Robina Farooq

Phytoremediation potential of Arundo donax in arsenic-contaminated synthetic wastewater

The present study reports the potential of Arundo donax for phytoextraction of arsenic from synthetic wastewater. A. donax plants were grown under greenhouse conditions in pots containing a nutrient solution amended with increasing doses of As (0, 50, 100, 300, 600 and 1000 microg L(-1)) for 21 days in a completely randomized design. Shoot and roots dry matter production, growth parameters, arsenic and nutrient tissue concentrations were measured at the end of the experiment. Increasing As concentration in nutrient solution caused an increase in shoot and root biomass without toxicity symptoms in A. donax growing under a range of As concentration from 50 to 600 microg L(-1). Elevated oxidative stress was observed at As supplied level of 1000 microg L(-1). The As doses up to 600 microg L(-1) did not affect the growth of A. donax. It is suggested that A. donax plants may be employed to treat contaminated waters containing arsenic concentrations up to 600 microg L(-1).

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.

Synergistic effects of combining ultrasound with the Fenton process in the degradation of Reactive Blue 19.

The decoloration of reactive dye C.I. Reactive Blue 19 (RB 19) using combined ultrasound with the Fenton process has been investigated. The effect of varying the concentrations of hydrogen peroxide and iron sulfate, initial pH, ultrasonic power, initial dye concentration and dissolved gas on the decoloration and degradation efficiencies was measured. Calibration of the ultrasound systems was performed using calorimetric measurements and oxidative species monitoring using the Fricke dosimeter and degradations were carried out with a 20 kHz probe type transducer at 2, 4, 6 and 8 W cm(-2) of acoustic intensity at 15, 25, 50 and 75 mg L(-1) initial dye concentrations. First order rate kinetics was observed. It was found that while the degradation rate due to ultrasound alone was slow, sonication significantly accelerated the Fenton reaction. While the results were similar to those reported for other dyes, the effects occurred at lower concentrations. The rate and extent of decoloration of RB 19 increased with rising hydrogen peroxide concentration, ultrasonic powers and iron sulfate concentration but decreased with increasing dye concentration. An optimum pH value of pH=3.5 was found. The rate of decoloration was higher when dissolved oxygen was present as compared with nitrogen and argon confirming the solution phase mechanism of the degradation.

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.

Biological treatment of the dye Reactive Blue 19 by cattails and anaerobic bacterial consortia

This study demonstrates the bioremediation potential of anaerobic sludge and cattail (Typha angustifolia) for the treatment of the dye Reactive Blue 19 (RB19). The anaerobic sludge and cattails used in this study were not previously exposed to dyes or other xenobiotics. Different anaerobic sludge concentrations (30%, 50%, and 70%) were used along fixed dye concentrations at pH 8.0 and 25 °C. Subsequently, 50% sludge was selected to treat RB19 at various concentrations. The discoloration of non-hydrolyzed dye was between 70% and 85% using 50% biomass. For the hydrolyzed form of RB19, the range of decoloration was 70%–90%. Dye treatment efficiencies between 50% and 75% were observed for the two forms of the dye when treated with T. angustifolia. Overall, the anaerobic biomass at pH 8.0 showed better potential than cattails to treat RB19. The observation that non-enriched anaerobic sludge can decolorize RB19 is important because it opens up the prospects of developing anaerobic treatment systems, which can easily decolorize dyes in industrial wastewaters and also possesses potential advantages over systems using defined bacterial cultures.

Bio-electrochemical synthesis of commodity chemicals by autotrophic acetogens utilizing CO2 for environmental remediation.

Bio-electrochemical synthesis (BES) is a technique in which electro-autotrophic bacteria such as Clostridium ljungdahlii utilize electric currents as an electron source from the cathode to reduce CO2 to extracellular, multicarbon, exquisite products through autotrophic conversion. The BES of volatile fatty acids and alcohols directly from CO2 is a sustainable alternative for non-renewable, petroleum-based polymer production. This conversion of CO2 implies reduction of greenhouse gas emissions. The synthesis of heptanoic acid, heptanol, hexanoic acid and hexanol, for the first time, by Clostridium ljungdahlii was a remarkable achievement of BES. In our study, these microorganisms were cultivated on the cathode of a bio-electrochemical cell at −400 mV by a DC power supply at 37°C, pH 6.8, and was studied for both batch and continuous systems. Pre-enrichment of bio-cathode enhanced the electroactivity of cells and resulted in maximizing extracellular products in less time. The main aim of the research was to investigate the impact of low-cost substrate CO2, and the longer cathode recovery range was due to bacterial reduction of CO2 to multicarbon chemical commodities with electrons driven from the cathode. Reactor design was simplified for cost-effectiveness and to enhance energy efficiencies. The Columbic recovery of ethanoic acid, ethanol, ethyl butyrate, hexanoic acid, heptanoic acid and hexanol being in excess of 80% proved that BES was a remarkable technology.

