Zulfiqar Ahmad Rehan

The effect of cerium alteration on the photocatalytic performance of WO3 in sunlight exposure for water decontamination

In an effort to enhance the photocatalytic activity of cubic WO3 in sunlight exposure, its surface was modified by impregnating the Ce3+ ions ranging from 1% to 25% with a step of 5% with respect to the weight of WO3. Compared to pure WO3, the optical analysis by diffuse reflectance spectroscopy (DRS) revealed better absorption cross-section and red shift in the band edges for Ce loaded catalysts. The decreased intensity of photoluminescence (PL) emissions and the suppression of the Raman active bands of WO3 verified the recombination quenching ability of Ce surface states. The XRD analysis revealed the existence of Ce3+ states in the lower loadings (≤5%), whereas the majority of Ce4+ states were noticed at higher loadings. The FESEM analysis also verified the formation of individual particles of Ce(III,IV) oxides at the surface of WO3 at higher loadings. The XPS analysis of 10% Ce loaded samples also revealed the presence of mixed oxides of Ce at higher loading. Except for 1% Ce loaded WO3, the estimation of charge–discharge capacity, in comparison to pure WO3, revealed the enhancement in the charge retention ability with the increasing Ce loading. In comparison to pure WO3, the synthesized catalysts exhibited superior activity for the removal of 2-nitrophenol and 2-chlorophenol substrates in natural sunlight exposure. The analysis of the degradation data revealed that in the lower concentration the surface oxygen bonded Ce3+ states serve as electron trapping and transfer centers, whereas with the increasing surface density the synergic composite mechanism is the dominating mode. The exaggerated estimation in the EDX analysis of the samples loaded with 15% and 20% Ce also revealed the major surface coverage by the oxides. The salient feature of the study was the evaluation of the photocatalytic activity with the minimal catalyst loading of 350 mg L−1.

Marinobacter lipolyticus from Red Sea for lipase production and modulation of silver nanomaterials for anti-candidal activities

In this study, the bacterial strain CEES 33 was isolated from the coastal area of the Red Sea, Jeddah, Kingdom of Saudi Arabia. The bacterium isolate was identified and characterized by using biochemical and molecular methods. The isolate CEES 33 has been identified as Gram-negative rod shaped and cream pigmented spherical colonies. It also demonstrated a positive result for nitrate reduction, oxidase, catalase, citrate utilization, lipase and exopolysaccharide production. Strain CEES 33 was characterized at the molecular level by partial 16S rRNA sequencing and it has been identified as Marinobacter lipolyticus (EMBL|LN835275.1). The lipolytic activity of the isolate was also observed 2.105 nkatml-1. Furthermore, the bacterial aqueous extract was used for green synthesis of silver nanoparticles (AgNPs), which was further confirmed by UV-visible spectra (430 nm), XRD and SEM analysis. Moreover, the biological functional group that involved in AgNPs synthesis was confirmed by FTIR spectra. The biological activities of AgNPs were also investigated, which showed a significant growth inhibition of Candida albicans with 16 ± 2 mm zone of inhibition at 10 μg dose/wells. Therefore, bacterium Marinobacter lipolyticus might be used in future for lipase production and nanoparticles fabrication for biomedical application, to control fungal diseases caused by C. albicans.

Polyethersulfone membrane printed with 1-(2-pyridylazo)-2-naphthol (PAN) sensor for sensitive enrichment and rapid determination of Zn2+ in water

A facile approach for the rapid and sensitive detection as well as determination of Zn2+ ions in water has been developed. The method was based upon the use of a polyethersulfone membrane printed with 1-(2-pyridylazo)-2-naphthol (PAN) as a novel platform for rapid enrichment of Zn2+ ions. Atomic force microscopy, scanning electron microscopy and goniometer studies were performed to understand the PES characteristics. The end result for Zn2+ determination was visually noticeable via a distinct colour change on the membrane surface from 10−3 μg mL−1 onwards, with a linear dynamic range of 10−1 to 102 μg mL−1. The specificity of the proposed sensor was improved by masking common interfering ions towards Zn2+ in water. The developed platform is robust enough to withstand slight changes in pH, temperature and volume, confirming its applicability in point-of-use testing. The proposed membrane-based sensor provides better performance compared to the similar assay executed on a pristine filter-paper platform with a maximum limit of detection of only up to 101 μg mL−1. The developed sensor was satisfactorily applied for the analysis of Zn2+ ions in tap- and wastewater samples without pretreatment with an acceptable relative standard deviation (RSD) ≤ ±2.9%. The precision of the proposed method was also estimated for inter- and intra-day replicates (n = 5) at various concentrations and RSD values of less than 11.0% were achieved. Statistical treatment using t- and F-tests of the results of the developed sensor with those obtained by the standard method reflected no significant differences in the precision.

