Muhammad Tahir Amin

A Review of Removal of Pollutants from Water/Wastewater Using Different Types of Nanomaterials

The rapidly increasing population, depleting water resources, and climate change resulting in prolonged droughts and floods have rendered drinking water a competitive resource in many parts of the world. The development of cost-effective and stable materials and methods for providing the fresh water in adequate amounts is the need of the water industry. Traditional water/wastewater treatment technologies remain ineffective for providing adequate safe water due to increasing demand of water coupled with stringent health guidelines and emerging contaminants. Nanotechnology-based multifunctional and highly efficient processes are providing affordable solutions to water/wastewater treatments that do not rely on large infrastructures or centralized systems. The aim of the present study is to review the possible applications of the nanoparticles/fibers for the removal of pollutants from water/wastewater. The paper will briefly overview the availability and practice of different nanomaterials (particles or fibers) for removal of viruses, inorganic solutes, heavy metals, metal ions, complex organic compounds, natural organic matter, nitrate, and other pollutants present in surface water, ground water, and/or industrial water. Finally, recommendations are made based on the current practices of nanotechnology applications in water industry for a stand-alone water purification unit for removing all types of contaminants from wastewater.

Silver disinfection of Pseudomonas aeruginosa and E. coli in rooftop harvested rainwater for potable purposes

Rainwater harvesting being an alternate source in water scarce areas is becoming a common practice. Catchment contact, however, deteriorates the quality of rainwater making it unfit for potable purposes. To improve the quality of harvested rainwater, silver was used as antimicrobial agent in this study. Rainwater samples were taken from underground storage tank of a rooftop rainwater harvesting system installed in one of the buildings at Seoul National University, Seoul, South Korea. The target microorganisms (MOs) were Pseudomonas aeruginosa and Escherichia coli which were measured by using plate count method and standard MPN method, respectively. The efficiency of silver disinfection was evaluated at concentrations, ranging from 0.01 to 0.1 mg/l; the safe limit approved by WHO. The experiments were performed for 168 h with different time intervals to evaluate the parameters including inactivation rate, residual effect of silver and re-growth in both MOs at lower (i.e. 0.01-0.04 mg/l) as well as the higher concentrations of silver (i.e. 0.08-0.1 mg/l). Results showed the re-growth in both MOs was only in the case of lower concentrations of silver. The possible reason of re-growth at these concentrations of silver may be the halting of bacterial cell replication process for some time without permanent damage. The kinetics of this study suggest that higher inactivation and long term residual effect towards both MOs can be achieved with the application of silver at 0.08 mg/l or higher under safe limit.

Antifungal activity of methanol and n-hexane extracts of three Chenopodium species against Macrophomina phaseolina

Antifungal activity of methanol and n-hexane leaf, stem, root and inflorescence extracts (1, 2, 3 and 4% w/v) of three Chenopodium species (family Chenopodiaceae) namely Chenopodium album L., Chenopodium murale L. and Chenopodium ambrosioides L. was investigated against Macrophomina phaseolina (Tassi) G. Goid., a soil-borne fungal plant pathogen that has a broad host range and wide geographical distribution. All the extracts of the three Chenopodium species significantly suppressed the test fungal growth. However, there was marked variation among the various extract treatments. Methanol inflorescence extract of C. album exhibited highest antifungal activity resulting in up to 96% reduction in fungal biomass production. By contrast, methanol leaf extract of the same species exhibited least antifungal activity where 21–44% reduction in fungal biomass was recorded due to various employed extract concentrations. The various methanol extracts of C. murale and C. ambrosioides decreased fungal biomass by 62–90 and 50–84%, respectively. Similarly, various n-hexane extracts of C. album, C. murale and C. ambrosioides reduced fungal biomass by 60–94, 43–90 and 49–86%, respectively.

