Recycling of Reclaimed-water from Tannery Effluent for High Exhaustion Chrome Tanning

摘要

The reclaimed-water for this study was the treated tannery effluent meeting the requirements specified in GB8978-1996, which is between the fresh water used for leather making and the effluents from all the process. It contains some inorganic ions such as Cl~-, SO_4 ~(2-), Na~+, Ca~(2+), Mg~(2+) and higher CODc_r & SS values and would pollute environment if it is discharged directly. In this study, the influences of the contents of COD & SS in the reclaimed- water on pickling and chrome-tanning along with the feasibility of recycling the reclaimed-water for high exhaustion chrome tanning were investigated by tanning practices with cattle hides. The uptake of chromium was 81.86% when the contents of CODc_r & SS in the reclaimed-water reached 186.0mg/L and 120.0mg/L respectively, and yet the uptake of chromium had reached 90% above and the shrinkage temperature of the leathers was so high that leathers wouldnlt shrink in boiling water for 3 minutes while 0.6% tanning auxiliaries as DC or CF based on bated pelt weight were added at later phase of chrome-tanning. Also the penetration and distribution of chromium in the interior of wet blues were homogeneous, and there was no deposition of calcium or magnesium salts on the surface of leathers through SEM and EDAX. At last, the physical and mechanical properties of crust leather reached to shoe upper leather standard. All the results suggested that it is a viable proposal of high-exhaustion of chromium with the reclaimed-water from tannery.