Assessment of heavy metals and rheological characteristics of coal ash samples in presence of some selective additives

摘要

The huge quantity of coal ash produced in Indian thermal power plants is disposed of in ash landfills or ash ponds. The deposition of ash in ash ponds through conventional lean slurry form is viewed as a major potential release of many environmentally sensitive heavy metals due to possible contamination with ground water. An attempt has been made in this paper to assess the leachability of the heavy metals such as Cu, Pb, Ni, Co, Zn, Cd, Hg and As from two Indian power plant ash samples in the presence of some selective low-cost additives. The additives used for the study were sodium silicate (Na2SiO3 center dot 5H(2)O), Reetha fruit (botanical name: Sapindus Mukorossi) extract, banana leaf extract, Aloe vera juice and active carbon. By adopting short duration (7 days) batch leaching test and toxicity characteristics leaching procedure (TCLP), the behaviour of various heavy metal ions released in water influenced by small dosage of these selective additives has been analysed. By introducing the same additives, the rheological behaviour of the two fly ash samples at high solids concentration (C (W) = 55-67.5 % by weight) was carried out using a HAAKE rotational rheometer (model: RheoStress 1, Thermo Fisher Scientific). The influence of small dosage of these additives on rheological parameters of the ash-water slurry has been discussed.