Water reuse: An alternative to minimize the environmental impact on the leather industry

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.

Enhanced Adsorption of Textile Dyes by a Novel Sulfonated Activated Carbon Derived from Pomegranate Peel Waste: Isotherm, Kinetic and Thermodynamic Study

The rapid growth of the dye and textile industry has raised significant public concerns regarding the pollution caused by dye wastewater, which poses potential risks to human health. In this study, we successfully improved the adsorption efficiency of activated carbon derived from pomegranate peel waste (PPAC) through a single-step and surface modification approach using 5-sulfonate-salicylaldehyde sodium salt. This innovative and effective sulfonation approach to produce sulfonated activated carbon (S-PPAC) proved to be highly effective in removing crystal violet dye (CV) from polluted water. The prepared PPAC and S-PPAC were characterized via FESEM, EDS, FTIR and BET surface area. Characterization studies confirmed the highly porous structure of the PPAC and its successful surface modification, with surface areas reaching 1180.63 m2/g and 740.75 m2/g for the PPAC and S-PPAC, respectively. The maximum adsorption capacity was achieved at 785.53 mg/g with the S-PPAC, an increase of 22.76% compared to the PPAC at 45 °C. The isothermic adsorption and kinetic studies demonstrated that the adsorption process aligned well with the Freundlich isotherm model and followed the Elovich kinetic model, respectively. The thermodynamic study confirmed that the adsorption of CV dye was endothermic, spontaneous and thermodynamically favorable onto PPAC and S-PPAC.

Pollution patterns and their effects on biota within lotic and lentic freshwater ecosystems: How well contamination and response indicators correspond?

Aquatic environments are often severely polluted with chemical substances of anthropogenic origin, which can pose a potential threat to aquatic organisms and human health. In this study, patterns and sources of heavy metals (HMs, 6 metals) and polycyclic aromatic hydrocarbons (PAHs, 16 hydrocarbons), contamination indicators, environmental genotoxicity measures and metrics of ecological status in lotic and lentic ecosystems were collated for the first time. Chemical analysis has confirmed previously reported long-term contamination at certain study sites. The sediments of Lake Talkša, located in a city and characterized by exclusive anthropogenic pressure, exhibited the highest levels of contamination by both HMs and PAHs. Through positive matrix factorization (PMF) analysis, vehicle and industrial emissions were identified as the primary sources of HMs and PAHs. Our results revealed that frequencies of genotoxic aberrations were higher in river sites compared to lakes, with the highest genotoxic risk observed in the Nemunas River below industrial cities Alytus and Kaunas. Surprisingly, even the severely contaminated Lake Talkša showed only a "moderate" grade of genotoxic risk, highlighting the potential for adaptation of biota to long-term contamination especially in lentic ecosystems. The ecological quality status assessed by macroinvertebrate metrics, which may be sensitive to observed high biological contamination, appeared to be unrelated to contamination patterns. Consequently, to obtain the robust information on anthropogenic contamination and its effects, a combination of various assessment methods and metrics should be employed.

pH-Tunable electrokinetic movement of droplets

Manipulation and control of droplet motion in an electric field is of interest in biological systems, microfluidics and electrokinetic (EK) separation techniques. In this work, we show that the electrokinetic motion of oil-in-water (O/W) emulsions stabilized by an amphoteric surfactant can be controlled by changing the pH. Amphoteric surfactants carry both positive and negative head groups and change charge under the influence of changing pH, which allows them to impact the surface charge of droplets as a function of pH, and in extension their direction of motion in an electric field. Using a microfluidic system, we evaluate the effect of pH, surfactant concentration and droplet size on the EK velocity of droplets, which is a combination of electrophoresis (EP) and electro-osmotic flow (EOF). We show that by changing the pH from acidic to alkali, the direction of droplet motion in an external electric field changes. The magnitude of the EK velocity at acidic and neutral pH is not significantly altered as a result of the competition of the EP and EOF in the system, which generally have opposite directions. Our results are in good agreement with theoretical predictions for the droplet EP mobility and can thus serve as a verification of the theoretical descriptions. In addition to the pH, the surfactant concentration affects droplet EK velocity, most specifically at pH of 7 which is close to the isoelectric point of the surfactant monomers. At this pH, changing the surfactant concentration changes the direction of droplet motion due the competing effect of the EP and EOF at different surfactant concentrations. By increasing the droplet size, the magnitude of the EK velocity increases because of the larger local ζ-potential of the larger droplets as well as the wall-enhanced effect in the system. The results from this work can be applied to design on-chip droplet separation strategies based on pH variations and are relevant for systems in which pH gradients naturally occur, such as the human body.