Solar Disinfection of Pseudomonas aeruginosa in Harvested Rainwater: A Step towards Potability of Rainwater

Efficiency of solar based disinfection of Pseudomonas aeruginosa (P. aeruginosa) in rooftop harvested rainwater was evaluated aiming the potability of rainwater. The rainwater samples were exposed to direct sunlight for about 8–9 hours and the effects of water temperature (°C), sunlight irradiance (W/m2), different rear surfaces of polyethylene terephthalate bottles, variable microbial concentrations, pH and turbidity were observed on P. aeruginosa inactivation at different weathers. In simple solar disinfection (SODIS), the complete inactivation of P. aeruginosa was obtained only under sunny weather conditions (>50°C and >700 W/m2) with absorptive rear surface. Solar collector disinfection (SOCODIS) system, used to improve the efficiency of simple SODIS under mild and weak weather, completely inactivated the P. aeruginosa by enhancing the disinfection efficiency of about 20% only at mild weather. Both SODIS and SOCODIS systems, however, were found inefficient at weak weather. Different initial concentrations of P. aeruginosa and/or Escherichia coli had little effects on the disinfection efficiency except for the SODIS with highest initial concentrations. The inactivation of P. aeruginosa increased by about 10–15% by lowering the initial pH values from 10 to 3. A high initial turbidity, adjusted by adding kaolin, adversely affected the efficiency of both systems and a decrease, about 15–25%; in inactivation of P. aeruginosa was observed. The kinetics of this study was investigated by Geeraerd Model for highlighting the best disinfection system based on reaction rate constant. The unique detailed investigation of P. aeruginosa disinfection with sunlight based disinfection systems under different weather conditions and variable parameters will help researchers to understand and further improve the newly invented SOCODIS system.

Multiferroicity in sol–gel synthesized Sr/Mn co-doped BiFeO3 nanoparticles

A simple and cost effective sol–gel auto-combustion technique was used to synthesize Bi0.9Sr0.1Fe1−xMnxO3 (x = 0, 0.05, 0.10, 0.15 and 0.20) multiferroics. Rietveld’s refined X-ray diffraction patterns validated the synthesis of pure phase bismuth ferrite nanoparticles adopting a rhombohedrally distorted ABO3 type perovskite structure with space group R3c. Morphology of the prepared samples manifested the improved crystallinity with increasing Mn contents in BiFeO3. Uniformly distributed multi-shaped grains having varying sizes were formed after combustion which would affect the microstructural related properties of the parent compound. Energy dispersive X-ray spectroscopy confirmed the presence of the relevant elements in the prepared compositions according to their stoichiometric ratio. Enhanced saturation magnetization was observed with increasing doping concentration in the parent compound. Improved polarization versus electric field loops were observed in Mn and Sr co-doped BiFeO3 nanoparticles. All the properties in the present research work have been explained on the basis of dopants and their concentrations, phase purity, microstructure and grain sizes.

The effect of reaction atmosphere and growth duration on the size and morphology of boron nitride nanotubes

The effect of different reaction atmospheres is analyzed on the size and morphology of boron nitride nanotubes within a single and continuous growth duration of 180 min at 1200 °C. Field emission scanning electron microscopy micrographs show smaller and larger diameter boron nitride nanotubes in the range of 70–700 nm, with straight and curve parts. Some of the larger diameter boron nitride nanotubes have pipe-like morphologies at their top with the diameter in the range of 270–380 nm. High resolution transmission electron microscopy shows the tubular structure of the synthesized nanotubes with a non-uniform diameter. X-ray photoelectron spectroscopy shows B1s and N1s peaks at 190.3 eV and 398 eV for hexagonal boron nitride nature of the synthesized nanotubes. The Raman spectrum reports a higher intensity peak at 1370 (cm−1) that corresponds to E2g mode of vibration in hexagonal boron nitride.

Enhancing co-metabolic degradation of trichloroethylene with toluene using Burkholderia vietnamiensis G4 encapsulated in polyethylene glycol polymer

The biodegradation potential of Burkholderia vietnamiensis G4 (B. vietnamiensis G4) was evaluated under encapsulation in comparison with direct exposure to trichloroethylene (TCE) (0.1, 0.5, 1 and 5 mg/L) and toluene (10 and 50 mg/L), maintaining aerobic conditions. B. vietnamiensis G4 was encapsulated in polyethylene glycol (PEG) polymer. Under suspended conditions, the degradation rate decreased as the initial TCE concentration increased, even with a higher amount of substrate available. However, the encapsulated systems were less suppressed, presumably by mitigated toxicity, and completely removed TCE with 50 mg/L of toluene. The transformation yield (Ty) was as high as 0.427 mg-TCE/mg-toluene for the encapsulated cultures and 0.1007 mg-TCE/mg-toluene for the suspended cultures. The Ty value for the encapsulated cultures was one to two orders higher than what has been reported in the literature. The higher Ty values in the encapsulated cultures compared with those from suspended cultures showed that the PEG encapsulation provided more a favourable environment for efficient substrate use.

