Efficient Triazine Derivatives for Collagenous Materials Stabilization

Characterisation and tanning effects of purified chestnut and sulfited quebracho extracts

Vegetable tannins are environmentally friendly tanning agents. However, they generally impart a dark colour to the tanned leather and highly contribute to the organic load in wastewaters. In this study, we employed a purification protocol separately on chestnut tannin (CT) and sulfited quebracho tannin (QT) to obtain the purified fractions (PCT and PQT). These samples were characterised by GPC, 1H NMR, 13C NMR, FT-IR, and HPLC-DAD techniques and applied for tanning tests. Through the purification process, non-tannin components and smaller molecules such as gallic acid, glucopyranose, and catechin were effectively removed from CT and QT, which consequently led to the reduced moisture content, pH value, and lighter colour of purified fractions. The crust leathers processed with PCT and PQT showed desirable light shades. Moreover, the organic loads in PCT and PQT tanning wastewater were reduced by 13.5% and 19.1%, respectively, when compared to those in traditional CT and QT tanning wastewater. Additionally, the physical and mechanical characteristics of crust leathers processed with PCT and PQT were comparable to those processed with CT and QT. Thus, purification of vegetable tannins may serve as a feasible strategy for producing light-colored vegetable-tanned leather while minimizing organic pollutant discharge during the vegetable tanning process.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s42825-024-00171-9.

Chitosan as a Bio-Based Ligand for the Production of Hydrogenation Catalysts

Bio-based polymers are attracting increasing interest as alternatives to harmful and environmentally concerning non-biodegradable fossil-based products. In particular, bio-based polymers may be employed as ligands for the preparation of metal nanoparticles (M(0)NPs). In this study, chitosan (CS) was used for the stabilization of Ru(0) and Rh(0) metal nanoparticles (MNPs), prepared by simply mixing RhCl3 × 3H2O or RuCl3 with an aqueous solution of CS, followed by NaBH4 reduction. The formation of M(0)NPs-CS was confirmed by Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC), Thermal Gravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Analysis (EDX), Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). Their size was estimated to be below 40 nm for Rh(0)-CS and 10nm for Ru(0)-CS by SEM analysis. M(0)NPs-CS were employed for the hydrogenation of (E)-cinnamic aldehyde and levulinic acid. Easy recovery by liquid-liquid extraction made it possible to separate the catalyst from the reaction products. Recycling experiments demonstrated that M(0)NPs-CS were highly efficient up to four times in the best hydrogenation conditions. The data found in this study show that CS is an excellent ligand for the stabilization of Rh(0) and Ru(0) nanoparticles, allowing the production of some of the most efficient, selective and recyclable hydrogenation catalysts known in the literature.

May 1,3,5-Triazine derivatives be the future of leather tanning? A critical review

Leather is produced by a multi-step process among which the tanning phase is the most relevant, transforming animal skin collagen into a stable, non-putrescible material used to produce a variety of different goods, for the footwear, automotive, garments, and sports industry. Most of the leather produced today is tanned with chromium (III) salts or alternatively with aldehydes or synthetic tannins, generating high environmental concern. Over the years, high exhaustion tanning systems have been developed to reduce the environmental impact of chromium salts, which nevertheless do not avoid the use of metals. Chrome-free alternatives such as aldehydes and phenol based synthetic tannins, are suffering from Reach restrictions due to their toxicity. Thus, the need for environmentally benign and economically sustainable tanning agents is increasingly urgent. In this review, the synthesis, use and tanning mechanism of a new class of tanning agents, 1,3,5-triazines derivatives, have been reported together with organoleptic, physical mechanical characteristics of tanned leather produced. Additionally environmental performance and economic data available for 1,3,5-triazines have been compared with those of a standard basic chromium sulphate tanning process, evidencing the high potentiality for sustainable, metal, aldehyde, and phenol free leather manufacturing.