Amino-functionalization of lignocellulosic biopolymer to be used as a green and sustainable adsorbent for anionic contaminant removal

In this work, natural biopolymer stemming from lignocellulosic peanut hull biomass was used as a green and low-cost adsorbent to eliminate anionic Congo red (CR) and Cr(VI) ions from aqueous sample. In order to enhance the removal performance, the lignocellulosic biopolymer was subjected to amino-modification by the graft copolymerization of (3-acrylamidopropyl) trimethylammonium chloride and N, N'-methylenebisacrylamide. The property of the prepared amino-functionalized biopolymer (AFB) was examined through FTIR, TG, SEM, particle size analysis, zeta potential determination and XPS. The adsorption efficacy of AFB for CR and Cr(VI) was tested at different pH, contact time and initial concentration. The kinetic, isotherm and thermodynamics investigations revealed that the uptakes of CR and Cr(VI) were the combination processes of chemical and physical interactions, and both endothermic in nature. The AFB exhibited good reusability without significant loss in adsorption capacity after five consecutive cycles. Mechanistic analysis indicated that the quaternary ammonium groups in AFB contributed a lot to the binding of anionic compounds through electrostatic attraction. In addition, n-π and hydrogen bonding while reduction and coordination were also responsible for the removal of CR and Cr(VI), respectively. The present study provides a favorable strategy for the removal of anionic contaminates in water by using green and sustainable lignocellulosic wastes.

Adoption of water reuse technologies: An assessment under different regulatory and operational scenarios

Water reuse technologies may alleviate the water scarcity problems that affect many world regions, but their adoption is still limited. In particular, key actors in the adoption of water reuse technologies are water utilities, that provide both urban water and wastewater treatment services. Water utilities are embedded in the urban water system, which includes several stakeholders (urban water users, citizens at large, the environment) that may drive or pose barriers to water reuse adoption. Therefore, to ensure a smooth introduction of water reuse technologies, it is fundamental to understand how water reuse interacts with the existing urban water system and impacts its stakeholders. This paper contributes to the ongoing debate on water reuse by conceptualizing the interaction between water reuse technologies and the urban water system and its stakeholders, and addressing the adoption decision of water utilities by assessing its economic and environmental consequences. Based on a review of literature, policy and other secondary documents, and on primary data coming from interviews with experts from a water utility operating in Southern Italy, the study models the utility's response to a shift from urban to reuse water. It then simulates how reuse water introduction impacts on the utility and other stakeholders of the water system, under various regulatory and operational scenarios defined through a thorough analysis of policy documents and literature. Results show that the adoption of water reuse reduces the utility's margin by cannibalizing urban water demand, but appropriate policy measures may enhance the economic sustainability of reuse. System-level performances, such as impact on freshwater savings, costs for users, effects on the public budget, are also assessed, showing how different regulatory options moderate the intensity of impacts for the different stakeholders of the water system. Furthermore, the adoption of reuse water by the most distant users is found to enhance the economic sustainability of reuse and positively impact the utility's margin.

