Murari Prasad

Sequestration of carbon dioxide (CO2) using red mud

Red mud, an aluminium industry hazardous waste, has been reported to be an inexpensive and effective adsorbent. In the present work applicability of red mud for the sequestration of green house gases with reference to carbon dioxide has been studied. Red mud sample was separated into three different size fractions (RM I, RM II, RM III) of varying densities (1.5-2.2 g cm(-3)). Carbonation of each fraction of red mud was carried out separately at room temperature using a stainless steel reaction chamber at a fixed pressure of 3.5 bar. Effects of reaction time (0.5-12 h) and liquid to solid ratio (0.2-0.6) were studied for carbonation of red mud. Different instrumental techniques such as X-ray diffraction, FTIR and scanning electron microscope (SEM) were used to ascertain the different mineral phases before and after carbonation of each fraction of red mud. Characterization studies revealed the presence of boehmite, cancrinite, chantalite, hematite, gibbsite, anatase, rutile and quartz. Calcium bearing mineral phases (cancrinite and chantalite) were found responsible for carbonation of red mud. Maximum carbonation was observed for the fraction RM II having higher concentration of cancrinite. The carbonation capacity is evaluated to be 5.3 g of CO(2)/100 g of RM II.

Schorl: a novel catalyst in mineral-catalyzed Fenton-like system for dyeing wastewater discoloration.

Mineral-catalyzed Fenton-like system has been found to be effective for the discoloration of dyeing wastewater. In our present study, schorl has been successfully developed as a novel heterogeneous catalyst for discoloration of an active commercial dye, Argazol blue (BF-BR), in an aqueous solution. Through a number of batch discoloration experiments under various conditions, it was found that the reactivity of the system increased by, respectively, increasing schorl dosage, temperature, hydrogen peroxide starting concentration and by decreasing the pH. At the condition of pH 2, T=55 degrees C, [BF-BR](0)=200mg/L, [H(2)O(2)](0)=48.5 mmol/L and schorl dosage=10 g/L, 100% of discoloration ratio can be achieved in less than 4 min, and 72% of total organic carbon (TOC) can be removed in less than 200 min. The reaction kinetics analysis shows that the discoloration of BF-BR follows the first-order kinetics. The schorl samples after BF-BR discoloration was tested by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Scanning electron microscope (SEM) and the results rule out the possibility of formation of new solid phases during BF-BR discoloration. The content of Fe ion leaching in the solution was also measured using inductively coupling plasma-atomic emission spectra (ICP-AES). A mechanism proposed herein indicates adsorption and Fenton-like reaction (heterogeneous and homogeneous) are responsible for the discoloration of BF-BR.

Adsorption of cyanide from aqueous solutions at pyrophyllite surface

The adsorption of cyanide from aqueous solutions at pyrophyllite mineral surface has been studied by investigating the effect of initial concentration of adsorbate, amount of adsorbent, pH and temperature of test solutions. The adsorption efficiency is observed to be 99% in dilute solutions but decreases down to 40% with increase in cyanide concentration to 10 ppm. The adsorption is observed to be maximum from neutral solutions and is observed to increase with increase in temperature. The adsorption data have been fitted in Langmuir and Freundlich isotherms and the adsorption has been found to be endothermic in nature in the temperature range 30–60°C.

Kinetic model for sorption of divalent heavy metal ions on low cost minerals

A mathematical model is proposed that could predict the kinetic parameters for adsorption of divalent heavy metal ions (lead, copper and zinc) onto low-cost adsorbents such as pyrophyllite and rock phosphate using experimental data. The experiments were conducted with the initial concentrations of metal ions ranging from 10mg/L to 100mg/L. The mathematical model is based on the application of the Redlich-Peterson isotherm to mass transfer across the film surrounding the adsorbent. The developed non-linear sorption kinetic (NSK) mathematical model was solved using numerical integration by the trapezoidal method in Microsoft Excel along with the SOLVER function to obtain the best simulated values of the Redlich-Peterson constants A, B, r, the order of reaction n, and the film transfer coefficient α. Dissolution followed by precipitation was found to be the most probable mechanism responsible for heavy metal ion uptake by rock phosphate, while for pyrophyllite physical adsorption was governing mechanism at low concentrations (<100mg/L). The values of parameters A, B, r and α lie in the ranges of 0.015-23.2, 0.00003-3.09, 0.072-1, and 0.000057-52.8 [(L/mg)(n−1)/min], respectively, under different experimental conditions.