Wastewater Treatment Using Membrane Technology

Water contamination by heavy metals, cyanides and dyes is increasing globally and needs to be addressed as this will lead to water scarcity as well as water quality. Different techniques have been used to clean and renew water for human consumption and agricultural purposes but they each have limitations. Among those techniques, membrane technology is promising to solve the issues. Nanotechnology present a great potential in wastewater treatment to improve treatment efficiency of wastewater treatment plants. In addition, nanotechnology supplement water supply through safe use of modern water sources. This chapter reviews recent development in membrane technology for wastewater treatment. Different types of membrane technologies, their properties, mechanisms advantages, limitations and promising solutions have been discussed

Electrocatalytic sensor devices: (I) cyclopentadienylnickel(II) thiolato Schiff base monolayer self-assembled on gold

The fabrication of a self-assembled monolayer (SAM) of a cyclopentadienylnickel(II) thiolato Schiff base compound, [Ni(SC6H4NC(H)C6H4OCH2CH2SMe)(η5-C5H5)]2 on a gold electrode is described. Effective electronic communication between the Ni(II) centres and the gold surface was established by electrochemically cycling the Schiff base-doped Au electrode in 0.1 M NaOH from −200 mV to +600 mV. The SAM-modified electrode exhibited quasi-reversible electrochemistry. The integrity of this electrocatalytic SAM, with respect to its ability to block and electro-catalyse certain Faradaic processes, was interrogated using cyclic voltammetric experiments. The formal potential, E°′, varied with pH to give a slope of about −30 mV pH−1. The surface concentration, G, of the nickel redox centres was found to be 1.548×10−11 mol cm−2. By electrostatically doping the SAM using an applied potential of +700 mV versus Ag/AgCl, in the presence of horseradish peroxidase (HRP), it was fine-tuned for amperometric determination of H2O2. The electrocatalytic-type biosensor displayed typical Michaelis–Menten kinetics and the limit of detection was found to be 6.25 mM

Fabrication and Assessment of ZnO Modified Polyethersulfone Membranes for Fouling Reduction of Bovine Serum Albumin

ZnO/PES composite membranes were fabricated by phase inversion method using DMAc as a solvent. The structure of ZnO was investigated using TEM, SEM, XRD, and TGA. TEM images of ZnO nanoparticles were well-defined, small, and spherically shaped with agglomerated nanoparticles particles of 50 nm. The SEM and XRD results were an indication that ZnO nanoparticles were present in the prepared ZnO/PES composites membranes. Contact angle measurements were used to investigate surface structures of the composite membranes. The amount of ZnO nanoparticles on PES membranes was varied to obtain the optimal performance of the composite membranes in terms of pure water flux, flux recovery, and fouling resistance using the protein bovine serum albumin (BSA) as a model organic foulant. The results showed that addition of ZnO to PES membranes improved the hydrophilicity, permeation, and fouling resistance properties of the membranes. Pure water flux increased from a low of 250 L/m2h for the neat membrane to a high of 410 L/m2h for the composite membranes. A high flux recovery of 80–94% was obtained for the composite membranes. The optimal performance of the composite membranes was obtained at 1.5 wt% of ZnO

Electrocatalytic sensor devices: (I) cyclopentadienylnickel(II) thiolato Schiff base monolayer self-assembled on gold

The fabrication of a self-assembled monolayer (SAM) of a cyclopentadienylnickel(II) thiolato Schiff base compound, [Ni(SC6H4NC(H)C6H4 OCH2CH2SMe)( 5-C5H5)]2 on a gold electrode is described. Effective electronic communication between the Ni(II) centres and the gold surface was established by electrochemically cycling the Schiff base-doped Au electrode in 0.1 M NaOH from −200 mV to +600 mV. The SAM-modified electrode exhibited quasi-reversible electrochemistry. The integrity of this electrocatalytic SAM, with respect to its ability to block and electro-catalyse certain Faradaic processes, was interrogated using cyclic voltammetric experiments. The formal potential, E◦ , varied with pH to give a slope of about −30 mV pH−1. The surface concentration, G, of the nickel redox centres was found to be 1.548 × 10−11 mol cm−2. By electrostatically doping the SAM using an applied potential of +700 mV versus Ag/AgCl, in the presence of horseradish peroxidase (HRP), it was fine-tuned for amperometric determination of H2O2. The electrocatalytic-type biosensor displayed typical Michaelis–Menten kinetics and the limit of detection was found to be 6.25 mM. © 2004 Elsevier B.V. All rights reserved

Influence of the Zeolite ZSM-22 Precursor on a UF-PES Selective Substrate Layer for Salts Rejection