Preventive strategies for reuse and recycling of wastewater within the HDG production

The hot-dip galvanizing consumes raw materials, supplies, and influence in the quantity/quality of wastewater, opening advantage for its segregation, reuse, and recycling. Therefore, the aim was to establish strategies for segregation, recycling, and preventives process of wastewater from a hot dip galvanizing enterprise (>10,000 t/year of galvanizing steel or gs). A mass balance (inputs-outputs by 1 t _gs), Sindex considering organic and inorganic parameters for segregation/recycling, and Water Pinch (Zn, COD, TDS) for reuse opportunities were determined. Flow diagrams were based on three scenarios that combine segregation/reuse/recycling, comparing saving water, energy, costs, and carbon dioxide equivalent (CO₂-eq) emissions. Results (mass balance) demonstrated that the water consumption in the rising phases (2,355.2 L/t _gs) corresponding to 95% of the total water demand. The best scenario combined reuse, segregation and recycling, which decreased up to 36% of treated wastewater, up to 40% of chemicals consumption, about 41% of treatment cost, close to 38% of energy consumed, and up to 17% of CO₂-eq emissions by wastewater treatment. Therefore, taking preventive measures without the need of technological changes (treatment) can achieve on efficient water management within of the hot-dip galvanizing production in developing countries.

Cleaner degreasing of sheepskins by the Yarrowia lipolytica LIP2 lipase as a chemical-free alternative in the leather industry

Conventional degreasing of skins and hides in the leather industry requires high amounts of organic solvents and detergents that cause environmental issues. In this study, the LIP2 lipase from the yeast Yarrowia lipolytica (YLLIP2) was shown to be effective in degreasing sheepskins, thus reducing the amount of harmful chemicals. Using 6 mg of lipase/kg of raw skin, successful degreasing was achieved in only 15 min at pH 8 and 30°C. ToF-SIMS mass spectra of chemically and enzymatically treated sheepskinsare consistent with a selective elimination process for the enzymatic treatment. Comparative SEM microscopy, ATR-FTIR spectroscopy and physicochemical analyses showed better properties of the enzymatically treated leather than those of the chemically treated leather. Effluent physicochemical parameters showed that the enzymatic treatment is a cleaner degreasing operation. Altogether, this work opens new horizons to use the YLLIP2 lipase as a more efficient alternative in the leather industry.

Nanomaterials to help eco-friendly leather processing

The leather industry converts the hide, a byproduct of slaughterhouses, into leather, a value-added product. This old industry generates wastes, causing environmental pollution. However, nanomaterials can help to decrease this problem. These tiny particles (1-100 nm) can replace chemicals in various steps of leather processing. This paper aims at giving an overview of the fundamentals of classical leather process and how nanomaterials can be applied in each step to obtain a more sustainable manufacturing. After a comprehensive literature review of journal articles, six steps were identified for potential for application of nanomaterials: unhairing, tanning, retanning, dyeing, fatliquoring, and finishing. With nano-oxides, polymers, and metals, it is feasible to reduce the amount of chemical products and also improve the properties of leather. Thus, it is possible to reach a more eco-friendly and effective process with the use of nanomaterials to turn hide/skins into finished leather.

Current technologies for post-tanning wastewater treatment: A review

Leather post-tanning is responsible for producing effluents that are difficult to treat due to several recalcitrant pollutants. Dyes, tannins, and fatliquoring agents are mainly related to this characteristic. This study, as the state-of-the-art, attempts to systematically review treatment technologies applied in recent years to the post-tanning effluents. The Scopus database was used to identify articles related to post-tanning pollutants removal. Through the review, Advanced Oxidation Processes (AOPs) and adsorption proved to be good alternatives to increase the effluent biodegradability when applied before biological treatment. AOPs and adsorption were also efficient for the final polishing of the effluents, to reach the regulation standards for disposal, as well as enzymatic treatment. Furthermore, Membrane Separation Processes demonstrated good applicability when the reuse of the treated effluent is aimed.

Magnetic water treatment in a wastewater treatment plant: Part I - sorption and magnetic particles

The application of magnetic sorption to treat wastewaters is nowadays seen as a potential industrial method. In this work we apply magnetite particles to remediate real wastewater samples, with several contaminants competing for the same active sorption center at the same time. We also apply our studies at three different sampling points of a Wastewater Treatment Plant. In general terms, magnetite particles have shown a very good behaviour concerning the reduction of detergents and COD, while phosphates and total nitrogen, and the majority of heavy metals are high to moderately removed. The influence of the type of wastewater (i.e., sampling point) has also shown to be important especially for high concentration of contaminants.

