrics and visualization methods to analyze the research hotspots and the application of this important field. Firstly, we collect all the publications on silica-based aerogels and then analyze their research trends and performances by a bibliometric method regarding publication year/citation, country/institute, journals, and keywords. Following this, the major research hotspots of this area with a focus on synthesis, mechanical property regulation, and the applications for thermal insulation, adsorption, and Cherenkov detector radiators are identified and reviewed. Finally, current challenges and directions in the future regarding silica-based aerogels are also proposed.

Silica aerogels are three-dimensional porous materials that were initially produced in 1931. During the past nearly 90 years, silica aerogels have been applied extensively in many fields.

Recent Applications of Dual-Stimuli Responsive Chitosan Hydrogel Nanocomposites as Drug Delivery Tools

Polysaccharides are a versatile class of macromolecules that are involved in many biological interactions critical to life. They can be further modified for added functionality. Once derivatized, these polymers can exhibit new chemical properties that can be further optimized for applications in drug delivery, wound healing, sensor development and others. Chitosan, derived from the N-deacetylation of chitin, is one example of a polysaccharide that has been functionalized and used as a major component of polysaccharide biomaterials. In this brief review, we focus on one aspect of chitosan’s utility, namely we discuss recent advances in dual-responsive chitosan hydrogel nanomaterials.

Porous Aerogels and Adsorption of Pollutants from Water and Air: A Review

Aerogels are open, three-dimensional, porous materials characterized by outstanding properties, such as low density, high porosity, and high surface area. They have been used in various fields as adsorbents, catalysts, materials for thermal insulation, or matrices for drug delivery. Aerogels have been successfully used for environmental applications to eliminate toxic and harmful substances-such as metal ions or organic dyes-contained in wastewater, and pollutants-including aromatic or oxygenated volatile organic compounds (VOCs)-contained in the air. This updated review on the use of different aerogels-for instance, graphene oxide-, cellulose-, chitosan-, and silica-based aerogels-provides information on their various applications in removing pollutants, the results obtained, and potential future developments.

Recent Developments in Chitosan-Based Adsorbents for the Removal of Pollutants from Aqueous Environments

The quality of water is continuously under threat as increasing concentrations of pollutants escape into the aquatic environment. However, these issues can be alleviated by adsorbing pollutants onto adsorbents. Chitosan and its composites are attracting considerable interest as environmentally acceptable adsorbents and have the potential to remove many of these contaminants. In this review the development of chitosan-based adsorbents is described and discussed. Following a short introduction to the extraction of chitin from seafood wastes, followed by its conversion to chitosan, the properties of chitosan are described. Then, the emerging chitosan/carbon-based materials, including magnetic chitosan and chitosan combined with graphene oxide, carbon nanotubes, biochar, and activated carbon and also chitosan-silica composites are introduced. The applications of these materials in the removal of various heavy metal ions, including Cr(VI), Pb(II), Cd(II), Cu(II), and different cationic and anionic dyes, phenol and other organic molecules, such as antibiotics, are reviewed, compared and discussed. Adsorption isotherms and adsorption kinetics are then highlighted and followed by details on the mechanisms of adsorption and the role of the chitosan and the carbon or silica supports. Based on the reviewed papers, it is clear, that while some challenges remain, chitosan-based materials are emerging as promising adsorbents.

Microwave-Assisted Synthesis of Hollow Microspheres with Multicomponent Nanocores for Heavy-Metal Removal and Magnetic Sensing

The primary advantage of a hollow structure is the likelihood of introducing diverse components in a single particle to achieve multiple missions. Herein, hollow microspheres with multicomponent nanocores (HMMNs) have been prepared based on a template-free strategy via a microwave-assisted hydrothermal treatment of Chlorella. The resulting HMMNs retain the near-spherical hollow morphology and functional groups of the cell wall of Chlorella, obviating the need for templates and chemical modification. The elements (iron, cobalt, calcium, magnesium, chlorine, and phosphorus) naturally present within the Chlorella cells react to form hydroxyapatite/chlorapatite and magnetic nanocores without the need for exogenous chemical reagents. The performances of HMMNs for cadmium ion (Cd²⁺) removal and antibiotic detection are explored. HMMNs exhibit relatively high adsorbance of Cd²⁺ (1035.8 mmol/kg) and can be easily recovered by application of an external magnetic field. Ion exchange with Ca²⁺ and Mg²⁺ is shown to be the main mechanism of Cd²⁺ elimination. In addition, HMMNs are a suitable carrier for the construction of a magnetic immunosensor, as demonstrated by the successful development of such an immunosensor with acceptable analytical performance for the detection of neomycin in milk samples. The versatile applications of HMMNs result from their multicomponent nanocores, hollow structure, and the functional groups on their shell. This work not only offers a simple and eco-friendly strategy for the fabrication of novel HMMNs but also provides a valuable advanced material for contaminant detection and heavy-metal removal.