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Diffusion in hydrogels has gained much attention owing to diverse applications in many areas. The physical diffusion models have been applied to passive diffusion of ions, drug molecules, and macromolecules in polymers solutions and hydrogels and rarely to periodic precipitations (Liesegang patterns) obtained via reaction–diffusion (RD). Classically, the role of gels in RD systems was assumed to be limited to provide mechanical support to the reaction products and to avoid sedimentation. In the present paper, we have employed the AgNO3 (outer electrolyte)–KCl (inner electrolyte)–agarose (gel matrix) system to identify the role of a hydrogel in the RD system in view of diffusion of outer electrolyte through it. The experiments were performed by varying the agarose volume fractions, keeping the outer and inner electrolyte concentrations constant, and using a 2D classical Liesegang setup. The physical obstruction scaling model (OSM) was applied to arrive at the theoretical diffusion coefficients. The model was validated experimentally by evaluating diffusion coefficients using the time law of the Liesegang patterns. It was observed that, at low volume fractions of gel, the theoretical and the experimental values match within ( ±) 5–20%; however, at high volume fractions, the deviation is > 50%.

In the present study, a method is described for precise determination of spatial characteristics of Liesegang bands formed by employing a classical 1D setup using a web-based free resource (https://www.ginifab.com/feeds/pms/color_picker_from_image.php). The method involves the compartmentalization of the information on each pixel into R (red), G (green), or B (blue) values from the pattern images obtained using a simple digital camera. The values can further be converted to absorbance values by using the system blank. Each trough (or peak) in the graph of RGB values (or absorbance values) corresponds to a band in the pattern. The method is employed to determine the spacing and width of the periodically precipitating AgCl, AgBr, and Co(OH)2 in an agar gel. It is observed that AgCl shows revert banding, and AgBr shows revert banding at the top of the tube and then diverges to regular banding at the bottom of the tube, whereas the Co(OH)2 patterns explicitly show regular banding under given experimental conditions. It is also observed that minute instabilities, such as the formation of secondary bands, can also be visualized by the present method.

Carbon footprints (CFs) are the measure of extent of green house gases (GHGs) emitted from any organization or activity. Reporting of extent of CFs in terms of CO2e from educational campus may be considered as a first step towards sustainable educational practices. The present study employs a bottom up approach where CFs due to consumption of resources from each academic department is evaluated separately and net is obtained by adding contributions from individual departments. This method has the advantage of avoiding the potential overlaps in the calculation. Hence this approach to calculate carbon footprints can lead to their precise CF evaluation. In order to justify above hypothesis, CF evaluation was carried out at Shikshana Prasarak Mandali's Sir Parashurambhau College, Pune for three consecutive years starting from 2015 to 2016. The average carbon footprints over the study period were 3630.57 ± 296.79 tones CO2e per year with per capita emission of 0.81 ± 0.06 tones CO2e. The emission density determined from the average value was found to be 0.0361 ± 0.0029 tCO2e m−2 of the campus. It was observed that emission sources classified as scope-1, scope-2 and scope-3 contribute 28%, 48% and 25% respectively to total emission. Out of all the emission sources identified, apart from human contribution through respiration, electricity (35%), biodegradable and non-biodegradable waste, stationary paper, 7%, use of chemicals in the laboratories (5%), paper for official purpose (12%), LPG (3%) and transport (27%) were main contributors. As this is a multi faculty college, science faculty contributes almost 62%, commerce 9% and arts 11% of the total emission.

A periodically precipitating system wherein interband distance successively decreases is known as revert Liesegang banding. The phenomenon is rare, and the underlying mechanism is implicit. In the ...

