Potential Applicability of Mg/Al-Layered Double Hydroxide (LDH) for Environmentally Friendly Chromium-based Leather Tanning
Ping Zhao, Dangge Gao, Hui Zhang, Bin Lyu, Jianzhong Ma, Sherif A. Younis, Ki‐Hyun Kim
Abstract
In this work, a highly efficient tanning agent was developed by combining magnesium–aluminum-layered double hydroxide (MgAl-LDH) with different Mg:Al molar ratios and 2% chrome (MgAl-LDH-2%Cr composite). MgAl-LDH-2% Cr (at 1 Mg:1 Al molar ratio for a 4-hour aging period) showed a much higher leather shrinkage temperature (Ts) of up to 93.8 °C upon tanning than a bare 2% chrome tanning agent (74.2 °C). The use of MgAl-LDH-2%Cr in the tanning process was also environmentally friendly, as it helped reduce the leaching amount of chromium ions in the tanning effluent (e.g., from 99.6 to 35.0 mg L –1 ), accompanied by the reduction of BOD 5 and COD-Cr by 67% and 46%, respectively (relative to the conventional chrome tanning process). The improved tanning effects can possibly be accounted for by the adsorption of a positive chromium complex onto MgAl-LDH laminates with hydroxyl groups to obtain a better tanning effect through the penetration of chromium into skin collagen fibers.