Ravi P. Jaiswal

Bio: Ravi P. Jaiswal is an academic researcher from Indian Institutes of Technology. The author has contributed to research in topics: Adhesion & Wastewater. The author has an hindex of 6, co-authored 26 publications receiving 215 citations. Previous affiliations of Ravi P. Jaiswal include Kamla Nehru Institute of Technology & Purdue University.

Modeling and validation of the van der Waals force during the adhesion of nanoscale objects to rough surfaces: a detailed description.

Abstract: The interactions between nanoparticles and rough surfaces are of great scientific and engineering importance and have numerous applications in surface science and biotechnology. Surface geometry and roughness play crucial roles in observed particle adhesion forces. We previously developed a model and simulation approach to describe adhesion between microscale bodies. This work provides detailed descriptions of the modeling framework, with associated experimental validation, applied to nanoscale systems. The physical systems of interest include nanoscale silicon nitride adhering to different surfaces in both dry and aqueous environments. To perform the modeling work, precise descriptions of the geometry of the particle and the roughness of the particle and substrate were generated. By superimposing the roughness and geometry models for the particle and the substrate, it was possible to precisely describe the spatial configurations of the adhering surfaces. The interacting surfaces were then discretized, and the adhesion force between the two surfaces was calculated by using Hamaker's additive approach, based on van der Waals interactions. In the experimental work, an atomic force microscope (AFM) was used to measure the adhesion force (pull-off force) between nanoscale silicon nitride cantilever tips and a range of substrates in different environments. The measured and predicted force distributions were compared, and good agreement was observed between theory and experiment.

A comprehensive review on the integration of advanced oxidation processes with biodegradation for the treatment of textile wastewater containing azo dyes

Abstract: The threat of dye contamination has achieved an unsurpassed abnormal state lately due to their massive consumption in several enterprises including textile, leather, cosmetic, plastic, and paper industries. This review focuses on the integrations of various advanced oxidation processes (AOPs), such as Fenton, photocatalysis, and ozonation, with biodegradation for the treatment of textile azo dyes. Such integrations have been explored lately by researchers to bring down the processing cost and improve the degree of mineralization of the treated dyeing wastewater. The review refers to the basic mechanisms, the influence of various process parameters, outcomes of recent works, and future research directions. All the three AOPs, independently, demonstrated substantial color reduction of 54–100%. The ozonation process, stand-alone, showed the most efficient decolorization (of 88–100%) consistently in all reviewed research works. In contrast, all three AOPs independently offered varied and inadequate COD reduction in the range of 16–80%. The AOPs, after getting integrated with biodegradation, yielded an additional reduction (of 11–70%) in the COD-levels and (of 16–80%) in the TOC-levels. Further, the integration of AOPs with biodegradation has potential to significantly reduce the treatment costs. The review suggests further research efforts in the direction of sequencing chemical and biological routes such that their synergistic utilization yield complete detoxification of the textile azo dyes economically at large-scale.

Scaling of van der Waals and Electrostatic Adhesion Interactions from the Micro- to the Nano-Scale

Abstract: Work performed to study the scalability of continuum force models to describe particle adhesion from the micro- to the nano-scale is described. This work employed silicon nitride particles with nominal diameters on the micrometer scale and silicon nitride atomic force microscope cantilevers with nanometer-scale radii of curvature to determine adhesion interaction forces to substrates relevant to advanced lithography applications in the semiconductor industry. The force required to dislodge the particles or cantilevers from the substrates was taken to be the adhesion force. For all systems studied, a distribution of adhesion forces was observed resulting from roughness on the particles and/or substrates and geometry variations on the particles. Previously developed adhesion models that included van der Waals (vdW) and electrostatic (ES) interactions, and that also included the geometry and morphology of the interacting surfaces, were used to describe the force distributions. In air, the ES forces were foun...

Theoretical Models for Surface Forces and Adhesion and Their Measurement Using Atomic Force Microscopy

Abstract: The increasing importance of studies on soft matter and their impact on new technologies, including those associated with nanotechnology, has brought intermolecular and surface forces to the forefront of physics and materials science, for these are the prevailing forces in micro and nanosystems. With experimental methods such as the atomic force spectroscopy (AFS), it is now possible to measure these forces accurately, in addition to providing information on local material properties such as elasticity, hardness and adhesion. This review provides the theoretical and experimental background of afs, adhesion forces, intermolecular interactions and surface forces in air, vacuum and in solution.

Diversity of Synthetic Dyes from Textile Industries, Discharge Impacts and Treatment Methods

Abstract: Natural dyes have been used from ancient times for multiple purposes, most importantly in the field of textile dying. The increasing demand and excessive costs of natural dye extraction engendered the discovery of synthetic dyes from petrochemical compounds. Nowadays, they are dominating the textile market, with nearly 8 × 105 tons produced per year due to their wide range of color pigments and consistent coloration. Textile industries consume huge amounts of water in the dyeing processes, making it hard to treat the enormous quantities of this hazardous wastewater. Thus, they have harmful impacts when discharged in non-treated or partially treated forms in the environment (air, soil, plants and water), causing several human diseases. In the present work we focused on synthetic dyes. We started by studying their classification which depended on the nature of the manufactured fiber (cellulose, protein and synthetic fiber dyes). Then, we mentioned the characteristics of synthetic dyes, however, we focused more on their negative impacts on the ecosystem (soil, plants, water and air) and on humans. Lastly, we discussed the applied physical, chemical and biological strategies solely or in combination for textile dye wastewater treatments. Additionally, we described the newly established nanotechnology which achieves complete discharge decontamination.

Surface Roughness Effect on Deposition of Nano- and Micro-Sized Colloids in Saturated Columns at Different Solution Ionic Strengths

Abstract: In this study we conducted experiments with saturated columns packed with sand and glass beads to quantitatively examine surface roughness effect on deposition and release of micro- and nano-sized colloids at different solution ionic strengths. Experimental results showed more colloid retentions in both primary and secondary energy minima in sand than in glass bead columns, especially at high solution ionic strengths (e.g., >0.01 M). This observation cannot be explained by the classic Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, which assumes sphere-smooth surface configuration. We modified the Derjaguin approximation approach and calculated interaction energies, which indicate that the sharp asperities on sand surfaces can facilitate colloid deposition in primary minima by reducing the energy barrier. In addition, the increased attachment in secondary minima in sand columns can be attributed to the presence of the valleys on sand surfaces where colloids associated at secondary minima can be shielded from hydrodynamic shear. Additional theoretical analysis verified that large valleys can locally increase the energy barrier as well as the secondary-minimum depth, and hence, are favorable for colloid deposition in secondary minima. Whereas the reduction effects of surface roughness on energy barrier has been extensively addressed in the literature, our modified DLVO analysis and experimental results demonstrate that the effect of this mechanism is only effective at high ionic strength for large colloids (e.g., >0.01 M for the 1156 nm colloid in this study). We provide experimental evidence and theoretical demonstration that surface roughness also plays an important role in colloid deposition at secondary minima under unfavorable conditions. Our study provides a more complete understanding of the effect of surface roughness on colloid deposition.