Fabrication of the ZSM-22/Polyethersulfone (ZSM-22/PES) membranes as selective salt filters represent a growing membrane technological area in separation with the potential of high economic reward based on its low energy requirements. The incorporation of ZSM-22 zeolite material as additives into the PES polymer matrix has the prospective advantage of combining both the zeolite and polymer features while overcoming the limitations associated with both materials. This work investigated the influence of the nature of the silica precursor on ZSM-22 zeolite hydrothermally synthesised using colloidal (C60) and fumed (C60) silica to Si/Al of 60. The successful synthesis of the highly crystalline zeolitic materials was confirmed through XRD, FTIR, and SEM with EDX. The ZSM-22 additives were directly dispersed into a PES polymeric matrix to form a casting solution for the preparation of the ZSM-22/PES selective substrate layers via a phase inversion method for salts rejection. The polymeric PES was selected as an organic network in which the content of the ZSM-22 zeolite (ranging between 0 and 1.0 wt.%), was obtained and characterised by XRD, FTIR, and SEM analysis, as well as water contact angle (WCA) measurement and dead-end filtration cell. The phase inversion preparation method has induced the resulting ZSM-22/PES NF substrates anisotropy, as attributed to a high water flux to the above 700 L·m−2·h−1; high selectivity and rejection of salts to above 80% is revealed by the obtained results. The materials also exhibited improved antifouling behavior to above 70% flux recovery ratios. As such, the nature of the silica precursor influences ZSM-22 zeolite synthesis as a potential additive in the PES polymer matrix and led to the enhanced performance of the pure PES ultrafiltration membrane

Recovery of Palladium and Gold from PGM Ore and Concentrates Using ZnAl-Layered Double Hydroxide@zeolitic Imidazolate Framework-8 Nanocomposite

Gold (Au) and palladium (Pd) are platinum group metals (PGMs) that are considered critical in society because they are required in several industrial applications. Their shortage has caused the urgent need for their recovery from secondary resources. Therefore, there is a need to develop functional materials with high adsorption capacity and selectivity for recovery of PGMs from various secondary sources. In this study, a Zn-Al-layered double hydroxide@zeolitic imidazolate framework-8 (Zn–Al–LDH@ZIF–8) nanocomposite was used as an adsorbent for the recovery of Au and Pd from ore concentrates. The Zn–Al–LDH@ZIF–8 nanocomposite was characterised using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, zeta potential, and X-ray diffraction (XRD) spectroscopy. The recovery of Au(III) and Pd(II) was achieved using ultrasound-assisted dispersive µ-solid-phase extraction (UA-D-µ-SPE) and their quantification was attained using an inductively coupled plasma mass spectrometer (ICP-MS). The results showed that the surface of the adsorbent remained positively charged in a wide pH range, which endowed the nanocomposite with high adsorption affinity towards Au(III) and Pd(II). Under optimised conditions, the equilibrium studies revealed that the adsorption of Au(III) and Pd(II) ions followed the Langmuir isotherm model with maximum sorption capacities of 163 mg g−1 and 177 mg g−1 for Au(III) and Pd(II), respectively. The nanocomposite possessed relatively good regeneration, reusability, and stability characteristics, with its performance decreasing by only 10% after five adsorption–desorption cycles

Bimetallic nickel complexes with bridging dithiolato Schiff base ligands: synthesis, mass spectral characterisation and electrochemistry

Schiff base dithiols with thiophene or phenyl linkers were prepared from condensation of the dialdehydes 2,5-(OHC)₂C₄H₂S, 1,3-(OHC)₂C₆H₄, 1,4-(OHC)₂C₆H₄ and 1,4'-(OHC)₂(C₆H₄)₂ with 4-H₂NC₆H₄(SH). The Schiff base dithiols readily reacted with Ni( ⁵-C₅H₅)(PR₃)Br (R=Bu or Ph) in the presence of Et₃N to form bimetallic complexes ( ⁵-C₅H₅)(PR₃)Ni&unknown;SC₆H₄N&unknown;C(H)ArC(H)&unknown;NC₆H₄S&unknown;Ni(PR₃)( ⁵-C₅H₅) (Ar=C₄H₂S (6), 1,3-C₆H₄ (7), 1,4-C₆H₄ (8), 1,4'-(C₆H₄)₂ (9). The bimetallic nature was established from elemental analysis and mass spectrometry. Cyclic voltammetry of complexes 6, 8 and 9 are indicative of electronic communication between the nickel centres via the bridging dithiolato Schiff base ligands

An In Situ Incorporation of Acrylic Acid and ZnO Nanoparticles into Polyamide Thin Film Composite Membranes for Their Effect on Membrane pH Responsive Behavior

