Diagnosing the environmental impacts of typical fatliquors in leather manufacture from life cycle assessment perspective

The environmental impacts of typical fatliquors were diagnosed by the life cycle assessment of industrial production and use(post-tanning)processes.Life cycle impact assessment and sensitivity analysis showed that fatliquor and fatliquoring operation were the major contributors to the environmental impacts of post-tanning because a large amount of fatliquors was consumed during fatliquoring operation.The environmental impacts of fatliquors decreased in the following order:chlorinated paraffin(CP)>sulfonated rape oil(SNR)>sulfated rape oil(SR)>phosphated rape oil(PR)>oxidized-sullfited rape oil(OSR).Sulfuric acid,fuming sulfuric acid,and chlorine used for fatliquor modification gave the main contribution to most impact categories for SR,SNR,and CP production,whereas rape oil contributed the most for PR and OSR production.OSR use process reduced the primary energy demand,abiotic depletion potential,and global warming potential by 38.5%,56.0%,and 48.5%,respectively,compared with CP use process.These results suggested that biomass-derived fatliquors,especially oxidized-sulfited and phosphate modified fatiiliquors,helped reduce the environmental burdens in leather manufacturing.

Effects of bactericide-protease interactions on the protease-assisted soaking performance

Protease-assisted soaking has received increasing attention in recent years.However,few reports have elaborated on the effect of bactericides,which are used to protect raw hides from microbial damage in the soaking process,on the performance of protease-assisted soaking.Here we investigate the effects of three bactericides,namely,2-methyl-4-isothiazolin-3-one(MIT),sodium propyl 4-hydroxybenzoate(SPHB)and cetyl trimethyl ammonium bromide(CTAB),on the catalytic activity of protease.MIT and SPHB have little effect on the proteolytic activity,whilst CTAB has a negative effect.Fluorescence spectroscopy,synchronous fluorescence spectroscopy,molecular docking and molecular dynamics simulation were used to analyse the bactericide-protease interaction.The data reveal that MIT and SPHB are bound to the non-catalytic sites of protease,whilst CTAB affects the catalytic triad of protease.Furthermore,the protease and bactericides were used alone,simultaneously and sequentially in the soaking process,and their soaking performances were evaluated.The evaluation shows that the use of protease increases the microorganisms in the soaking float,and MIT exhibits the best bactericidal effect.The simultaneous use of protease and MIT effectively inhibits bacteria and scarcely affects the removal of unstructured proteins from hides and the attack on epidermis by protease.These findings contribute to a better understanding of the scientific use of protease with other auxiliaries in soaking.

A deeper exploration of the relation between sulfonation degree and retanning performance of aromatic syntans

It is well‑known that the sulfonation degree(DS)of aromatic syntan is an important factor affecting its retanning performances.But the quantitative relation between DS and syntan property and the influencing mechanism of DS on syntan property are not clarified.In this work,five phenolic formaldehyde syntans(PFSs)with the same polym‑erization degree but varying DS were prepared to investigate the effect of DS on the properties of syntan and crust leather.It was found that the absolute value of zeta potential and the particle size of PFS decreased with increasing DS in aqueous solution.Molecular dynamic simulation results proved that the DS of PFS was a major contributor to electrostatic interaction and hydrogen bonding in the PFS–water system and greatly affected the aggregation and dispersion of PFS in aqueous solution.The PFS with a low DS was prone to aggregate to large particles in aqueous solution because of low intermolecular electrostatic repulsion and less hydrogen bonds and therefore can be used to increase the thickness and tightness of leather.The PFS with a high DS presented a small particle size with more anionic groups in aqueous solution,thereby sharply decreasing the positive charge of leather surface and facilitat‑ing the penetration of the post‑tanning agents into the leather.These results might be scientifically valid for rational molecular design of syntans and more productive use of syntans in leather making.

