Recycling marble wastes and Jarosite wastes into sustainable hybrid composite materials and validation through Response Surface Methodology

During marble processing such as cutting, polishing and grinding, a considerable amount of fine residues refereed as marble processing rejects (MPRs) are produced and have become a serious environmental issue. So the current study deals with the conversion of MPRs into hybrid ceramic composite bricks (CCB) with Jarosite waste in a clay matrix system. Mix design and optimization of CCB was performed to illustrate the potentials of MPRs and Jarosite wastes as low-cost high-value composites materials. Response Surface Methodology (RSM) model was also used in this work for simulation and to optimize the process for improving CCB quality employing classic mixture approach. Detoxification through mineralogical changes was achieved during firing composite bricks at 960 °C ± 2 °C and was confirmed using the XRD analysis. Compressive strength of CCB using 15% MPRs with 1:1 Jarosite waste - clay matrix ratio met the standard quality (>35 kg/cm2) for its use in construction purpose. It is evident from the RSM model results and statistical analysis for the response compressive strength, shrinkage, water absorption capacity, density and leachate concentration of Cd as well as Pb in the CCB is in laudable agreement with actual experimental performance

Effect of surface resistance arising due to surfactant on gas absorption accompanied by a chemical reaction in a foam-bed-reactor

On the basis of an idealized foam bed, a model to predict conversion in a foam-bed-reactor containing surfactant has been developed. The model takes into account the effect of surface resistance, arising due to the presence of a surface active agent, on gas absorption accompanied by a chemical reaction in a foam matrix. To verify the theory, experiments have been carried out in a semi-batch foam-bed-reactor for the absorption of air-carbon dioxide mixture in a foam of sodium hydroxide solution containing finite; concentrations of different surfactants. The surface resistance offered by the molecules of surfactant at the gas-liquid interface reduces the mass transfer rates significantly. The proposed model predicts fairly well the experimentally found depletion values of sodium hydroxide

QSAR models to predict effect of ionic strength on sorption of chlorinated benzenes and phenols at sediment–water interface

It is hypothesised that the experimental sorption coefficient normalised to the organic carbon fraction of sediment (Kocexp) for non-ionic, hydrophobic, organic pollutant depends upon the molecular properties as well as background ionic strength of the aquatic system. The utility of this concept has been demonstrated by incorporating ionic strength as a parameter in the three quantitative structure activity relationships (QSARs) namely octanol-water partitioning coefficient model (Kow model), the linear solvation energy model (LSE model), and molecular connectivity indices theory (MCI model). Four chlorinated benzenes and two chlorinated phenols were employed in the present study. Sorption experiments using sediment from the Patalganga River were conducted in laboratory (bottle point method) at different ionic strengths (viz. 0.01, 0.05, and 0.10 M). The Koccal values predicted using Kow model incorporating ionic strength compare reasonably well with the Kocexp values (r2=0.60 and standard error of estimator i.e. SEE=0.35). The LSE model incorporating ionic strength too, was found to be equally good (r2=0.67, SEE=0.33). An attempt has also been made to validate the QSARs developed in the present study utilising the sorption parameters experimentally measured by Dewulf et al. (1996) (Water Res. 30, 3130–3138) for sorption of toluene, ethylbenzenes, and xylenes onto the sediments from Belgian Continental Shelf and North Sea, as well as Mader et al. (1997) (Environ. Sci. Technol. 27, 1524–1531) for sorption of di-, tri-, tetra chlorobenzenes on pure mineral oxides namely Al2O3 and Fe2O3.© Elsevie

Hazardous jarosite use in developing non-hazardous product for engineering application

Jarosite released from zinc metal extraction process is hazardous in nature and its world wide disposal has become a major environmental concern. In this study, an attempt has been made to immobilise and recycle the jarosite released from Hindustan Zinc Limited, India, using CCRs, so called fly ash, and clay soil. Results revealed that the particle size of jarosite was finer than that of CCRs and had higher porosity and water holding capacity due to fine textured materials resulting in high surface area (10,496.18 ± 30.90 cm2/g). Jarosite contain higher concentration of toxic elements (lead, zinc, sulphur, cadmium, chromium and copper) than that of CCRs. Concentrations of radionuclides such as 226Ra, 40K and 228Ac in jarosite found less than in CCRs are similar to that of soil. Statistically designed experiments on solidified/stabilised (s/s) sintered jarosite–CCRs products confirmed that the compressive strength of jarosite bricks reached as high as 140 kg/cm2 with 14.5% water absorption capacity at the combination of 3:1 ratio of jarosite and clay, respectively, but, concentrations of all the toxic elements recommended by United States Environmental Protection Agency (USEPA)–Toxicity Leachate Characteristics Procedure (TCLP) standard are not within the permissible limits. However, it is confirmed that the toxic elements leaching potentials of s/s-sintered products developed using 2:1 jarosite clay ratio with 15% CCRs comply with the USEPA–TCLP limits and also meet the quality for engineering applications.© Elsevie

Solid wastes generation in India and their recycling potential in building materials.

