Farrukh Shehzad

Impact of nanoparticles on human and environment: review of toxicity factors, exposures, control strategies, and future prospects

Nanotechnology has revolutionized the world through introduction of a unique class of materials and consumer products in many arenas. It has led to production of innovative materials and devices. Despite of their unique advantages and applications in domestic and industrial sectors, use of materials with dimensions in nanometers has raised the issue of safety for workers, consumers, and human environment. Because of their small size and other unique characteristics, nanoparticles have ability to harm human and wildlife by interacting through various mechanisms. We have reviewed the characteristics of nanoparticles which form the basis of their toxicity. This paper also reviews possible routes of exposure of nanoparticles to human body. Dermal contact, inhalation, and ingestion have been discussed in detail. As very limited data is available for long-term human exposures, there is a pressing need to develop the methods which can determine short and long-term effects of nanoparticles on human and environment. We also discuss in brief the strategies which can help to control human exposures to toxic nanoparticles. We have outlined the current status of toxicological studies dealing with nanoparticles, accomplishments, weaknesses, and future challenges.

Synthesis, characterization and crystallization kinetics of nanocomposites prepared by in situ polymerization of ethylene and graphene

High-density polyethylene (HDPE)/graphene nanocomposites were synthesized by in situ polymerization. Zriconocene was used as a catalyst and methylaluminoxane as a co-catalyst. The effect of graphene on the activity of the catalyst and on chain microstructure, crystallization kinetics, mechanical and thermal characteristics of HDPE was investigated. Both the thermal and mechanical properties of HDPE were enhanced. The catalyst showed a slight reduction in the activity. The molecular weight of the polymer was analyzed by gel permeation chromatography, and a significant increase in weight-average molecular weight (MW) of HDPE was observed in the presence of graphene. Isothermal crystallization kinetics was studied by differential scanning calorimetry. The crystallization rate was increased with the addition of graphene. Microcalorimetric analysis indicated a major decrease in the peak decomposition temperature as well as the total heat released for the HDPE/graphene nanocomposites.

Polymeric Surfactants and Emerging Alternatives used in the Demulsification of Produced Water: A Review

ABSTRACT Stable emulsions are frequently encountered in oil production and cause a series of environmental and operational issues. Chemical demulsification is widely used for the separation of oil from water or removal of water from oil. The chemicals used in the demulsification process have a strong affinity to the oil-water interface. This review presents the various types of chemical demulsifiers used for the demulsification of water-in-oil and oil-in-water emulsions. The review covers the relevant properties of polymeric surfactants such as polyether, dendrimers, and natural biodegradable polymeric surfactants. In addition, emerging alternatives like nanoparticles-based demulsifiers and ionic liquids are also reviewed. The factors affecting the demulsification efficiency of these demulsifiers and structure-property relationships are discussed. Copolymers with high hydrophilic content and molecular weight are more efficient demulsifiers. Similarly, the position isomerism (same carbon skeleton and functional groups but a different location of functional groups) strongly affects the HLB and demulsification performance. Generally, dendrimers show better performance compared to linear polymeric surfactants due to their relatively higher interfacial activity, better penetrability, and a larger number of reactive terminal groups. Techniques used to evaluate the performance of demulsifiers are also covered. The review also highlights the current developments and future prospects of chemical demulsifiers.

Influence of graphene on the non-isothermal crystallization kinetics of poly(vinyl alcohol)/starch composite

Non-isothermal crystallization behavior of poly(vinyl alcohol)/starch and poly(vinyl alcohol)/starch/graphene nanocomposites was studied using differential scanning calorimetry (DSC). Ozawa and Mo models were used to analyze the non-isothermal kinetics. The differential Friedman method was used to evaluate the effective activation energy (EA) of the nanocomposites. The data fits the Mo Model well in the investigated temperature range. Graphene nucleates the crystallization of the composites by increasing the crystallization onset temperature along with the lowering of EA. However, significant changes in the crystallization half-time were not observed, suggesting that the effect of graphene is more prominent at the nucleation stage.