Preparation and characterisation of high performing magnesite-halloysite nanocomposite and its application in the removal of methylene blue dye

Novel chitosan/citric acid modified pistachio shell/halloysite nanotubes cross-linked by glutaraldehyde biocomposite beads applied to methylene blue removal

In this study, Cht/PS-CA/HNT biocomposite adsorbent was synthesized using halloysite nanotube as nanomaterial, chitosan which is a biodegradable and biocompatible biopolymer, pistachio shell as biomass source, citric acid as biomass modifier. The removal of methylene blue dyestuff on the synthesized new Cht/PS-CA/HNT from the aqueous medium by adsorption method was investigated. Experimental parameters such as dye concentration, contact time, amount of adsorbent, solution pH and temperature, which affect the adsorption process, were investigated. The adsorption experimental data were analyzed with the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms, which are widely used in aqueous solutions, and it was decided that Langmuir is the most suitable isotherm. The maximum adsorption capacity of the monolayer was calculated to be 111.14 mg/g. Optimum contact time and adsorbent dose were determined as 90 min and 1 g/L. Adsorption experimental data were applied for Pseudo-first-order and Pseudo-second-order kinetic models and it was decided that the most suitable kinetic model was pseudo-second-order. Thermodynamic evaluation of adsorption showed that adsorption is endothermic and adsorption is spontaneous.

Novel fabricated low-cost hybrid polyacrylonitrile/polyvinylpyrrolidone coated polyurethane foam (PAN/PVP@PUF) membrane for the decolorization of cationic and anionic dyes

Dyes are recalcitrait organic pollutants threatening the aquatic environment and human health. In the present study, a novel low-cost hybrid membrane was fabricated by coating polyurethane foam (PUF) with polyacrylonitrile/polyvinylpyrrolidone (PAN/PVP) via phase inversion technique from casting solutions consisting of PAN and PVP with Dimethyl formamide (DMF) and applied for removal of cationic (Methylene Blue (MB)) and anionic (Methyl Orange (MO)) dyes from aqueous solutions. The as-prepared membrane was first characterized by Scan Electron Microscope (SEM), Fourier Transform Infrared (FTIR), Energy Dispersive Spectrometry (EDS), etc. Then, batch experiments were conducted to optimize the adsorption conditions, including contact time, adsorbent dose, dyes concentration, and pH. The dye removal results fitted with pseudo first and second-order kinetics; Langmuir, Freundlich, and Temkin isotherms' models. The maximum dye decolorization was approximately 97% and 95% within 60 and 120 min using 0.5 and 1 g of the fabricated composite for MB and MO, respectively. The kinetic studies showed rapid sorption dynamics following a second-order kinetic model. In addition, dye adsorption equilibrium data fitted well to the Freundlich isotherm with monolayer maximum adsorption capacity of 6.356 and 3.321 mg/g for MO and MB dye, respectively. Thus, the novel hybrid membrane is promising as a cheap and efficient adsorbent for the removal of both cationic and anionic dyes from wastewater. The current study demonstrated a new avenue to achieve efficient management of dyes in aquatic environments.

Surface-Enhanced Biocompatibility and Adsorption Capacity of a Zirconium Phosphate-Coated Polyaniline Composite

The present study deals with the synthesis, characterization, and testing of a novel composite, zirconium(IV) phosphate-coated polyaniline (ZrPO4@PANI), toward the adsorption- and surface-controlled toxicity applications. Following the synthesis of the ZrPO4@PANI composite using the sol-gel route, various characterization techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy, and powder X-ray diffraction were employed to confirm its surface functionality, morphology and agglomeration, and crystallinity and crystal nature, respectively. The composite was found to be effective toward the adsorptive removal of the methylene blue dye (an organic pollutant) as against the changes in the dye concentration, dose, pH, and so forth. Also, to understand the MB adsorption kinetics, the experimental data were evaluated using the Langmuir and Freundlich models and the results were described in accordance with the Langmuir isotherm model (an adsorption capacity of 120.48 mg/g at ambient temperature). In addition, the tests conducted using pseudo-first- and pseudo-second-order kinetic models confirmed the existence of pseudo-second-order rates. Furthermore, the calculation of thermodynamic parameters for the MB adsorption, namely, changes in enthalpy, entropy, and Gibbs' free energy, exhibited a spontaneous, feasible, and exothermic nature. Finally, the comparative studies of in vitro toxicity and flow cytometry confirmed that the copresence of ZrPO4 along with PANI significantly improved the biocompatibility. The outcome of the experimental results implies that the composite is capable enough of serving as the safe and low-cost adsorbent, in addition to supporting the effective capping of the surface toxicity of PANI.