The present work focuses on the remediation of Methylene Blue dye (MB) by adsorption on Fuller's earth clay (FE). The optimum batch limits for MB adsorption are; pH 8; equilibration time 3 ​h; initial concentration 100 ​mg ​L−1; agitation speed 300 ​rpm; a dose of adsorbent 2 ​g ​L−1, and temperature 25 ​°C. FE clay was characterized using XRD and FESEM. XRD analysis indicated montmorillonite to be the major component of FE. FESEM images indicated clay surface to be layered with high surface area and porosity thereby making it an excellent material for dye adsorption. Classical Langmuir, Modified Langmuir, Freundlich, and BET adsorption isotherms were studied to investigate the adsorption mechanism of MB on FE. Modified Langmuir isotherm fits well for adsorption of MB on FE with an adsorption capacity of 11587 ​mg ​g−1. Kinetic studies revealed the adsorption process to follow Pseudo Second-order kinetics with the energy of activation 28 ​kJ/mol, indicating the adsorption process to be physisorption. Thermodynamic studies indicated the adsorption process to be spontaneous and endothermic. The Artificial Neural Network (ANN) model was employed in the FE system, and the model confirmed its applicability. According to error analysis, ANN was found to be more appropriate model than pseudo second-order model. Sensitivity calculations from ANN data indicated the pH of adsorption to be the most influential factor in MB adsorption with 29% relative importance. The sorption process may be practically valuable on an industrial scale to remediate MB from water assets at an economical price.

The present work highlights the kinetics of sorption of Methylene blue dye (MB) through Alginate-Fuller's earth (ALFE) composite bead interface using the fractal approach. The ALFE beads were characterized using FESEM, FTIR, and BET surface analysis studies. The specific surface area and pore volume of the ALFE beads as obtained by BET analysis are 11.6412 m2/g, and 3.2953 cm3/g respectively indicating mesoporosity. Montmorillonite was found to be the major component of Fullers earth from XRD analysis. The bead's adsorption efficiency was optimized for different experimental conditions like pH, adsorbent dosage, MB concentration, and contact time. The adsorption data was found to fit well using the Freundlich and modified Langmuir- Freundlich adsorption isotherm model, thereby reflecting the adsorbent's energetically heterogeneous surface. The heterogeneity exponent 'h' was more than zero, thereby proving the fractal approach to be more appropriate for explaining sorption's kinetics. The time-dependant pseudo first order instantaneous rate coefficient kinst,1 when plotted against the contact time showed a gradual decrease, thereby bringing out the presence of three different stages in the sorption process differing in their sites of sorption and also in the amount of MB sorbed. The ALFE beads were reusable, and the simulated kinetic data using the fractal approach could be instrumental in designing a continuous flow reactor in an MB dye treatment plant.

Present study illustrates the significant enhancement in the adsorption capacity of glutaraldehyde cross-linked chitosan (C) films through immobilization of 1,5-diphenyl carbazide (D) towards Cr(VI). TGA studies reveal incorporation of about 11% D within the pores of the film while FESEM analysis further confirm thread like nature containing hydrophobic voids. Contact angle measurements suggest the appropriate balance of hydrophilic/hydrophobic nature of film through successive modifications with glutaraldehyde (G) and D. It is observed that Cr(VI) uptake by films is substantially improved by about 25% at pH 2 that follows pseudo first order kinetics with a rate constant value of 0.085 h − 1 . Adsorption studies suggest that removal of Cr(VI) is a spontaneous process occurring mainly through pore diffusion process with removal capacity of 166 mg g − 1 . XPS analysis of Cr(VI) treated C + G + D film indicate formation of Cr-D complex on the surface of film as well as presence of predominantly adsorbed Cr(III) species. It is interesting to note that there exists strong binding of Cr(III) with D present within the pores of film in a quantitative manner. Thus, it can be argued that incorporation of a selective chelating agent like D has substantial effect on removal efficiency of C + G + D for Cr(VI); an approach possessing potential applications in membrane technology.

The present paper highlights the effect of ionic strength due to addition of potassium chloride (KCl) in a diffusing medium on the periodic precipitation (Liesegang patterns) of CoCl2 + NH4OH system. The patterns are obtained by addition of known amount of KCl in an agar gel medium in a glass tube. In the absence of KCl, the precipitating system exhibits a common trend of increase in spacing between consecutive bands with the movement of outer electrolyte towards the lower boundary of the tube thus maintaining constant value of spacing coefficient. However it was observed that the addition of KCl causes decrease in the value of spacing coefficient. The presence of KCl also results in a marked deviation in the width and the time of formation of the precipitating rings. Periodicity of the precipitation pattern is lost and continuous precipitation is obtained in the presence of excess KCl.