Agri-Food Wastes for Bioplastics: European Prospective on Possible Applications in Their Second Life for a Circular Economy

Agri-food wastes (such as brewer's spent grain, olive pomace, residual pulp from fruit juice production, etc.) are produced annually in very high quantities posing a serious problem, both environmentally and economically. These wastes can be used as secondary starting materials to produce value-added goods within the principles of the circular economy. In this context, this review focuses on the use of agri-food wastes either to produce building blocks for bioplastics manufacturing or biofillers to be mixed with other bioplastics. The pros and cons of the literature analysis have been highlighted, together with the main aspects related to the production of bioplastics, their use and recycling. The high number of European Union (EU)-funded projects for the valorisation of agri-food waste with the best European practices for this industrial sector confirm a growing interest in safeguarding our planet from environmental pollution. However, problems such as the correct labelling and separation of bioplastics from fossil ones remain open and to be optimised, with the possibility of reuse before final composting and selective recovery of biomass.

Boosting physical-mechanical properties of adipic acid/chitosan films by DMTMM cross-linking

In this paper we present a novel strategy to easily prepare biodegradable chitosan derived films as new packaging systems. Combination of chitosan, adipic acid and 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride (DMTMM) allowed to obtain high-performing cross-linked films. Biobased glycerol was employed as plasticizer. An in-depth study was performed on ten different samples in order to evaluate the role of DMTMM as cross-linking agent. Experimental data showed that 15 wt% of DMTMM enhanced moisture content and moisture uptake (10.42% and 11.11%), water vapor permeability (0.13 10^-7 g m^-1 h^-1 Pa^-1) and good UV barrier properties. Additionally, 30 wt% of DMTMM significantly increased the tensile strength of films up to 83 MPa and elongation at break values reached 39.7%. Thermogravimetric, IR, XRD and SEM analysis confirmed that physical-mechanical properties of the obtained films were considerably improved, due to cross-linking by DMTMM, demonstrating promising properties for packaging applications.

Characterization of Wet Olive Pomace Waste as Bio Based Resource for Leather Tanning

Olive mill wastes represent an important environmental problem. Their high phenol, lipid, and organic acid concentrations turn them into phytotoxic materials. Specifically, wet olive pomace (WOP) is the waste generated in the two-phase continuous extraction process. WOP is a paste with around 60% water. The total volume of WOP generated is around 0.25 L/kg of olives processed. Its current waste management practices result in environmental problems as soil contamination, underground seepage, water-bodies pollution, and foul odor emissions. Some valorization alternatives include composting, biological treatments, direct combustion for energy production, or direct land application. The leather industry is making great efforts to apply cleaner processes while substituting chemical products for natural products. In this way, different alternatives are being studied, such as the use of zeolites, triazine derivatives, grape seed extract, olive leaf extract, etc. In this work, the use of wet olive pomace is presented as a possible alternative to conventional vegetable tannins (mimosa, quebracho, chestnut, etc.). Although different projects and studies have been developed for the valorization of olive mill wastes, there is completely a new approach to the WOP application for tanning purposes. This study shows that WOP has a significant number of polyphenolic substances, so it has a great potential to be used as a tanning agent. Specifically, this study has been able to determine that, of the polyphenols present in WOP, 39.6% correspond to tannins that are capable of tanning the skin. Additionally, it contains 14.3% non-tannins, that is, molecules that by themselves do not have the capacity to tan the leather but promote the tanning mechanism and improve the properties of the tanned leather.

Recent Advancements in Plastic Packaging Recycling: A Mini-Review

Today, the scientific community is facing crucial challenges in delivering a healthier world for future generations. Among these, the quest for circular and sustainable approaches for plastic recycling is one of the most demanding for several reasons. Indeed, the massive use of plastic materials over the last century has generated large amounts of long-lasting waste, which, for much time, has not been object of adequate recovery and disposal politics. Most of this waste is generated by packaging materials. Nevertheless, in the last decade, a new trend imposed by environmental concerns brought this topic under the magnifying glass, as testified by the increasing number of related publications. Several methods have been proposed for the recycling of polymeric plastic materials based on chemical or mechanical methods. A panorama of the most promising studies related to the recycling of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polystyrene (PS) is given within this review.