Papers by Keyword: Water Treatment

Abstract: In this study, the magnetic UiO-66 composite was prepared and used as an adsorbent to effectively remove Rhodamine B (RhB) from water. The as-prepared magnetic MOFs composites not only retain the unique structure and properties of MOFs materials, but also can be quickly recovered and separated from aqueous solution by applying a magnetic field. The effects of contact time, initial concentration on the adsorption properties were studied. For RhB, pseudo-second-order model and Langmuir model could well explain the adsorption process of magnetic UiO-66 composite, indicating that the adsorption process of the RhB was mainly performed by chemisorption on uniform surface, and the maximum adsorption capacity is 188.68 mg/g. The possible mechanism for RhB was further proposed, revealing that electrostatic interactions, π-π stacking interactions mainly affected the adsorption process.

Abstract: Pyrene is a ubiquitous, persistent, and mutagenic pollutant that belongs to the polycyclic aromatic hydrocarbons. Graphitic carbon nitride (g-C₃N₄) has emerged as a promising photocatalyst for degradation of various pollutants in water and wastewater treatment due to its unique band structure and excellent physiochemical stability. This paper presents the comparative study of composites g-C₃N₄ from various combinations of precursors using thermal polycondensation at 600 °C. Comparative experiments revealed that the preparation conditions of both precursors and the mass ratios of precursor influenced the overall performance of photocatalyst during photocatalytic degradation of pyrene. Experimental results indicated that the best performance of composites g-C₃N₄t photocatalyst was prepared from a wet mixture of dicyandiamide and guanidine carbonate precursors at a mass ratio of 1:1 with 43.9 % pyrene degradation under visible light irradiation for 240 mins. The reusability of the best g-C₃N₄ composites for the photocatalytic degradation of pyrene was also investigated. It was found that the prepared photocatalyst was stable up to five cycles of photocatalysis. Meanwhile, holes (h⁺) and hydroxyl radicals (·OH) were identified as the primary and secondary dominant reactive species in the photocatalytic degradation through scavenging trapping experiments.

Abstract: Nowadays, the excessive and uncontrolled discharge of chemicals are imposing major health threats. The demands for clean and safe water amplifies the need to develop improved technologies for environmental contaminant removal. Considering the limitations of conventional methods for contaminants removal, we have prepared magnetic iron oxide nanoparticles functionalised with reduced graphene oxide as a potential material for environmental pollutants removal. The magnetic properties in potential adsorbent materials are highly desirable due to several advantages. Among which are their large adsorptive surface area, low diffusion resistance, high adsorption capacity and fast separation in large volumes of solution. The surface functionalised magnetic iron oxide nanoparticles (MNP) were fabricated using a one-pot hydrothermal method by adding reduced graphene oxide (rGO) into the reaction system. The graphene oxide were reduced prior to the addition in the hydrothemal decomposition step. The resultant rGO-MNP nanocomposites were characterised using FT-IR, SEM and VSM to investigate the functional groups, morphology and magnetic properties, resepectively. We also demonstrated the potential of the hybridised magnetic material with hydrophobic reduced graphene oxide for environmental pollutant removal.

Abstract: The advancement of 3D printing in the past few decades propelled many ground-breaking developments in the water treatment industry. More specifically, 3D printing has the unique advantage of prototyping parts of high complexity with acute precision within a short period of time. Innovative feed spacers and membranes, which could not be fabricated using conventional methods, can now be 3D printed and evaluated in actual filtration experiments. However, there are still limitations to 3D printing such as the printing resolution, build volume and printing speed which poses some problems, especially in the fabrication of membranes. This paper presents a comprehensive and critical discussion on the 3D printed feed spacer and membrane prototypes from a 3D printing perspective.

Abstract: Plastic, a non-biodegradable material has always been a concern to the environment and people. This single-use item generates waste to landfills and it persists for centuries once disposed. The urge of transforming such material into a highly valuable product has sought attention from many researchers. This study emphasizes on a nanotechnological approach to synthesize vertically-aligned carbon nanotubes (CNTs) on a substrate template using commercially available plastic bags as carbon precursor. CNTs are grown inside a hexagonally arranged nanoporous anodic alumina membranes (NAAMs). CNTs are liberated by wet chemical etching to dissolve the alumina matrix. The resulting CNTs are used as adsorption media filters for water treatment purpose. The high adsorption affinity towards heavy metals, organic matters and microbes, ability to antifouling and self-cleaning function have made CNTs a better choice over others. This article briefly discusses the catalyst-free synthesis, growth mechanism, characterization and functionalization of CNTs for water treatment application.

Abstract: This study presents the results of modifications done to cellulose acetate (CA) membranes intended for filtration purposes using organo-montmorillonite (O-MMT) clay. The researchers incorporated O-MMT with CA to synthesize composite CA/O-MMT membranes via hand casting. The produced membranes were then characterized to determine the effect of O-MMT of varying % wt. concentrations to its surface morphology and wettability. Morphology of the membranes were observed under a Scanning Electron Microscope (SEM), while its wettability was accounted for by subjecting the samples to contact angle and porometer analysis. SEM images revealed that the presence of O-MMT generally affects the membrane’s surface roughness while the pore size test results show that increasing the concentration of O-MMT leads to a larger average pore size. Conductivity test data suggest that though becoming less hydrophilic, the modified membranes still hold efficient in removing the salt ions from the solution and that the amount of O-MMT concentration present in the CA/O-MMT membranes is the main determining factor behind its efficacy for ion adsorption.

