Potential Applicability of Mg/Al-Layered Double Hydroxide (LDH) for Environmentally Friendly Chromium-based Leather Tanning

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 BOD5 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.

Lignin Demethylated by Protic Ionic Liquid as a Novel and Sustainable Chrome-Free Tanning Agent for Eco-Leather Production

“…The interaction sites of lignin with Al 3+ /Zr 4+ tanning agents were further demonstrated through XPS analysis. As shown in Figure b–f, Al 3+ /Zr 4+ could coordinate with phenolic –OH and CO bonds in LP since the binding energies of C–O–C and CO bonds in the O 1s spectra of LP-AZ were elevated compared to those of LP. , …”

“…As shown in Figure 8b−f, Al 3+ /Zr 4+ could coordinate with phenolic −OH and C�O bonds in LP since the binding energies of C−O−C and C�O bonds in the O 1s spectra of LP-AZ were elevated compared to those of LP. 49,50 Speculative Interactions between Tanning Agents and Collagen. Enhanced leather durability after tanning is usually generated by the cross-linking network between the tanning agent and leather matrix, based on a variety of interactions.…”

A review of the green chemistry approaches to leather tanning in imparting sustainable leather manufacturing

“…The goatskin treated with 40 g kg −1 MgAl–LDH and 20 g kg −1 BCS exhibited a shrinkage temperature of 94.0 ± 3.0 °C and the tensile strength achieved was considerably higher than the leather tanned with 20 g kg −1 BCS. 99 The Cr ion load in the effluent decreased from 99.6 to 35.0 mg L −1 along with a reduction of BOD5 and COD–Cr by 67% and 46%, respectively. Overall, Cr-syn/PAA/PMA complex provided the best tanning performance at the lowest water and chemical consumption.…”

“…96 Si nanoparticles modified with copolymer of methyl methacrylate and butyl acylate (SiNP–pMMA–BA) was also studied to reduce Cr consumption and also Cr load in the produced effluent. 97 Partial replacement of Cr with a nanocomposite of polycarboxylate and MMT, 98 and magnesium–aluminium-layered double hydroxide (MgAl–LDH) with 1 : 1 Mg : Al molar ratios with Cr, 99 were carried out to reduce the Cr load in the effluent.…”

Synthesis of layered double hydroxides: Investigating the impact of stirring conditions and reactor design parameters

“…LDHs were synthesized by the coprecipitation method at variable pH based on and adapapted from studies developed by Ref. [ [30] , [31] , [32] ]. LDHs were produced in a 2:1 Mg/Al ratio using two solutions; a solution A, containing Mg(NO 3 ) 2 .6H 2 O 1.42 M and Al(NO 3 ) 3 .9H 2 O 0.71 M in 434 mL of deionized water and a solution B composed of NaOH 2.2 M and Na 2 CO 3 1.2 M in 700 mL of deionized water.…”