The potential of uncharred biomaterial derived from dry leaves of Ficusbenjamina (Family: Moraceae,local name: Weeping Fig) plant to remove Cr(VI) from aqueous samples was investigated. In the present work, treatment of dilute acids was used for activating the adsorption centres on the biomass instead of cumbersome charring process. The plant material was characterized using FT-IR, FE-SEM and EDX. Various influencing factors such as pH of equilibrating solution, contact time, Cr (VI) concentrations, adsorbent dose and temperature were optimized to obtain maximum sorption efficacy. The interactions among the biomaterial and Cr (VI) in water were studied by fitting the sorption data in four different adsorption isotherms. The data fitting and experimental evidences indicated formation of monolayer of Cr(VI) over the biomass surface. The process followed pseudo-second order kinetics and was thermodynamically spontaneous under laboratory conditions and reached equilibrium in 24 hours. Maximum adsorption capacity of 56.82 mg/g was obtained at the pH 2 when the concentration before adsorption was 200 mg L−1 of Cr(VI) with 24 hours of equilibration time and 2.50 g L−1 of dose of biomaterial at room temperature. The sorption efficiency was found to be better than many charred bio-based materials.

Natural Chitosan (C) and Chitosan blended with Poly vinyl Alcohol (PVA) C + P film was prepared by solution casting method for the sorption of Cu(II) from aqueous solution. The FTIR studies revealed that the amino group of chitosan played key roles in the copper uptake and FE-SEM and EDAX studies confirmed the formation of Cu-amino complex in 1:1 ratio of metal to ligand. The prime objective of present studies is the evaluation of thermodynamic parameters (ΔG0, ΔH0 and ΔS0) via reaction stoichiometry and the corrected Langmuir parameter for sorption of Cu(II) on chitosan (C) and (C + P) films. The surface morphology, stability and Cu(II) adsorption efficiency of the films were investigated. The C + P film showed enhanced chemical and mechanical endurance over the C film. The batch adsorption studies exhibited that the adsorption capacity of both the films was pH dependant and the maximum adsorption obtained was 55.56 mg g−1 for C film and 35.71 mg g−1 for C + P film at pH 5.5. The adsorption process was described by Langmuir adsorption model and was found to follow pseudo first order kinetics. The Gibbs free energies calculated using the formation constant Kn and the corrected dimensionless Langmuir constant KL(C) were in good agreement with each other thereby confirming the formation of pendant complex [Cu-NH2]2+. The C + P film could be reused till 5 desorption cycles using EDTA as the desorbing agent and could recover around 169.16 mg of Cu(II) per g of the material.

Studies on bioaccessibility of elements were carried out by in-vitro gastrointestinal digestion simulation method combined with neutron activation analysis (NAA) using NH4HCO3 as an alternate base to commonly used base of NaHCO3. The effect of two bases namely NaHCO3 and NH4HCO3 on the bioaccessibility of the elements namely Br, Fe, K, La, Na, Rb, Sm and Zn from wheat seeds, fresh wheatgrass and commercial wheatgrass tablet was investigated. The bioaccessible concentrations of the elements were determined by neutron activation analysis (NAA). The bioaccessible concentrations of samples digested using NH4HCO3 were found to be higher by 10–15% for most of the elements than that observed using NaHCO3. In the case of fresh wheatgrass, the differences were as high as 50%. The present study indicated that NH4HCO3 can be used as a base instead of NaHCO3 in in-vitro gastrointestinal digestion simulation method.

