Kunal Ghosh

Bio: Kunal Ghosh is an academic researcher. The author has contributed to research in topics: Polyelectrolyte. The author has an hindex of 1, co-authored 1 publications receiving 9 citations.

Hymatomelanic acids as polyelectrolytes. I. Viscometric and osmometric studies

Abstract: The polyelectrolyte character of four natural and ten synthetic hymatomelanic acids, synthesized from possible monomers both in the presence and absence of catalysts, was established by means of viscosity measurements. Intrinsic viscosities were evaluated for the purpose of comparison. The number-average molecular weights of some typical natural and synthetic hymatomelanic acids were determined from osmotic pressure measurements. Using the Flory-Fox relationship in an approximate manner, the root-mean-square average end-to-end separations were also evaluated.

The supramolecular structure of humic substances

Abstract: The scientific understanding of the molecular size and shape of humic substances (HS) is critically reviewed. The traditional view that HS are polymers in soil is not substantiated by any direct evidence but is assumed only on the basis of laboratory experiments with model molecules and unwarranted

The supramolecular structure of humic substances: A novel understanding of humus chemistry and implications in soil science

Abstract: The scientific understanding of the molecular structure of humic substances is critically reviewed here. The traditional view that humic substances are polymers in soil is not substantiated by any direct evidence but only assumed on the basis of laboratory experiments with model molecules and unwarranted results by incorrectly applying either analytical procedures or mathematical treatments developed for purified and undisputed biopolymers. A large body of evidence instead shows an alternative understanding of the conformational nature of humic substances which should be regarded as supramolecular associations of self-assembling heterogeneous and relatively small molecules deriving from the degradation and decomposition of dead biological material. A major aspect of the humic supramolecular structure is that it is predominantly stabilized by weak dispersive forces instead of covalent linkages. Hydrophobic (van der Waals, π-π, CH-π) and hydrogen bonds are responsible for the apparent large molecular size of humic substances, the former becoming more important with the increase of pH. Such novel description of humic substances structure better accounts for their essential role in providing and maintaining soil physical and chemical quality and their reactivity towards pesticides and other environmental soil contaminants. This innovative understanding of the nature of humic substances implies a further development of the science and technology for the control of the chemistry and dynamics of natural organic matter in the soil and the environment.

Uv and visible absorption spectroscopic investigations in relation to macromolecular characteristics of humic substances

Abstract: Summary Humic substances were investigated by both UV and visible absorption spectroscopic methods with special emphasis on their macromolecular characteristics. The spectral ranges examined were 200–350 nm and 350–700 nm. Conclusions were drawn on the basis of absorption intensities in optical density (O.D.) vs. wavelength (λ) curves, slopes of log O.D. vs. log λ plots, nature of shoulders in the 250–270 nm region, and E4/E6 ratios. As macromolecular characteristics are expected to be dependent on the medium, studies were carried out at different pH values as well as at different neutral salt concentrations, the two major parameters influencing the soil environment. It was noted that with increasing neutral electrolyte concentrations, the particle size decreased, probably due to the coiling of the macromolecule. On increasing the pH from 6.5 to 9.5, the particle size increased slightly, possibly because of partial association through homolytic bonding. At pH 3.5 (with FA only), the degree of association was greater than that at pH 9.5. However, here association occurred by a different mechanism, that of intermolecular hydrogen bonding. At pH 2.0 (with FA only), association was markedly pronounced because of the very dominant role played by intermolecular hydrogen bonding.

Particle and structure characterization of fulvic acids from agricultural soils

Abstract: Structural studies on fulvic acids (FAs) are of significant importance since FAs are involved in many environmentally important processes, such as adsorption and transportation of nutrients, trace elements, and organic pollutants. Interactions between suspended and dissolved soil components are controlled by a variety of attractive and repulsive interparticle forces influenced partially by FA properties. The aim of this paper is a detailed characterization of FAs derived from agricultural soils varied with physicochemical properties. Forty topsoils (pHKCL = 3.8–7.8, clay content = 0–6%, and TOC = 7.0–187.2 g kg−1) were collected from rural area. Fulvic acids (FAs) were isolated according to the IHSS method. The overall FA solutions were purified by nonionic macroporous acrylic ester resin (DAX-8), and the organic carbon content in FA fraction (FA-OC) was determined by a liquid C–N analyzer. The particle size diameter (PSD) and polydispersity (PDI) were analyzed by a dynamic light scattering technique, while the zeta potential (ZP) was measured using an electrophoretic light scattering method. Spectroscopic properties of FAs, including occurrence and distribution of functional groups, were investigated by near-IR spectroscopy. Agricultural soils differed substantially, with FA-OC content ranging from 0.6 to 8.8 g kg−1 that accounted for 0.5 to 22.6% of TOC. The PSD exhibited wide range of particle size (0.2 to 69.6 nm) and was characterized by different polydispersity (14–183.1%). The ZP described the behavior, and surface charge of FA particles varied from − 1.7 to + 3.3 mV. Low ZP characterized 77% of FAs and indicated the ease of aggregate formation and intermolecular connections. The measured ZP also showed that suspended organic particles of FAs had both positive and negative charges, which was confirmed by the spectroscopic analysis. The presence of negative charges on FA particle surfaces was connected with the occurrence of phenol and carboxyl groups while positive charge with amine. Detailed characterization of FAs from agricultural soils confirms their heterogeneous and complex nature. The results indicate that FAs mainly exist as small molecules that form molecular aggregates or associations in solutions. FA in a solution of a similar ionic strength may be positively or negatively charged due to its chemical structure and aggregate behavior which affects their properties in the soil.

Molecular configuration of compost's humic acid by viscometric studies

Abstract: The macromolecular configuration of humic acid sample obtained from Farm Yard Manure was investigated by viscometric measurements at varying sample concentrations and in presence of a neutral electrolyte. The humic acid molecule behaved like a linear flexible colloid at lower sample concentrations and rigid rod like or sphereo-colloid polyelectrolyte at higher sample concentrations. The polymeric behaviour was alsos shown in the presence of high amount of neutral electrolyte. An analysis of the data for particle weight, volume and axial ratio showed the molecular configuration as rod like.