Synthesis and characterisation of mineral based composite materials for the remediation of contaminated aqueous solutions

Expanding urbanisation and industrialisation have increased aqueous concentrations of organic contaminants which are toxic to human health and the environment. Hence, remediation of these contaminants from aqueous solutions has become an important environmental concern. This research project aims to synthesize novel mineral-based composite materials, namely diatomite/Fe/Ni, palygorskite/Fe/Ni and sepiolite/Fe/Ni and study their applications for the removal of Orange II and 2,4-dichlorophenol from water. Experimental investigations contain material characterization, batch removal experiments, kinetic studies and contaminant removal mechanisms. Finally, complete removal of the contaminants showed promise of these composite materials for the treatment of organic contaminants from aqueous solutions

Simultaneous adsorption and degradation of 2,4-dichlorophenol on sepiolite-supported bimetallic Fe/Ni nanoparticles

A functional sepiolite-supported Fe/Ni (Sep-Fe/Ni) nanocomposite material synthesised through borohydride reduction method was used to degrade 2,4-dichlorophenol (2,4-DCP) from an aqueous solution. 2,4-DCP was completely removed using Sep-Fe/Ni within 120 min, whereas Fe/Ni or sepiolite in isolation yielded removal efficiencies of 90.8% and 8.4%, respectively. As confirmed by scanning electron microscopy and transmission electron microscopy, sepiolite played a role as the supporting material, which distributed Fe/Ni nanoparticles and significantly diminished their aggregation and correspondingly increased reactivity in adsorption and degradation of 2,4-DCP. The presence of Fe 0 and Ni 0 nanoparticles onto Sep-Fe/Ni was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. The optimized contents of Fe and Ni were 5.19 and 0.51 wt%, respectively which resulted in the higher performance of Sep-Fe/Ni catalyst. The key parameters controlling the degradation of 2,4-DCP such as the initial pH of the solution, catalyst amount and reaction time were systematically explored. Furthermore, Sep-Fe/Ni was shown to exhibit promising capability toward removal of total organic carbon. Kinetic analysis revealed that depletion of 2,4-DCP was consistent with a pseudo first-order kinetic model. The possible adsorption and catalytic degradation mechanism were proposed while the degraded products were identified by chromatographic techniques with ultraviolet and mass spectrometry detection. This study showed the promise of Sep-Fe/Ni as a new environmental pollution management candidate for the remediation of water sources contaminated by chlorophenols

Sepiolite/Fe3O4 composite for effective degradation of diuron

A novel sepiolite-supported Fe3O4 magnetite (SepMag) composite was prepared for diuron degradation. The samples were characterized by X-ray powder diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), N2 adsorption-desorption and BET surface area analysis, scanning electron microscope (SEM) as well as transmission electron microscope (TEM). The chemical state of Fe in SepMag composite before and after degradation experiments was characterized by X-ray photoelectron spectroscopy (XPS). The enhanced degradation efficiency for diuron was attributed to the effective generation of hydroxyl radical in ultrasound/SepMag/H2O2 system. The degradation rate of diuron depended upon the composite amount, hydrogen peroxide dosage, initial pH of solution and temperature. The degradation reaction was also optimized by changing the ultrasound intensity and Fe3O4 content in the composites. Moreover, mineralization and degradation pathway were evaluated on the basis of total organic carbon and liquid chromatography mass spectrometry. It was confirmed that with the assistance of ultrasound treatment SepMag composite has potential advantages for the removal of diuron from aqueous solution

Degradation of 2,4-dichlorophenol using palygorskite-supported bimetallic Fe/Ni nanocomposite as a heterogeneous catalyst

A functional palygorskite-supported Fe/Ni (Pal-Fe/Ni) nanocomposite material is synthesised to remove 2,4-dichlorophenol (2,4-DCP) in an aqueous solution. The hypothesis is that Pal-Fe/Ni has superior efficacy than other Fe materials, such as Pal-Fe and Fe/Ni with regard to 2,4-DCP removal even though it requires less loading amount of metallic influencing the reaction. The surface morphology and surface chemical environments of Pal-Fe/Ni are studied using SEM, TEM, XRD and XPS characterisation methods. As revealed from batch experiments, initial pH, sample amount and reaction time are the key parameters influencing the 2,4-DCP removal efficiency. A further experiment reveals that iron leaching plays a main role for 2,4-DCP removal. Kinetic study reveals that removal of 2,4-DCP can be described by pseudo first-order model. A synergistic adsorption and catalytic reduction mechanism for the removal of 2,4-DCP by Pal-Fe/Ni is studied using UV-Vis, total organic carbon and HPLC-MS analyses. The results reveal complete dechlorination and 2,4-DCP degradation together with high total organic carbon removal. This study on immobilising Fe/Ni bimetallic nanoparticles onto palygorskite creates a new prospect for the practical application of Pal-Fe/Ni nanocomposite in remediation of contaminated aqueous solutions