Mechanism of Corrosion and Erosion Resistance of Plasma‐ Sprayed Nanostructured Coatings

There has been a dramatic increase in recent years in a demand for tough, wear‐ resistant, abrasion, erosion, and corrosion‐resistant coatings for petroleum, chemical, aerospace industry, and processes encountering harsh environments such as paper and pulp equipment (the ball valve for high‐pressure leaching). Whereas sufficient informa‐ tion on mechanical properties, such as abrasion, wear, and fatigue, has been gathered over the years, work on the resistance of these coatings to erosion and corrosion is seriously lacking. In the work reported, it has been shown that nanostructured TiO2 coatings offer superior physical and mechanical properties compared to conventional TiO2 coatings. Three different types of plasma‐sprayed titanium dioxide coated samples on mild steel substrate were employed for investigation. The feedstocks used were Sulzer Metco nanopowders designated as AE 9340, AE 9342, and AE 9309. Powder 9340 was a precursor. The corrosion resistance of nanostructured TiO2 coating was dictated largely by surface structure and morphology. The distribution and geometry of splat lamellae, contents of unmelted nanoparticles, and magnitude of porosity are the important factors that affect corrosion resistance. TiO2 showed excellent resistance to corrosion in 3% NaCl. The maximum corrosion rate was observed to be 4 mils per year as shown by polarization potential and weight loss studies. The erosion‐corrosion resistance of the plasma‐ sprayed nanostructured titanium dioxide coatings depends largely upon the character‐ istics of feed powder and its reconstitution. Dense, uniform, and evenly dispersed nanostructured constituents provide a high coating integrity, which offers high resistance to erosion‐corrosion. A mechanism of erosion‐corrosion is explained in the chapter with a schematic diagram. The findings show that the nanostructured TiO2 coatings offer superior resistance to corrosion, erosion, and environmental degradation.

Hydrophobicity — A Green Technique for Enhancing Corrosion Resistance of Alloys

The corrosion phenomenon is as old as the age of the planet. The cost of corrosion has risen alarmingly with industrial progress and it is estimated to be around 300 billion dollars or 3 to 4.5% of the GNP of developed nations. Thousands of alloys have been developed to control corrosion, which is a major consideration in the development of new ferrous and non-ferrous alloys. Several corrosion control techniques such as inhibitor treatment, coatings, cathodic protection, alloying additions, and designing for corrosion protection have been developed to combat corrosion. Despite their merits, techniques such as inhibition treatment and coatings are limited by their adverse effect on the environment because of their volatile organic components. Due to an increasing‐ ly alarming carbon footprint, there is a growing global concern to keep the environ‐ ment clean. Hence, a great need exists to replace the current control methods by ecofriendly methods. The potential of the green technology of hydrophobicity has therefore been exploited to control corrosion by fabricating hydrophobic surfaces on alloys and these surfaces have shown highly promising results. This technology offers a novel method to control corrosion of metals, alloys, polymers and composites.

Microbial Fuel Cells and Their Applications for Cost Effective Water Pollution Remediation

Abstract A recent research in the field of microbial fuel cell (MFC) is exploring bio-electrochemical processes to generate electricity. Fundamentals to microbial fuel cell are proper cost effective cell design, electrodes, substrates, proton exchange membranes and bacterial species forming biofilms on electrode. The MFC is considered to be specific for current generation by bacterial metabolism. The current review uncovers the fact that MFC technology is not only for the current generation but is also effective for bio-remediation, bio-sensors and for biosynthesis of valuable organic products. Industrial and domestic wastes are pollutants, toxic for health and environment. Their chemical treatment itself requires expensive chemicals which in turn lead to other composites in the environment. The cost effective and safe technique has been employed for remediation like catalytically active bio-electrodes in MFC. The exoelectrogens are capable of electron transfer by forming conductive biofilms on the solid surfaces of electrodes. The Geobacter, Shewanella and Sporomusa species have the tendency to form nanowires or have C-type cytochromes for electron conduction. The redox capability of these electro active biofilms is not only to reduce the hazardous materials but also to catalyze the electrochemical reactions like corrosion alleviation, biosensor development, bio-remediation and biochemical synthesis. These bio-electrochemical techniques have been proved to be the best for low cost, high catalytic activity, less pollution and no secondary contaminants.