Saleem Farooq Shaukat

Enhanced decomposition of reactive blue 19 dye in ultrasound assisted electrochemical reactor

Textile industry effluents contain reactive dyes that may harm our receiving waters. A typical reactive blue (RB) 19 dye is frequently detected in significant concentrations in textile industry effluents. Such dyes have generally shown resistance to decomposition and tend to persist in the environment for long periods and multiply the impacts to water and environment. Therefore, the present investigation focused on high-rate decomposition of a typical reactive dye RB 19 under various ultrasound and electrochemical process conditions. The decomposition of un-hydrolyzed and hydrolyzed forms of reactive blue (RB) 19 dye by ultrasound assisted electrochemical process was investigated using various parameters including dye concentration, pH, ultrasonic frequency and reaction time. Reaction kinetics, organic carbon and mechanism for dye decomposition were determined using UV-Visible spectrophotometry, TOC (total organic carbon) analysis and gas chromatography-mass spectrometry (GC-MS). Almost complete 90% color removal and a maximum of 56% TOC removal for 50 mg L(-1) dye concentration of un-hydrolyzed RB 19 dye was achieved at an ultrasonic frequency of 80 kHz, pH of 8 after 120 min. GC-MS analysis showed that a sonoelectrochemical treatment of un-hydrolyzed RB 19 dye for 30 min resulted in the formation of products e.g. acetic acid, benzoic acid etc. with the complete removal of dye. For hydrolyzed dye, a treatment of 10 min was enough and the results were comparable with 30 min treatment of un-hydrolyzed dye. Kinetics of ultrasound assisted electrolysis showed that the dye decomposition followed 1st order. The ultrasound assisted electrolysis for dye decomposition and hence decolorization proved to be more effective and the total energy consumption reduced to half as compared with simple electrolysis/sonochemical decomposition. Therefore, ultrasound assisted electrolysis was found to be more effective technique for dye decomposition of an otherwise environmentally persistent reactive dye.

Thermal-pressure-mediated hydrolysis of Reactive Blue 19 dye

The thermal-pressure-mediated hydrolysis rates and the degradation kinetics of environmentally persistent Reactive Blue (RB) 19 dye were studied. The dye decomposition was studied at 40-120 degrees C, pH 2-10, and atmospheric pressure range of 1-2 atm. The intermediates and end products formed during the degradation were identified using gas chromatography/mass spectrometry and a possible degradation pathway of RB 19 was proposed. The stability of the dye in aqueous solution was influenced by changes in pH. At pH 4, half-life was 2247.5 min at 40 degrees C and it reduced to 339.4 min when the temperature was increased to 120 degrees C. Acidic conditions were more conducive to enhance hydrolysis rate than basic ones as the decomposition was optimum at pH 4. The kinetic studies indicated that the rate of hydrolysis apparently followed first order reaction. A linear relationship was observed between hydrolysis rate of RB 19 dye and increasing temperatures and pressures. Overall, 23% dye decomposition occurred in 120 minutes at pH 4, 120 degrees C and pressure of 2 atm. Along with thermal-pressure, a combination of techniques like physico-chemical, biological, enzymatic etc. may be more suitable choice for the effective treatment of RB19 dye.

Effect of ultrasound on the removal of copper from the model solutions for copper electrolysis process

A novel combination of an ultrasonic field with electrolysis for the removal of copper is studied. In the ultrasonic field, cavitation acts as jets and agitates the solution and breaks the barrier layer between the cathode surface and the bulk of the solution, thus increases the metal deposition on the cathode surface. The results show that an ultrasonic field is successful for the removal of low copper concentrations in solution.

The energy crisis in Pakistan: A possible solution via biomass-based waste

Developing countries like Pakistan need a continuous supply of clean and cheap energy. It is a very common fear in todays world that the fossil fuels will be depleted soon and the cost of energy is increasing day-by-day. Renewable energy sources and technologies have the potential to provide solutions to long-standing energy problems faced by developing countries. Currently, Pakistan is experiencing a critical energy crisis and renewable energy resources can be the best alternatives for quickly terminating the need for fossil fuels. The renewable energy sources such as solar energy, wind energy, and biomass energy combined with fuel cell technology can be used to overcome the energy shortage in Pakistan. Biomass is a promising renewable energy source and is gaining more interest because it produces a similar type of fuel like crude oil and natural gas. Energy from biomass only depends upon the availability of raw materials; therefore, biomass can play an important role to fulfill the energy requirements ...