Synergistic effect of nano-sized mackinawite with cyano-cobalamin in cement slurries for reductive dechlorination of tetrachloroethylene

Experiments were conducted to investigate the reductive dechlorination of tetrachloroethylene (PCE) by nano-Mackinawite (nFeS) with cyano-cobalamin (Cbl(III)) in cement slurries. Almost complete degradation of PCE by nFeS-Cbl(III) was observed in cement slurries in 5 h and its degradation kinetics (k(obs-PCE)=0.57 h(-1)) was 6-times faster than that of nFeS-Cbl(III) without the cement slurries. PCE was finally transformed to non-chlorinated organic compounds such as ethylene, acetylene, and C3-C4 hydrocarbons by nFeS-Cbl(III) in cement slurries. X-ray photoelectron spectroscopy and PCE degradation by cement components (SiO2, Al2O3, and CaO) revealed that both the reduced Co species in Cbl(III) and the presence of Ca in cement played an important role for the enhanced reductive dechlorination of PCE. The increase in the concentration of Cbl(III) (0.005-0.1 mM), cement ratio (0.05-0.2), and suspension pH (11.5-13.5) accelerated the PCE degradation kinetics by providing more favorable environments for the production of reactive Ca species and reduction of Co species. We also observed that the degradation efficiency of PCE by nFeS-Cbl(III)-cement lasted even at high concentration of PCE. The experimental results obtained from this study could provide fundamental knowledge of redox interactions among nFeS, Cbl(III), and cement, which could significantly enhance reductive dechlorination of chlorinated organics in contaminated natural and engineered environments.

Enhanced ferromagnetic characteristics in Mn-doped ZnO: A promising diluted magnetic semiconductor

Zn1−xMnxO (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.1) nanocrystalline diluted magnetic semiconductors (DMSs) were synthesized using sol–gel-based auto-combustion technique. X-ray diffraction (XRD) analysis of all the synthesized samples indicated pure wurtzite hexagonal structure without any secondary phase with perfect solubility of Mn contents in ZnO matrix. The increase in Mn concentration reduced the average crystallite size as evaluated by the Scherrer’s formula. Morphological analysis performed using a field emission scanning electron microscope (FESEM) indicated nearly an ordered surface morphology with some porosity and few cracks. Energy dispersive X-ray (EDX) spectroscopy confirmed the stoichiometric contents of Zn, Mn and O in each sample. Micrographs of all the samples exhibited a decrease in grain size with increase of Mn contents. Magnetic measurements performed using vibrating sample magnetometer (VSM) confirmed room temperature ferromagnetism exhibiting an increase in saturation magnetization and coercivity with increasing Mn contents in all the prepared samples.

Effect of the irrigation frequency and quality on yield, growth and water productivity of maize crops

A research study was conducted to examine the crop responses of maize under two irrigation systems, i.e. raised bed and high-efficiency irrigation system (HEIS; drip irrigation) systems, with three irrigation frequencies and three levels of irrigation water quality. The trial was carried out in a completely randomised design mode with triple replication of each treatment. The raised bed irrigation system demonstrated better performance in terms of crop parameters: plant height, biological yield and grain yield for the raised bed system were recorded as 1, 5 and 21%, respectively, higher than the drip irrigation system. Field measurements for the HEIS showed that the biological yield, grain yield and harvest index were quadratically correlated with the frequency of irrigation. Better results were obtained for plots irrigated every 2 or 6 days than for those irrigated every 4 days. Good-quality water raised plant biological yield by 12% and grain yield by 14.85%. The irrigation frequency had a clear-cut eff...