Krishna Venkatesh

Potential applications of cellulose and chitosan nanoparticles/composites in wastewater treatment: A review.

This work concerns the investigation of potential candidature of cellulose and chitosan-based nano-sized materials for heavy metals and dyes removal. Cellulose and chitosan being the first two abundant biopolymers in nature offer wide opportunities to be utilized for high-end applications such as water purification. The nano-sized cellulose and nano-sized chitosan present superior adsorption behavior compared to their micro-sized counterparts. This area of research which explores the possible usage of nano-biopolymers is relatively new. The present review article outlines the development history of research in the field of cellulose and chitosan, various methods employed for the functionalization of the biopolymers, current stage of research, and mechanisms involved in adsorption of heavy metals and dyes using nanocellulose and nanochitosan. The significance of research using nano-biopolymers and future prospects are also identified.

Plating on acrylonitrile–butadiene–styrene (ABS) plastic: a review

ABS is an engineering plastic that has butadiene part uniformly distributed over the acrylonitrile-styrene matrix. It possesses excellent toughness, good dimensional stability, easy processing ability, chemical resistance, and cheapness. However, it suffers from inherent shortcomings in terms of mechanical strength and vulnerability to environmental conditions. Furthermore, it is non-conducting and easily fretted. Plating on ABS can serve to enhance the strength and structural integrity as well as to improve durability and thermal resistance resulting in metallic properties on the ABS material. ABS is described as the most suitable candidate for plating because it is possible to deposit an adherent metal coating on it by only the use of chemical pretreatment process and without the use of any mechanical abrasion. This article aims to review the history of ABS plastics, properties of ABS, processes and mechanisms of plating, and studies of plating on ABS involving mainly eco-friendly methods of plating by discussing the literature published in recent years. The details of electroplating of ABS carried out in the authors’ laboratory are also presented.

Cerium dioxide and composites for the removal of toxic metal ions

The presence of contaminants in potable water is a cause of worldwide concern. In particular, the presence of metals such as arsenic, lead, cadmium, mercury, chromium can affect human health. There is thus a need for advanced techniques of water decontamination. Adsorbents based on cerium dioxide (CeO2), also named ‘ceria,’ have been used to remove contaminants such as arsenic, fluoride, lead and cadmium. Ceria and composites display high surface area, controlled porosity and morphology, and abundance of functional groups. They have already found usage in many applications including optical, semiconductor and catalysis. Exploiting their attractive features for water treatment would unravel their potential. We review the potential of ceria and its composites for the removal of toxic metal ions from aqueous medium. The article discusses toxic contaminants in water and their impact on human health; the synthesis and adsorptive behavior of ceria-based materials including the role of morphology and surface area on the adsorption capacity, best fit adsorption isotherms, kinetic models, possible mechanisms, regeneration of adsorbents; and future perspectives of using metal oxides such as ceria. The focus of the report is the generation of cost-effective oxides of rare-earth metal, cerium, in their standalone and composite forms for contaminant removal.

The 46 kDa dimeric protein from Variovorax paradoxus shows faster methotrexate degrading activity in its nanoform compare to the native enzyme

Methotrexate degrading enzymes are required to overcome the toxicity of the methotrexate while treating the cancer. The enzyme from Variovorax paradoxus converts the methotrexate in to non toxic products. Methotrexate degrading enzyme from V. paradoxus is a dimeric protein with a molecular mass of 46 kDa and it acts on casein and gelatin. This enzyme is optimally active at pH 7.5 and 40°C and nanoparticles of this enzyme were prepared by desolvation-crosslinking method. Enzyme nanoparticles could degrade methotrexate faster than the native enzyme and they show lower Km compare to the native enzyme. Enzyme nanoparticles show better thermostability and they were stable for much longer time in the serum compare to the native enzyme. Enzyme nanoparticles show better functionality than the native enzyme while clearing the methotrexate added to the serum suggesting their advantage over the native enzyme for the therapeutic and biotechnological applications.

Tribological Studies on Effect of Mixture of Fillers in Polystyrene Matrix Composites

Addition of measured amounts of fillers into a polymer matrix is expected to improve the desired properties of the composites. Also the ease of processability of the matrix and reinforcement is always desired. Use of powder fillers in the polymer matrix at ambient conditions would make the processing much easier. This will help in in situ applications. In the present work, polymer–matrix composites are prepared with polystyrene as the matrix using metal (copper/aluminum/steel) and ceramic (alumina) fillers at ambient conditions. The composites with metallic and ceramic fillers in the ratio of 50:25:25 wt% (polymer:filler 1:filler 2) designated as three-phase composites were investigated for tribological applications. Both copper and aluminum fillers were considered for comparison in terms of their contribution to tribological behavior because of their thermal conductivity, specific heat and density. Polystyrene is filled with metal powder (copper, aluminum or steel) and alumina in equal proportion and subjected to wear and friction tests. The polymer steel–ceramic composite has the least with the other two composites having almost the same values of friction coefficient. The polymer aluminum–ceramic composite has the least wear at all operating conditions. Polymer aluminum–ceramic composite was found to have better wear behavior among the three-phase composites. This may be attributed to the favorable value of density of aluminum, moderate thermal conductivity and excellent specific heat.

Coolant lubricity and coolant-lube compatibility with regard to slideway behavior

Coolants are widely used in industries for metal cutting operations. Though there are varieties of coolants available, the most widely used are water-soluble coolants because of their low cost and better heat dissipation compared to straight cutting oils. In the present investigation, amongst the various causes, which deteriorate the coolant, the role of hardness of water is primarily studied. Accordingly, water from different sources with varying hardness is considered and coolants are prepared from the same. The extent to which hardness can affect the performance of coolants is studied as a function of coolant lubricity in a reciprocating tribometer. Further, the effect of entry of coolants into lubricated machine tool slideways is also assessed by evaluating the mixture of coolant and lubricating oil for its frictional behavior. This is important from assessing the impact of the mixing of coolant and lubricating oil on machine tool slideways with regard to positioning exactness and stick slip behavior of slideways in terms of coolant-lube compatibility.