Presently in India, about 960 million tonnes of solid waste is being generated annually as by-products during industrial, mining, municipal, agricultural and other processes. Of this �350 million tonnes are organic wastes from agricultural sources; �290 million tonnes are inorganic waste of industrial and mining sectors and �4.5 million tonnes are hazardous in nature. Advances in solid waste management resulted in alternative construction materials as a substitute to traditional materials like bricks, blocks, tiles, aggregates, ceramics, cement, lime, soil, timber and paint. To safeguard the environment, efforts are being made for recycling different wastes and utilise them in value added applications. In this paper, present status on generation and utilization of both non-hazardous and hazardous solid wastes in India, their recycling potentials and environmental implication are reported and discussed in details

Coal combustion residues—environmental implications and recycling potentials

To meet the electric power requirement, the world population is greatly dependent on fossil fuel. Presently in India, about 75% of the total electrical energy (i.e.~ 100,000 MW) is generated from fossil fuel and about 105 million tons of coal combustion residues (CCRs) as solid waste/by-product is being released annually during combustion of pulverised bituminous, sub bituminous, and lignite coal. Indian coal typically has ash content of 30–60%, which results in low calorific value however low in sulphur, radioactive elements and heavy metals content. Mostly, the CCRs is being disposed to the ash pond as thin slurry, and more than 65,000 acres of land is occupied in India for storage of this huge quantity of ash which leads ecological and environmental problems. Presently about 27% of the total CCRs produced in India is being recycled and used in various applications. The major utilisation is in cement, concrete, bricks, wood substitute products, soil stabilisation, road base/embankment, and consolidation of ground, land reclamation and for agriculture. In this paper, an attempt has been made to assess the global generation of CCRs, present utilisation and acceptability in Indian context, implications and future potentials to achieve environmental sound management.© Elsevie

Effect of surface resistance arising due to surfactant on gas absorption accompanied by a chemical reaction in a foam-bed-reactor

On the basis of an idealized foam bed, a model to predict conversion in a foam-bed-reactor contg. surfactant was developed. The model takes into account the effect of surface resistance, arising due to the presence of a surfactant on gas absorption with chem. reaction in a foam matrix. To verify the theory, expts. were carried out in a semibatch foam-bed-reactor for the absorption of air-{CO_2} mixt. in a foam of NaOH soln. contg. finite concns. of different surfactants. The surface resistance offered by the mols. of surfactant at the gas-liq. interface reduces the mass-transfer rates significantly. The proposed model predicts fairly well the exptl. detd. depletion values of NaOH

Jarosite characteristics and its utilisation potentials

During metallic zinc extraction from zinc sulphide or sulphide ore, huge quantity of jarosite is being released universally as solid residues. The jarosite mainly contains iron, sulphur, zinc, calcium, lead, cadmium and aluminium. Jarosite released from such industrial process is complex and its quality and quantity make the task more complex for safe disposal. Apart from water contamination, jarosite already accumulated and its increasing annual production is a major source of pollution for surrounding environment including soil, vegetation and aquatic life and hence its disposal leads to major concern because of the stringent environmental protection regulations. An attempt was made to evaluate the characteristics of Indian jarosite with an objectives to understand its potentials for recycling and utilising as raw materials for developing value added products. Sand and Coal Combustion Residues (CCRs) was used as an admixture to attain good workability and detoxify the toxic substance in the jarosite. Result revealed that jarosite is silty clay loam in texture having 63.48% silt sized and 32.35% clay sized particles. The particle size of jarosite (D90 = 16.21 ± 0.20 μm) is finer than the CCRs (D90 = 19.72 ± 0.18 μm). The jarosite is nonuniform in structure and shape as compared to the CCRs having spherical, hollow shaped and some of them are cenosphere in nature. The major mineral phase of jarosite is Potassium Iron Sulphate Hydroxide {KFe3(SO4)2(OH)6}and Iron Sulphate Hydrate {2Fe2O3SO3·5H2O}. In CCRs the dominant phases are quartz {SiO2}, mullite {3Al2O3·2SiO2} and hematite {Fe2O3}. The high electrical conductivity of jarosite (13.26 ± 0.437 dS/m) indicates that the presence of cations and anions are predominant over CCRs (0.498 ± 0.007 dS/m). The major portion of jarosite consists of iron (23.66 ± 0.18%), sulphur (12.23 ± 0.2%) and zinc (8.243 ± 0.075%). But CCRs main constituents are silicon ( 27.41 ± 0.74%), aluminium (15.167 ± 0.376%) and iron (4.447 ± 0.69%). The other constituents such as calcium, aluminium, silicon, lead, and manganese are also present in the range of 0.5 to 5%. Heavy metals such as copper, chromium, and cadmium are found higher in jarosite as compared to the CCRs. The statistically designed experimental trials revealed that the density, water absorption capacity and compressive strength of fired jarosite bricks are 1.51 gm/cm3, 17.46% and 43.4 kg/cm2 respectively with jarosite sand mixture in the ratio of 3 : 1 indicating the potentials in developing building materials.© Elsevie

Solid wastes generation in India and their recycling potential in building materials

Presently in India, about 960 million tonnes of solid waste is being generated annually as by-products during industrial, mining, municipal, agricultural and other processes. Of this ~ 350 million tonnes are organic wastes from agricultural sources; ~290 million tonnes are inorganic waste of industrial and mining sectors and ~ 4.5 million tonnes are hazardous in nature. Advances in solid waste management resulted in alternative construction materials as a substitute to traditional materials like bricks, blocks, tiles, aggregates, ceramics, cement, lime, soil, timber and paint. To safeguard the environment, efforts are being made for recycling different wastes and utilise them in value added applications. In this paper, present status on generation and utilization of both non-hazardous and hazardous solid wastes in India, their recycling potentials and environmental implication are reported and discussed in details.© Elsevie