A Highly Structured 1,10-Phenanthroline Arrayed Hydrophobic Sulfone Membrane Platform for the Rapid Determination and Speciation of Fe2+/Fe3+ Ions in Water

An optical assay for the rapid determination and chemical speciation of Fe2+/Fe3+ species has been proposed for the first time on a polyether sulfone (PES) membrane platform. The small pore size and low wettability (θ ∼82°) of the membrane disallowed the dissipation of analyte droplets on the surface, thus localizing it onto nanoliter arrayed 1,10-phenanthroline spots. Under optimized conditions and within ∼5 min, an acceptable limit of detection (0.1 μg mL-1) and linear dynamic range (1 - 100 μg mL-1) were achieved. The proposed method was also successfully applied for indirect determination of Fe3+ ions in synthetic samples after reduction to Fe2+ using SO2. The performance of the proposed sensor was validated for its robustness and stability. Due to high selectivity and accuracy, the method was satisfactorily applied for the analysis of Fe2+/Fe3+ species in marine water samples. The proposed method is an easy and low-cost system coupled with good reproducibility and ruggedness, applicable for point-of-use testing.

Synthesis and Characterization of Silver Nanoparticles-Filled Polyethersulfone Membranes for Antibacterial and Anti-Biofouling Application.

BACKGROUND The membrane processes are interesting and economical techniques for reuse of municipal and industrial wastewater as well as seawater desalination. However their drawbacks can be resumed in the fouling and biofouling due to the deposition and adsorption phenomenon of the components and the development of biofilm on membrane surface. Several studies have focused on the effect of the incorporation of nanoparticles in polymeric membrane matrix on the biofouling properties. Few relevant patents to the topic have been reviewed and cited. METHODS Polyethersulfone (PES) membranes filled with silver nanoparticles (AgNPs) were prepared by non-solvent induced phase separation (NIPS) process using polyvinylpyrrolidone (PVP) as additive and N-Methyl-2-pyrrolidone (NMP) as solvent. Dope solution compositions, coagulation bath (CB) compositions, time before immersion in CB and casting speed were systematically studied. Membrane structure was characterized by scanning electron microscopy, contact angle, streaming potential measurement and X-ray diffraction (XRD). RESULTS Membrane performance was assessed by pure water permeability, antifouling property, porosity and mechanical property. Silver nanoparticles (AgNPs) were prepared by the chemical reduction of silver nitrate solution with freshly prepared fructose solution, using PVP as capping agent and NaOH as accelerant and settled using acetone. The synthesized AgNPs were firstly characterized by Dynamic light scattering (DLS) technique, UV-visible spectrophotometer and X-ray diffraction spectroscopy (XRD). Then, we have selected a 15% PES mixed with 15% of PVP dope solution to prepare PESAgNPs blended membranes. CONCLUSION All the nanocomposite membranes showed superb antibacterial and anti-biofouling performances, indicating that AgNPs in the PES membranes could be an effective approach to minimize membrane biofouling.

Microwave Reinforced Transesterification of Rubber Seed Oil Using Waste Cement Clinker Catalyst

In this study, the potential of limestone based catalyst on microwave assisted closed heating transesterification of Malaysian rubber seed oil (RSO) which is rich in high Free Fatty Acid (FFA) was investigated. The experimental results showed that the conversion of high FFA oil to biodiesel is very efficient compared to various catalysts. The catalytic activity is not negatively affected by the free fatty acids and can be recycled very easily. Brunauer-Emmett-Teller (BET) analysis was also used to find the surface area of the catalyst at each cycle. The highest conversion achieved was 96.80 with catalyst concentration of 6 wt; methanol to oil molar ratio of 5:1; reaction temperature of 60C and reaction time of 60 minutes. The biodiesel produced is within the limits being prescribed by ASTM D 6751.

A Comprehensive Review on Polymeric Nano-Composite Membranes for Water Treatment

During last few decades, membrane technology has emerged as an efficient technique over conventional methods due to its high removal capacity, ease in operation and cost effectiveness for wastewater treatment and production of clean water. Membrane based separations are commonly based on polymeric membranes because of their higher flexibility, easily pore forming mechanism, low cost and smaller space for installation as compared to inorganic membranes. Commonly employed membrane fabrication phase inversion method has been shortly reviewed in this article. Major limitation of membrane based separations is fouling and polymeric membranes being hydrophobic in nature are more prone to fouling. Fouling is a deposition of various colloidal particles, macromolecules (polysaccharides, proteins), salts etc. on membrane surface and within pores thus impedes membrane performance, reduces flux and results in high cost. Modification of polymeric membranes due to its tailoring ability with nanomaterials such as metal based and carbon based results in polymeric nano-composite membranes with high antifouling characteristics. Nanomaterials impart high selectivity, permeability, hydrophilicity, thermal stability, mechanical strength, and antibacterial properties to polymeric membranes via blending, coating etc. modification methods. Characterization techniques has also discussed in later section for studying morphological properties and performance of polymer nano-composite membranes. Graphical Abstract

Tailoring PES membrane morphology and properties via selected preparation parameters

Abstract Polyethersulfone (PES) is among the most interesting materials for membranes preparation, thanks to its outstanding properties, coupled to compatibility with several additives and the facility to be solubilized in several solvents. In this work, flat sheet membranes were prepared by the non-solvent induced phase separation (NIPS) technique, using PES as polymer and polyvinyl pyrrolidone (PVP, 10 kDa) as additive. Preparation and casting conditions were varied and membranes with tailored morphology and properties were obtained. The main objective was to investigate the relationship between selected preparation conditions and membrane features. This may help to understand how to tailor membrane morphology and properties depending on the desired application.