Fault-tolerance and noise modelling in nanoscale circuit design

Fault-tolerance in integrated circuit design has become an alarming issue for circuit designers and semiconductor industries wishing to downscale transistor dimensions to their utmost. The motivation to conduct research on fault-tolerant design is backed by the observation that the noise which was ineffective in the large-dimension circuits is expected to cause a significant downgraded performance in low-scaled transistor operation of future CMOS technology models. This paper is destined to give an overview of all the major fault-tolerance techniques and noise models proposed so far. Summing and analysing all this work, we have divided the literature into three categories and discussed their applicability in terms of proposing circuit design modifications, finding output error probability or methods proposed to achieve highly accurate simulation results.

Improved light-harvesting and thermal management for efficient solar-driven water evaporation using 3D photothermal cones

Solar-driven evaporation based on photothermal membrane has been proved to be promising in the field of fresh water generation, and it is considered as an emerging strategy both in laboratory and in industrial scales. However, further research efforts have to be made on light harvesting and thermal management to improve water evaporation. In this study, an extensive research was carried out to develop a bio-inspired 3D photothermal cone for high-efficiency solar-driven evaporation with minimum light reflection and heat loss to bulk water. The artificial photothermal cone with a polypyrrole (PPy) coating layer was facilely fabricated via chemical vapor deposition polymerization (CVDP). The present 3D cone with a rationally designed conical structure exhibited satisfactory absorbance around 99.2% in the entire solar spectrum, which is comparable with the performances of super-black materials. Additionally, the heat loss has been minimized by elevating the photothermal cone to narrow the contact area between water and the PPy-based cone with good wettability, thus achieving a highly efficient interface heating. The solar conversion efficiency up to 93.8% for evaporation was achieved for the photothermal cone under one sun illumination, which is about 1.7 times as high as the result obtained for a plane film. Based on our results, controlling the 3D morphology can be considered as an important strategy for designing a novel high-efficiency photothermal membrane and also, it provides new opportunities in practical application.

Magnetic nanoparticles (Fe3O4 & Co3O4) and their applications in urea biosensing

Nanobiotechnology has opened a new and exciting opportunities for exploring urea biosensor based on magnetic nanoparticles (NPs) mainly Fe3O4 and Co3O4. These NPs have been extensively exploited to develop biosensors with stability, selectivity, reproducibility and fast response time. This review gives an overview of the development of urea biosensor based on Fe3O4 and Co3O4 for in vitro diagnostic applications along with significant improvements over the last few decades. Additionally, effort has been made to elaborate properties of magnetic nanoparticles (MNPs) in biosensing aspects. It also gives details of recent developments in hybrid nanobiocomposite based urea biosensor.

Low Temperature Synthesis and Properties of BiFeO3

Extensive efforts have been made to synthesize single phase and stoichiometric BiFeO3. Some modified techniques have been tried in synthesizing BiFeO3 as compared with the conventionally used co-precipitation method. Thermogravimetric Analysis/Differential Scanning Calorimetry and x-ray diffraction experiments were used exclusively to explore the effects of heat treatment temperature and time on crystallographic behavior of the prepared BiFeO3 powder. Field emission scanning electron microscopy was used to explore the microstructure of the synthesized BiFeO3. The appearance of different magnetic phases in 57Fe Mössbauer spectra and field dependent magnetization was confirmed on the basis of particle size distribution. In this research, an easy, low cost and high-yield method for the low temperature single phase and stoichiometric synthesis of BiFeO3 has been suggested.

All-optical clock recovery for OCDMA systems with optical time gating

Implementing time gating in ultra-high speed OCDMA networks over long distance transmissions will require precise synchronization in order to suppress the influence of timing jitter on the OCDMA receiver. To implement optical gating, an optical clock is needed to control a switching window i.e., “a time gate” to pass the desired autocorrelation peak while blocking the MAI noise. We demonstrate that the use of a network global clock distribution is not necessary if the receiver synchronization is done via optical clock recovery. In our experimental demonstration a wider eye opening with power budget improvement of ~7.5 dB was achieved when using all-optical clock recovery compare to clock distribution.

Optoelectric Characteristics of Porous Silicon Using a Conducting Polymer

The simple porous silicon-based devices producing stable electroluminescence (EL) by the deposition of a poly-4-dicyanomethylene-4H-cyclopenta dithiophene monolayer (PCDM) into the nanostructure is reported. The structure of these devices is Au/PCDM/porous silicon/Si/Al. The EL emission is bright, visible by the naked eye under normal daylight and broad in wavelength covering the whole visible range with a peak at 620 nm. The emission area of the devices is 1 cm2 . The EL starting voltage is in the range of 14-30 V and the current is around 300 mA. The time stability is good for all the devices tested. After exposure to the air for more than three months, the devices show nearly the same emission intensity without increase of external power supplied. The I-V curves are fitted to a Schottky barrier model with a barrier height of 0.8 eV. The orange photoluminescence band from the porous silicon is due to recombination in the silicon quantum structures both before and after coating with PCDM