This paper focuses on an in situ interfacial polymerization modification of polyamide thin film composite membranes with acrylic acid (AA) and zinc oxide (ZnO) nanoparticles. Consequent to this modification, the modified polyamide thin film composite (PA–TFC) membranes exhibited enhanced water permeability and Pb (II) heavy metal rejection. For example, the 0.50:1.50% ZnO/AA modified membranes showed water permeability of 29.85 ± 0.06 L·m−2·h−1·kPa−1 (pH 3), 4.16 ± 0.39 L·m−2·h−1·kPa−1 (pH 7), and 2.80 ± 0.21 L·m−2·h−1·kPa−1 1 (pH 11). This demonstrated enhanced pH responsive properties, and improved water permeability properties against unmodified membranes (2.29 ± 0.59 L·m−2·h−1·kPa−1, 1.79 ± 0.27 L·m−2·h−1·kPa−1, and 0.90 ± 0.21 L·m−2·h−1·kPa−1, respectively). Furthermore, the rejection of Pb (II) ions by the modified PA–TFC membranes was found to be 16.11 ± 0.12% (pH 3), 30.58 ± 0.33% (pH 7), and 96.67 ± 0.09% (pH 11). Additionally, the membranes modified with AA and ZnO/AA demonstrated a significant pH responsiveness compared to membranes modified with only ZnO nanoparticles and unmodified membranes. As such, this demonstrated the swelling behavior due to the inherent “gate effect” of the modified membranes. This was illustrated by the rejection and water permeation behavior, hydrophilic properties, and ion exchange capacity of the modified membranes. The pH responsiveness for the modified membranes was due to the –COOH and –OH functional groups introduced by the AA hydrogel and ZnO nanoparticles

Fabrication and performance evaluation of tannin iron complex (TA-FeIII/PES) UF membrane in treatment of BTEX wastewater

Oil exploration generates produced water that is characterized as hazardous and toxic waste. Produced water contains a mixture of various pollutants, including monoaromatic hydrocarbons BTEX (benzene, toluene, ethylbenzene, and xylene), compounds that are carcinogenic even in small concentrations.  In this study, tannin iron complex (TA-FeIII), blended into polyethersulfone (PES) membrane was evaluated for the treatment of BTEX-containing wastewater. The membranes were fabricated using the non-solvent induced phase separation (NIPS) method and loading of the TA-FeIII complex on the membranes varied from 0–0.9 wt%. The fabricated membranes were characterized using various techniques such as scanning electron microscopy (SEM), water contact angle (WCA), Fourier transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM) to check the surface morphology, hydrophilicity, surface functionality and surface roughness of the fabricated membranes, respectively. The TA-FeIII modified membranes showed increased pure water flux from 100 (PES 0) to ∼150 (PES 0.9) L/(m2‧h) at 100 kPa. The performance of the fabricated membranes was tested using 70 mg/L synthetic BTEX solution. Overall BTEX rejection > 70% was achieved at increasing TA-FeIII loadings compared to BTEX rejection < 65% for the pure PES membrane. Rejection of the BTEX compounds was mainly through the size exclusion mechanism. These modified TA-FeIII/PES UF membranes proved to be effective in the treatment of BTEX-containing water, and also have the potential to be applied in oily wastewater treatment.&nbsp

Low-Cost High Performance Polyamide Thin Film Composite (Cellulose Triacetate/Graphene Oxide) Membranes for Forward Osmosis Desalination from Palm Fronds

Novel low-cost cellulose triacetate-based membranes extracted from palm fronds have been fabricated through the phase–inversion procedure. The cellulose tri-acetate (CTA) membrane was modified by incorporation of graphene oxide (GO) prepared from palm fronds according to the modified Hummer method as well as the preparation of polyamide thin film composite CTA membranes to improve forward osmosis performance for seawater desalination. The surface characteristics and morphology of the prepared CTA, GO, and the fabricated membranes were investigated. The modified TFC prepared membrane had superior mechanical characteristics as well as permeation of water. The performance of the prepared membranes was tested using synthetic 2 M Sodium chloride (NaCl) feed solution. The water flux (Jw) of the thin-film composite (TFC) (CTA/0.3% GO) was 35 L/m2h, which is much higher than those of pure CTA and CTA/0.3% GO. Meanwhile, the salt reverse flux TFC (CTA/0.3% GO) was 1.1 g/m2h), which is much lower than those of pure CTA and CTA/0.3%. GO (Specific salt flux of TFC (CTA/0.3% GO) substrate membrane was 0.03 g/L indicating good water permeation and low reverse salt flux of the TFC membrane compared to CTA. A real saline water sample collected from Hurgada, Egypt, with totally dissolved solids of 42,643 mg/L with NaCl as the draw solution (DS) at 25 °C and flow rate 1.55 L/min, was used to demonstrate the high performance of the prepared TFC membrane. The chemical analysis of desalted permeated water sample revealed the high performance of the prepared TFC membrane. Consequently, the prepared low-cost forward osmosis (FO) thin-film composite CTA membranes can be introduced in the desalination industry to overcome the high cost of reverse osmosis membrane usage in water desalination