A performance evaluation of a new iron oxide-based porous ceramsite (IPC) in biological aerated filters

<p>A novel medium containing iron oxide-based porous ceramsite (IPC) and commercial ceramsite (CC) was used in two laboratory-scale upflow biological aerated filters (BAFs) to treat city wastewater to compare their efficacy in wastewater treatment. The IPC BAF and CC BAF were operated in water at 20–26°C, an air/water (A/W) ratio of: 3:1 and hydraulic retention times (HRTs) of 7, 3.5, 1.75, and 0.5 h and the removal of ammonia nitrogen (NH₃–N), total nitrogen (TN), total organic carbon (TOC), and phosphorus (P) were studied. Our results indicated that IPC BAF was superior to CC BAF in terms of TOC, TN, NH₃–N, and P removal. IPC had higher total porosity and larger total surface area than CC. The interconnected porous structure of IPC was suitable to microbial growth, protozoan, and metazoan organisms were primarily found in the accumulated biofilm layer. Biomass, in the biofilm layer, was detected at three distinct distances (300, 900, and 1500 mm) from the bottom of the inlet filter, again indicating that the IPC was more suitable for biomass growth. The presence of biomass improves the simultaneous removal efficiency of nitrogen and phosphorus in the IPC BAF. Thus, our findings support IPC as a material for use in filter media in wastewater treatment BAFs.</p

Clay-supported nanoscale zero-valent iron composite materials for the remediation of contaminated aqueous solutions: A review

Highlights - A review of contaminants removed by clay-nZVI composite materials from aqueous solutions is made. - Reaction mechanisms of the materials with contaminants are discussed. - Excellent removal efficiencies of contaminants by composite materials are reported. - The review suggests research needs for future work. Abstract Recent industrialization and urbanization have increased the aqueous concentrations of a wide range of contaminants, which are toxic to human health and the environment. Therefore, remediation of aqueous solutions has turned into an important environmental issue. Over the last decade, growing attention has been paid to clay-supported nanoscale zero-valent iron (nZVI) composite materials as efficient and promising remediation materials in wastewater treatment and groundwater remediation technologies. This paper gives an overview of the clay minerals, zero-valent iron materials, clay-supported nZVI composites, and progress obtained during the remediation of contaminated aqueous solutions utilizing the clay-supported nZVI composites for the removal of heavy metals, nitrate, selenate, dyes, phenolic compounds, chlorinated organic compounds, nitroaromatic compounds and polybrominated diphenyl ethers. Reaction mechanisms and removal efficiencies were studied and evaluated. It was reported that the clay-supported nZVI composites have appreciable removal efficiency for different types of contaminants. This paper also reviews the use of ZVI-clay technology for the remediation of contaminated sites. Concerning clay-supported nZVI composites for future research, some recommendations are proposed and conclusions are drawn

Catalytic degradation of Orange II in aqueous solution using diatomite-supported bimetallic Fe/Ni nanoparticles

A functional diatomite-supported Fe/Ni nanocomposite successfully remediated Orange II contaminant in aqueous solution. The hypothesis was that diatomite-supported Fe/Ni would not only be more effective than Fe/Ni but also require less metallic loading to effect the catalytic reaction. Batch experiments indicate that 99.00% of Orange II was removed using diatomite-supported Fe/Ni, while only 86.64 and 3.59% of Orange II were removed using bimetallic Fe/Ni nanoparticles and diatomite, after 6 h of reaction, respectively. Characterisation by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) indicates that the use of diatomite as a support material reduced the aggregation of bimetallic Fe/Ni nanoparticles, thereby resulting in an enhancement in the reactivity. A synergistic mechanism for the removal of Orange II by diatomite-supported Fe/Ni was proposed which involves adsorption, followed by catalytic reduction. This study has demonstrated that diatomite may be a suitable support material for stabilizing and dispersing bimetallic Fe/Ni nanoparticles and the resulting diatomite-supported Fe/Ni composite could be a promising catalyst for the remediation of dye-contaminated wastewater