Removal and Stabilization of Chromium Ions from Industrial Effluents

Laboratory experiments were designed to investigate the removal of chromium ions from industrial effluent by stabilizing in silica sand, acting as adsorbents, to prevent leaching. Removal of chromium (III) ions from industrial effluents using silica sand (originated from the river of Ravi) was studied to optimize the physicochemical conditions for maximal removal. The range of pH and temperature was adjusted to achieve maximal removal of metal ions. The initial and fin al concentration of chromium was measured by atomic absorption spectroscopy. The residual concentration of chromium in waste water after treatment was less than 1.0 mg/1 which is the value recommended by National Environment Quality Standards (NEQS). Maximal removal (94-96 %) of chromium is achieved with pH 10 and at a temperature of 28 degrees C. Under optimized conditions within temperature range of 301-315 K the values of Delta h, Delta S and Delta G(301) K for 100 ppm solution are (-94.41 +/- 0.48) kJ/mol, (-287.02 +/- 1.56) J/mol and (-7.93 +/- 0.60) kJ/mol, respectively, and for 150 ppm solution thermodynamic entities are Delta I = (-74.57 +/- 0.20) kJ/mol, Delta S = (-287.39 +/- 0.66) J/mol and Delta G(301 K) = (-6.88 +/- 0.40) kJ/mol. The removal of chromium metal ions using silica sand is followed by its stabilization to minimize the desertion of sorbed metal ions under changed physiochemical conditions during fin al disposal. The stabilization was obtained by converting the silica sand along with the sorbed chromium ions into the glass matrix. Due to the large amount of glass network former in sand, it is cheap and proved as a promising basic material for glass. The characteristics of the matrix show no leachibility of chromium ions.