Water reclamation and reuse

Literature published in 2019 pertinent to water reclamation and reuse has been classified into five sections: safe reuse, treatment technologies, management, assessment, and case studies. Membranes have been widely applied in integrated processes to polish secondary effluent and achieve high-quality reclaimed water. Increased efforts have also been made to facilitate feasible and safe water reuse. PRACTITIONER POINTS: This article summarizes literature published in 2019 pertinent to water reclamation and reuse. Water reclamation and reuse can be classfied into five sections: safe reuse, treatment technology, management, assessment, and case studies. Membranes were widely used in integrated processes for the production of high-quality reclaimed water.

Wastewater from leather tanning and processing in Palestine: Characterization and management aspects

Leather manufacturing industry has major environmental impacts. Characterization of tannery's wastewater (WW) is a key step in the management of wastewater released from various processes. This study presents some physicochemical characteristics measured in wastewater. It compares the pollution loads released from both goat and cow hides processing. The main pollution characteristics of wastewater released from two local tanneries were determined experimentally, through analyzing real samples of industrial discharges. These include chemical oxygen demand (COD), total solids (TS), total dissolved solids (TDS), total suspended solids (TSS), pH, and the concentrations of chloride, ammonia (NH₃) and chromium in both states, Cr (III) and Cr (VI). Characterization of such processes effluents assists in identifying waste generation rates and discharges, and then in recommending cleaner production options. The results shows that the amount of WW produced in the local Palestinian tanneries is much lower than tanneries worldwide, whereas it is more concentrated with pollutants. Liming process has the highest COD and the highest pH value, where tanning process releases WW highly concentrated with chromium. Real process measurements and mass balance calculations indicated that the chromium uptake efficiency is only 46.6%. Such a low efficiency indicates that cleaner production measures are essential in local tanneries.

Leather Thermal and Environmental Parameters in Fire Conditions

The thermal decomposition of leather-product combustion produces some inflammable and harmful compounds after tanning, fat liquoring, dyeing, and finishing processes. These organic compounds are ignited and release a lot of toxic gases and smoke in fire conditions, polluting the atmosphere air. On this account, it is very important to know leather safety performance for fire prevention. The flammability and thermal stability of types of leather at thermal expositions stimulating fire conditions were analyzed. Five types of leather were used in experimental testing, four of animal origin and an artificial one. Results showed that, in the analyzed heat exposure, the highest average heat-release rate (174 kW/m2) and smoke generation, and the lowest temperature of the beginning of thermal decomposition, were recorded for the artificial leather. Leather flammability essentially depends on the type of applied energy stimulus, as well as hide composition and origin. A possible cause for differences in the obtained results of the leather analyses is the percentage of certain leather components and their chemical composition.

A novel carbon monoxide fed moving bed biofilm reactor for sulfate rich wastewater treatment

In this study, a moving bed biofilm reactor was used for biodesulfuruization using CO as the sole carbon substrate. The effect of hydraulic retention time (HRT), sulfate loading rate and CO loading rate on sulfate and CO removal was examined. At 72, 48 and 24 h HRT, the sulfate removal was 93.5%, 91.9% and 80.1%, respectively. An increase in the sulfate loading reduced the sulfate reduction efficiency, which, however, was improved by increasing the CO flow rate into the MBBR. Best results in terms of sulfate reduction (>80%) were obtained for low inlet sulfate and high CO loading conditions. The CO utilization was very high at 85% throughout the study, except during the last phase of the continuous bioreactor operation it was around 70%. An artificial neural network based model was successfully developed and optimized to accurately predict the bioreactor performance in terms of both sulfate reduction and CO utilization. Overall, this study showed an excellent potential of the moving bed biofilm bioreactor for efficient sulfate reduction even under high loading conditions.