Bioaccessibility of some essential elements namely K, Mn, Zn, Fe and Na from wheatgrass, consumed as dietary supplement, was measured by in vitro gastric and gastro-intestinal digestion methods. Neutron activation analysis was used to determine bioaccessible concentration of these elements. Bioaccessibility of these elements in commercial wheatgrass tablets and wheat grains was also determined. From both the methods, it was found that bioaccessibility of the elements studied was the highest from fresh wheatgrass and the lowest for wheat seeds. The range of values determined by gastric digestion for wheatgrass, wheatgrass tablets and wheat seeds were 37-57%, 17-43% and 9-38% respectively. Corresponding bioaccessibility values determined by gastro-intestinal digestion method were 39-60%, 34-55% and 15-23% respectively. These studies suggested that fresh wheatgrass grown in the laboratory is an effective source of minerals.

Samples of shoots and roots of tender wheatgrass/wheat plants collected over a period of 20 days were analysed by instrumental neutron activation analysis. The wheatgrass (wheat: Triticum aestivum L.) samples analysed were grown in three different conditions namely (i) tap water, (ii) nutrient compounds with tap water, and (iii) soil and tap water. A total of 15 elements were determined in these samples. In addition, a commercially available wheatgrass tablet was analysed. Accuracy of the method was evaluated by analysing two biological reference materials, SRM 1573a (Tomato leaves) from NIST and ICHTJ-CTA-vtl-2 (Tobacco leaves) from INCT. The paper discusses the elemental concentration levels, their trends and concentration ratios of elements in shoot-to-root grown in these three conditions of growth. It was observed that the elements such as K, Na, Ca and Mg increased linearly in the shoots with the growth period whereas the concentrations of the elements namely Zn, Mn and Fe remained constant in shoots after 8th day of plant growth for all three conditions of growth. However, it was observed that the shoot to root concentration ratio in all the conditions increased linearly for K, Na, Ca, Mg and Cl and decreased for Zn, Fe, Mn, and Al with growth period.

The antioxidant activity of wheatgrass, which is consumed as a dietary supplement, was estimated at different levels. The methods employed include FRAP (ferric reducing antioxidant power), ABTS (2,2'-azobis-3-ethylbenzthiazoline-6-sulfonic acid) and DPPH (1,1'-diphenyl-2-picrylhydrazyl) assays. Aqueous and ethanol extracts of wheatgrass grown under different conditions over a period of 6, 7, 8, 10 and 15 days were used. Lipid peroxidation and oxygen radical absorbance capacity (ORAC) were determined and utilized to check the potency of a few selected extracts. Different conditions used for growth were (1) tap water, (2) tap water with nutrients, (3) soil and tap water, and (4) soil with nutrients. For comparison, a commercially available wheatgrass tablet was analysed. To explain the reasons behind the observed differences, the total phenolic and flavonoid contents of the extracts were measured. These contents increased with growth under all the conditions. The ethanol extracts were found to have a higher phenolic and flavonoid content than the aqueous extracts. The highest FRAP values occurred on day 15 of growth under condition 4, the values being 0.463 and 0.573 mmol of ascorbic acid and Trolox equivalents/100 g fresh wheatgrass for aqueous and ethanol extracts, respectively. In the aqueous extracts no specific trend was observed with the DPPH assay for the different conditions nor for the growth period. In the case of ethanol extracts, however, it increased with the growth period and the wheatgrass grown in condition 4 was found to be the most effective. These extracts were also found to inhibit significantly ascorbate-Fe2+ induced lipid peroxidation in rat liver mitochondria. The ORAC values of aqueous and ethanol extracts of day 10 with condition 4 were found to be 39.9 and 48.2, respectively, being higher than those reported for many natural extracts or vegetables.

In the present work, a simple and rapid method for determination of iodate is described. Iodometric reaction between iodate, excess iodide, and acid has been used, and the iodine liberated is allowed to react with variamine blue (VB) dye in the presence of sodium acetate to yield a violet-colored species. A calibration curve was obtained in the concentration range of 2 to 30 μg of iodate in a final equilibration volume of 10 mL. The effect of different interfering anions on determination of iodate was also studied. The developed method was applied to iodate determination in various iodized salt samples obtained from local markets in and around Pune city, India. The amount of iodate in various table salt samples was in the range of 10 to 25 ppm.