Cadmium is known to be toxic for living organism even if it is present in low levels. Generally it is associated with zinc and copper minerals and is produced as a byproduct of these industries. It enters the environment from electroplating, smelting, alloy manufacturing, pigments, plastic, cadmium-nickel batteries, fertilizers, pesticides, mining, pigments and dyes, textile operations and refining industries. Various ways of cadmium removal are: precipitation, ion exchange, solvent extraction and adsorption. The present review specifically describes various types of adsorbents which have been used for removing cadmium from aqueous solutions. General emphasis has been on the utilization of agricultural, industrial wastes and low cost synthetic oxides as adsorbents. In most of the studies batch mode data has been evaluated by determining the kinetic, isothermic and thermodynamic parameters. A number of studies have also addressed the mechanism of adsorption process employing instrumental techniques such as XRD, FTIR, SEM etc. Modeling of column data has also been reported by some researchers. More attention needs to be given for regeneration/reuse/ safe disposal of the loaded adsorbents wherein the data are insufficient. The engineering aspects also need attention for commercial application of various adsorbents.

About 70% of total electrical energy is generated from thermal power plants in India which in turn release about 160 Mt of fly ash as solid waste annually. Transportation and disposal of such a huge amount of fly ash is a major problem faced by the power plants. Presently fly ash is transported as lean slurry in pipe lines requiring about 80 to 85% of water with high energy input. A major impediment in high volume transportation of fly ash is its high specific gravity as compared to that of water. The objective of the present study was to evaluate the rheological characteristics of high concentration fly ash slurry with and without a chemical reagent at varying temperature environment to facilitate smooth flow of materials in the pipelines. Six different composition of fly ash slurry samples were considered for investigation. The main constituents of the slurry were fly ash, water, a cationic surfactant, and a counter-ion. Detailed rheological properties were determined using a cylindrical coaxial rotational rheometer at shear rates varying from 25s 21 to 1000s 21 for 40% solid concentration (by weight). Temperature was varied from 20uC to 40uC for all the shear rates investigated. Test results showed that all the slurries exhibited shearthinning behaviour in the presence of the surfactant. The influence of cationic tenside on drag reduction of fly ash slurry was also studied. The distinctive reduction of surface tension on colloidal dispersion characteristics of the fly ash slurry was observed in the presence of the tenside. It revealed that the slurry developed in the above manner has a potential to be transported through pipelines with minimal energy consumption.