Halloysite Nanoclay with High Content of Sulfonic Acid-Based Ionic Liquid: A Novel Catalyst for the Synthesis of Tetrahydrobenzo[b]pyrans

One of the main drawbacks of supported ionic liquids is their low loading and consequently, low activity of the resultant catalysts. To furnish a solution to this issue, a novel heterocyclic ligand with multi imine sites was introduced on the surface of amino-functionalized halloysite support via successive reactions with 2,4,6-trichloro-1,3,5-triazine and 2-aminopyrimidine. Subsequently, the imine sites were transformed to sulfonic acid-based ionic liquids via reaction with 1,4-butanesultone. Using this strategy, high loading of ionic liquid was loaded on halloysite nanoclay. The supported ionic liquid was then characterized with XRD, SEM, TEM, EDS, FTIR, BET, TGA and elemental mapping analysis and utilized as a metal-free Brønsted acid catalyst for promoting one-pot reaction of aldehydes, dimedone and malononitrile to furnish tetrahydrobenzo[b]pyrans. The catalytic tests confirmed high performance of the catalyst. Moreover, the catalyst was stable upon recycling.

Environmental Remediation of Desalination Plant Outfall Brine Discharge from Heavy Metals and Salinity Using Halloysite Nanoclay

Halloysite (HS) nanoclay was used for the environmental treatment of desalination brine water discharge via the adsorptive removal of selected heavy metals ions; zinc, iron, nickel, and copper, as well as salinity. Different techniques were used for the characterization of the HS nanoclay and it was found that HS nanoclay exists as transparent hollow nanotubes with high surface area. The study showed that most of the heavy metal ions could be removed successfully using the HS nanoclay in a few minutes, at normal conditions. The adsorptive removal of zinc, iron, nickel, and copper, as well as salinity on HS nanoclay was explored kinetically. It was concluded that the pseudo-second-order kinetic model was able to describe the remediation process. In addition, it was found that most of the heavy metals and salinity were removed from the desalination plant outfall brine discharge and the final concentrations were lower than those in the control and standard samples.

Synthesis, Characterization, and Analysis of Hybrid Carbon Nanotubes by Chemical Vapor Deposition: Application for Aluminum Removal

Hybrid carbon nanotubes (CNTs) are grown on biomass powder-activated carbon (bio-PAC) by loading iron nanoparticles (Fe) as catalyst templates using chemical vapor deposition (CVD) and using acetylene as carbon source, under specific conditions as reaction temperature, time, and gas ratio that are 550 °C, 47 min, and 1, respectively. Specifications of hybrid CNTs were analyzed and characterized using field emission scanning electron microscope (FESEM) with energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopic (TEM), Fourier-transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), surface area Brunauer-Emmett-Teller (BET), and zeta potential. The results revealed the high quality and unique morphologies of hybrid CNTs. Furthermore, removal and capacity of Al3+ were optimized by response surface methodology (RSM). However, the results revealed that the pseudo-second-order model well represented adsorption kinetic data, while the isotherm data were effectively fitted using a Freundlich model. The maximum adsorption capacity was 347.88 mg/g. It could be concluded that synthesized hybrid CNTs are a new cost-effective and promising adsorbent for removing Al3+ ion from wastewater.

Surface Modification of Bentonite with Polymer Brushes and Its Application as an Efficient Adsorbent for the Removal of Hazardous Dye Orange I

Poly(2-(dimethylamino)ethyl methacrylate)-grafted bentonite, marked as Bent-PDMAEMA, was designed and prepared by a surface-initiated atom transfer radical polymerization method for the first time in this study. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA) were applied to characterize the structure of Bent-PDMAEMA, which resulted in the successful synthesis of Bent-PDMAEMA. As a cationic adsorbent, the designed Bent-PDMAEMA was used to remove dye Orange I from wastewater. The adsorption property of Bent-PDMAEMA for Orange I dye was investigated under different experimental conditions, such as solution pH, initial dye concentration, contact time and temperature. Under the optimum conditions, the adsorption amount of Bent-PDMAEMA for Orange I dye could reach 700 mg·g-1, indicating the potential application of Bent-PDMAEMA for anionic dyes in the treatment of wastewater. Moreover, the experimental data fitted well with the Langmuir model. The adsorption process obeyed pseudo-second-order kinetic process mechanism.