Abstract: In this study, a local mineral clay was used as an adsorbent for the elimination of a cationic dye: methylene blue (MB), in an aqueous solution by adsorption technique. Early on, we performed mineralogical and textural analyses of a clay sample using various techniques, namely X-ray diffraction, Brunauer-Emmett-Teller analysis and Fourier-transform infrared spectroscopy. The experimental results showed that this adsorbent is a mesoporous and non-swelling clay with illite and kaolinite as the major components with a specific area of about 110m²/g. The study of MB adsorption on the clay was carried out by optimizing the conditions of adsorption, notably the initial concentration of pollutant C₀, the mass of clay m, the contact time t, the potential of hydrogen of the solution pH and the temperature T. Experimental results have shown that the equilibrium data are well adjusted by a Langmuir isotherm equation. Thermodynamic parameters such as the changes in Gibbs free energy, enthalpy, and entropy were determined from batch experiments. Results revealed that the adsorption of MB onto illitic clay was endothermic and spontaneous process. Kinetic modeling was also carried out. Experimental data adjusted the kinetic model of pseudo-second order with two stages of intraparticle diffusion.

Abstract: PANI was prepared in-house, characterized and utilized in the sorption of calcium, magnesium, iron, and copper in aqueous solution. The objective of this research was to evaluate adsorption of metals in mono and multi-metal in aqueous solutions onto PANI. Literature has it that, there is no record for competitive sorption of metals by PANI. The characterization of the prepared PANI confirmed with other literature that it was the Emeraldine PANI that was prepared. The results obtained after the multi metal adsorption experiment showed that PANI has a good performance in the removal of copper, iron, calcium, and magnesium, and can be credited to its' large surface area since it is a nanomaterial. Testing for the selectivity showed that the prepared nanoPANI adsorbed 95.2% of lead, 93.8% of copper and 75.8% of the iron in the single metal system.

Abstract: The nitrification process inside the water treatment facilities is an environmental threat because it might cause unacceptable concentrations of nitrites in drinking water. Special data processing has been carried out in the course of daily monitoring of concentration levels for ammonium, nitrogen, nitrites, and nitrates in the Siverskyi Donets river at the water intake site, and downstream, in the water mass having passed through the facilities of the water treatment complex "Donets". Based on the above studies, a positive correlation was revealed (with a correlation coefficient of 0.64-0.93) between the activity of nitrification processes in the natural reservoir and the activity of nitrification inside the water treatment facilities. The environmental outcomes of the nitrification processes inside the water treatment facilities might be dangerous. Experimental studies have proven that the zeolite backfill of the rapid filters installed at the water treatment complex is the most favorable medium for immobilization of the nitrifying bacteria in comparison with other backfills of silica sand or anthracite coal, therefore it is quite suitable for the development of nitrification process. The studies have shown that nitrites do not accumulate in water after water treatment procedures, therefore, the rate of phase I nitrification inside these facilities does not exceed the rate of the second phase. To clean the filtering backfill of these microorganisms, a conventional technological wash is fairly enough.

Abstract: Natural clays, engineered Ag-nanoparticles (NP), TiO₂-NP, and exhausted coffee grounds were used to synthesize a nanocomposite 7NC using a Vertisol soil through a single-step by thermal method, to build a nanomaterial to degrade or filtrate pollutants from soils, water or air. The surface characteristics and the porosity of the composite were studied through nitrogen gas adsorption at liquid nitrogen temperature and application of the Brunauer–Emmett–Teller (BET) equation and the results indicated that the microporous composites ranged a surface area of 17.36 m² g^-1. X-ray diffraction showed crystalline structure and crystalline phase of the nanocomposites. HR-TEM-STEM results demonstrated that TiO₂-NP surrounded Ag-NP, and both were impregnated on natural soil nanoparticles. Oxidation states of the Ag-NP and TiO₂-NP were analyzed by X-ray photoelectron spectroscopy (XPS) The energy gap of nanocomposite 7NC was determined using the Kubelka-Munck model from Ultraviolet–visible diffuse reflectance (UV–Visible DRS) spectra. The photocatalytic activity of these nanocomposites was evaluated, and the results indicated that nanocomposite with Vertisol-soil-NP (7NC) degraded the harmful organic compound methylene blue (MB) while the antimicrobial activity and resistance against Escherichia coli and Staphylococcus aureus and the zone of inhibition (ZOI) also were analyzed. The nanocomposites Ag-NP/TiO₂-NP/natural-soil-NP/exhausted coffee-ground showed its for the development of an efficient material for environmental remediation with photocatalytic and antimicrobial activity.