Raj Kumar Arya

Removal of Mercury(II) from Aqueous Solution: A Review of Recent Work

Mercury is one of the most toxic heavy metals in existence. It is toxic at one in one billion part quantities. Just like chemical toxicity, heavy metal toxicity has become one of the most dangerous health hazards nowadays. The removal of these heavy toxic metals by conventional methods generate a huge quantity of toxic chemical sludge and are not economical both in terms of operating and capital costs. Extensive research has been done by earlier researchers to minimize the impact of mercury because indirectly it is responsible for affecting our environment such as water, air, and land pollution and often leads to health hazards. Several researchers have developed a new alternative and low cost removal technique at laboratory scales which may have great potential for commercial applications. The purpose of this review article is to provide the summary of various techniques or methods available for removal of mercury(II) from aqueous solutions based on adsorption capacity and removal efficiencies. Some of the adsorbents like zinc cementation and polymer supported hydroxyl ethyl suphonamides are highly efficient adsorbent whose removal efficiencies are up to 99%.

Measurement of Concentration Profiles in Thin Film Binary Polymer-Solvent Coatings Using Confocal Raman Spectroscopy: Free Volume Model Validation

Concentrations of solvent and polymer have been measured using confocal Raman spectroscopy in poly(styrene)-tetrahydrofuran, poly(methyl methacrylate)-tetrahydrofuran, and poly(styrene)-p-xylene systems. Free volume theory parameters have been regressed from the measured concentration data. Model-predicted concentration profiles are in very good agreement with the measured profiles in the case of a highly volatile solvent. For instance, free-volume-model-predicted profiles are in very good agreement in poly(styrene)–tetrahydrofuran system and poly(methyl methacrylate)–tetrahydrofuran system. However, the free volume model is not able to predict entire measured profiles in the case of less-volatile solvent in poly(styrene)–p-xylene system.

Finite element solution of coupled-partial differential and ordinary equations in multicomponent polymeric coatings

Abstract Mass transport equations in multicomponent polymeric coatings are nonlinear coupled partial differential equations. These equations were solved using Galerkins method of finite elements which converts them to ordinary differential equations. Residuals were made orthogonal by using quadratic basis functions. Non-uniform elements were used to capture steep concentration gradient near the top of the coating. Finite element formulation has been solved using ode15s of MATLAB. Results are in very good agreement with the earlier results using different solution techniques.

Sensitivity analysis of free-volume theory parameters in multicomponent polymer-solvent-solvent systems

Abstract Sensitivity analysis of free-volume theory parameters have been done in ternary polymer-solvent-solvent systems. Two ternary polymer-solvent-solvent systems have been studied: poly(styrene)-tetrahydrofuran-p-xylene and poly(methyl methacrylate)-ethylbenzene-tetrahydrofuran systems. Simulation analysis has been done to see the effect of all parameters involved in predicting the self-diffusion coefficient in polymer-solvent systems. Sensitivity analysis showed that the predictions are highly sensitive to ξ13 and ξ23 and, therefore, they need to be predicted with good accuracy and these two are not pure component properties.

Calibration Curves to Measure Concentrations in Multicomponent Polymeric Coatings Using Confocal Raman Spectroscopy

Confocal Raman spectroscopy is used to measure concentration of solvents and polymer in ternary polymer - solvent -solvent coatings. A laser beam is focused through a pinhole arrangement at a location inside a sample. The scattered light is captured by a detector and its spectra are recorded in an attached computer. The spectrum is reported as intensity (in some arbitrary units) versus wave number (cm- 1). Ternary and binary polymer solvent systems should be chosen in such a way that the polymer and the solvents should be distinguished by having characteristic peak at some different wave numbers. The ratio of the intensity of the polymer to that of the solvent is calibrated against known ratio of concentration of the polymer to that of the solvent.

Adsorption removal of malachite green dye from aqueous solution

Abstract In this review, the state of the art on the removal of malachite green dye from aqueous solution using adsorption technique is presented. The objective is to critically analyze different adsorbents available for malachite green dye removal. Hence, the available recent literature in the area is categorized according to the cost, feasibility, and availability of adsorbents. An extensive survey of the adsorbents, derived from various sources such as low cost biological materials, waste material from industry, agricultural waste, polymers, clays, nanomaterials, and magnetic materials, has been carried out. The review studies on different adsorption factors, such as pH, concentration, adsorbent dose, and temperature. The fitting of the adsorption data to various models, isotherms, and kinetic regimes is also reported.

Design of Binary Polymeric Coatings for Minimizing the Residual Solvent, Part I: Experimentation

Several binary polymeric coatings of poly(styrene)–tetrahydrofuran have been dried under quiescent drying conditions. Coatings are made using four different solutions of polymer having 5.01, 9.75, 10.06, and 15.14 wt% poly(styrene) initially. Experiments were performed for several different thicknesses for each polymer solution. Residual solvent remaining was lowest in the thicker coating. Results show that the thicker coating should be applied once rather than layer by layer to minimize the remaining residual solvent. The next layer is applied after complete drying of the previous layer. This practice should continue until the desired thickness is obtained. For instance, coatings of initial thickness 1010 µ m and final thickness 61 µm have residual solvent which is lower than the residual solvent in dried coatings of nearly the same final thicknesses using the layer-by-layer technique.

Drying of Multilayer Polymeric Coatings, Part I: An Experimental Study

Designing of multilayer coatings of poly(styrene)-tetrahydrofuran and poly(methyl methacrylate)-tetrahydrofuran has been studied. Multilayers were prepared by layer-by-layer and simultaneous methods. Several binary polymeric coatings of poly(styrene)-tetrahydrofuran and poly(methyl methacrylate)-tetrahydrofuran systems have been dried under quiescent drying conditions. Gravimetric analyses were performed using an analytical weighing balance. The initial amount of polymer was kept constant in both solution coatings. Coating which is likely to go through the glass transition temperature should be applied on the bottom side in order to minimize the residual solvent. For instance, residual solvent content is high in multilayer coating having poly(methyl methacrylate)-tetrahydrofuran coating on the top and poly(styrene)-tetrahydrofuran coating on the bottom, as compared to multilayer coatings having poly(styrene)-tetrahydrofuran on the top of poly(methyl methacrylate)-tetrahydrofuran coating.

Drying of binary thin film polymeric coatings: an experimental study

Abstract Four binary polymer -solvent systems, poly(styrene)-tetrahydrofuran, poly(styrene) - p-xylene, poly(methyl methacrylate) - ethylbenzene and poly(methyl methacrylate) - tetrahydrofuran, systems have been studied. It has been observed that thicker coatings will retain a higher amount of the residual solvent as compared to thinner coatings. In the case of poly(styrene)-tetrahydrofuran coating residual solvent remaining within the coatings were 9.09% and 4.74% for the coatings of the thicknesses of 967 micron and 559 micron, respectively. Similar trends were also observed in the case of poly(methyl methacrylate)-ethylbenzene, poly(methyl methacrylate)-tetrahydrofuran, and poly(styrene)-p-xylene systems.