Diagnosing the environmental impacts of typical fatliquors in leather manufacture from life cycle assessment perspective

The environmental impacts of typical fatliquors were diagnosed by the life cycle assessment of industrial production and use(post-tanning)processes.Life cycle impact assessment and sensitivity analysis showed that fatliquor and fatliquoring operation were the major contributors to the environmental impacts of post-tanning because a large amount of fatliquors was consumed during fatliquoring operation.The environmental impacts of fatliquors decreased in the following order:chlorinated paraffin(CP)>sulfonated rape oil(SNR)>sulfated rape oil(SR)>phosphated rape oil(PR)>oxidized-sulfited rape oil(OSR).Sulfuric acid,fuming sulfuric acid,and chlorine used for fatliquor modification gave the main contribution to most impact categories for SR,SNR,and CP production,whereas rape oil contributed the most for PR and OSR production.OSR use process reduced the primary energy demand,abiotic depletion potential,and global warming potential by 38.5%,56.0%,and 48.5%,respectively,compared with CP use process.These results suggested that biomass-derived fatliquors,especially oxidized-sulfited and phosphate modified fatiliquors,helped reduce the environmental burdens in leather manufacturing.

Evaluation and improvement of the oxidative stability of leather fatliquors

Fatliquor oxidation may give leather unpleasant odor,and excessive amounts of Cr(VI)and volatile organic com-pounds.The accurate evaluation and improvement of the oxidative stability of fatliquors are of great significance to high-quality leather manufacturing.We proposed a set of practical methods for evaluating the oxidative stability of fatliquors on the basis of oxidation induction time,change in iodine value(∆IV),and change in acid value(∆AV)under accelerated oxidation conditions(at 100°C with 10 L/h of air).Oxidation induction time is a highly sensitive marker for quantifying the oxidative stability of fatliquors,and∆IV and∆AV that are low cost and easy to operate are useful in evaluating the oxidative stability of fatliquors when the oxidation induction time is less than 22 h.The number of double bonds in fatliquors is an important factor affecting oxidative stability.The sulfation modification of fatliquors that greatly reduces double bonds and the addition of antioxidants,especially butylated hydroxyanisole and butylated hydroxytoluene,markedly improve oxidative stability of fatliquors.

Factors affecting mass transfer of protease in pelt during enzymatic bating process

Bating pelt with protease is an important process,which removes unwanted non-collagenous proteins from the pelt and moderately disperse hide collagen network.However,the grain surface,may be excessively hydrolyzed during bating due to the longer retention time of protease in the grain than in the middle layer caused by the low mass transfer rate of protease in pelt.Here,the effects of protease dosage,common auxiliaries and molecular weight of protease on protease transfer during bating were investigated so that we can find the key points to avoid excessive collagen damage,particularly in the grain.Observably,increasing protease dosage led to faster protease transfer and softer leather,but along with more considerable grain damage.Using penetrating agent JFC(fatty alcohol-polyoxyethylene ether)and ammonium sulfate enhanced protease transfer and simultaneously alleviated collagen damage due to the decrease in interfacial tension and electrostatic attraction between protease and pelt,respectively.Additionally,proteases with lower molecular weight transferred faster in pelt,which suggests that a potential strategy to solve the conflict between the mass transfer and the reaction of protease in pelt might be to produce/employ smaller bating proteases.

An exploration of enhancing thermal stability of leather by hydrophilicity regulation:effect of hydrophilicity of phenolic syntan

Effect of retanning on the thermal stability of leather is eliciting increasing attention. However, the relationship between the hydrophilicity of retanning agents and the heat resistance of leather and the corresponding mechanism remain unclear. Herein, phenolic formaldehyde syntans (PFSs) were selected as models to explore the effect of the hydrophilicity of retanning agents on the thermal stability of retanned leather. The thermal stability of leather was closely correlated to the hydrophilic group content (sulfonation degree) of PFSs. As the sulfonation degree increased, the water absorption rate of PFSs and their retanned leathers decreased, whereas the thermal stability of leather increased. Molecular dynamics simulation results proved that the introduction of PFSs could reduce the binding ability of collagen molecules with water and thus decreased the water molecules around the PFS-treated collagen. These results may provide guidance for the tanners to select retanning agents reasonably to improve the thermal stability of leather.