Mechanistic approach of tannery wastewater and sulfadiazine mutual toxicity in wheat (Triticum aestivum L.) and mitigation through exogenous application of gallic acid.

Excessive release of chromium (Cr) from the tanning industry and antibiotics from livestock caused severe hazards to humans. Gallic acid (GA 10 mM) alleviated alone/combined SDZ 30 mg kg-1 and TWW 40, 60, and 100% stress in wheat. GA (10 mM) decreased the TSP 12 and 13%, TFAA 8 and 10%, TSS 14 and 16%, RS 18 and 16%, and NRS 11 and 9% in shoots and grains under SDZ + TWW (30 mg kg-1+100%), compared without foliar. GA (10 mM) declined the MDA 20 and 31, EL 13 and 36%, H2O2 17 and 15%, O2•- 10 and 11% in leaves and roots, under combined SDZ + TWW (30 mg kg-1+100%), compared without foliar. GA (10 mM) improved the POD 106 and 30%, SOD 145 and 31%, CAT 78, and 35%, APX 100 and 25% in leaves and roots under combined SDZ + TWW (30 mg kg-1+100%), compared without foliar application. Considerably GA (10 mM) reduced total Cr 18, CrIII 20, and CrVI 50% in roots and shoots 19, 41, and 48%, and grains 15, 27, and 29% respectively, under combined SDZ + TWW (30 mg kg-1+100%) stress, compared without foliar. Overall, GA boosted the wheat growth, physiology, and defence system by inhibiting the combined SDZ + Cr toxicity.

Evaluating the efficacy of vermicomposted products in rain-fed wetland rice and predicting potential hazards from metal-contaminated tannery sludge using novel machine learning tactic.

The study assessed the ecotoxicity and bioavailability of potential metals (PMs) from tannery waste sludge, alongside addressing the environmental concerns of overuse of chemical fertilizers, by comparing the impacts of organic vermicomposted tannery waste, chemical fertilizers, and sole application of tannery waste on soil and rice (Oryza sativa L.) plants. The results revealed that T3, which received high-quality vermicomposted tannery waste as an amendment, exhibited superior enzymatic characteristics compared to tannery sludge amended (TWS) treatments (T8, T9). After harvesting, vermicomposted tannery waste treatment (T3) showed a more significant decrease in PMs bioavailability. Accumulation of PMs in rice was minimal across all treatments except T8 and T9, where toxic tannery waste was present, resulting in a high-risk classification (class 5 < 0.01) according to the SAMOE risk assessment. Results from Fuzzy-TOPSIS, ANN, and Sobol sensitivity analyses (SSA) further indicated that elevated concentrations of PMs (Ni, Pb, Cr, Cu) adversely impacted soil-plant health synergy, with T3 showing a minimal risk in comparison to T8 and T9. According to SSA, microbial biomass carbon and acid phosphatase activity were the most sensitive factors affected by PMs concentrations in TWS. The results from the ANN assay revealed that the primary contributing factor of toxicity on the TWS was the exchangeable fraction of Cr. Correlation statistics underscored the significant detrimental effect of PMs' bioavailability on microbial and enzymatic parameters. Overall, the findings suggest that vermicomposting of tannery sludge waste shows potential as a viable organic amendment option in the near future.

New plant polyphenol-derived tannic acid-based chromium-free tanning agent for sustainable and clean leather production.

This study aimed to prepare a new bio-based chromium-free tanning agent. The green epoxide monocase ethylene glycol diglycidyl ether (EGDE) was grafted with tannic acid (TA) derived from natural plant using the one-pot method to synthesize new plant polyphenol-derived tannic acid-based chromium-free tanning agents (TA-EGDE) with abundant terminal epoxides. FTIR, 1H NMR, XPS, GPC, SEM, and other analytical techniques were used to characterize tanning agents. These consequences manifested that EGDE was successfully grafted with the phenol hydroxyl group of TA. The epoxide value of TA-EGDE showed a tendency to increase and then decrease with increasing EGDE dosage, and the epoxide value of TA-EGDE-2 attained a maximum of 0.262 mol/100 g. GPC analysis showed that the formula weight of the prepared TA-EGDE was partially distributed above 5000 Da. The tanning experiment demonstrated that the shrinkage temperatures (Ts) of the TA-EGDE-tanned leathers were all higher than 81.5 °C. Compared with the traditional commercial chromium-free tanning agent (F-90, TWS), TA-EGDE-tanned leathers exhibited higher Ts and better mechanical properties. The TA-EGDE prepared in this study not only has ecological environmental protection but also provides finished leather with good moisture, heat resistance, and mechanical properties.

Sustainable leather tanning: Enhanced properties and pollution reduction through crude protease enzyme treatment.

In this study, proteolytic bacteria, particularly Pseudomonas aeruginosa strain SM4 (OQ349573), were isolated from tannery solid waste dumping yard soil and employed to produce extracellular protease enzymes. The bacteria exhibited optimal growth after 30 h of incubation at 37 °C and pH 7. Under conditions of 55 °C, pH 8, and a substrate concentration of 2 %, the crude enzyme displayed its highest activity at 105 UmL-1. Notably, the produced crude enzyme showed no discernible inhibitory effects on detergents, metal salts, or organic solvents. Application of the crude protease at concentrations of 3 % and 2 % in chrome tanning of goatskins (GS) and cowhides (CH), respectively, yielded significant reductions of 35 % and 30 % in chromium and other post-tanning chemicals compared to conventional processes. Despite the 30 to 35 % reduction in tanning and post-tanning chemicals, the uptake of chrome and associated chemicals by crust leather was higher than observed in conventional processes. Chromium content analysis of the effluent revealed an 81 % reduction during piloting in real industrial operations, accompanied by reductions of about 46 % in BOD and COD pollution loads. The finished leather obtained from the enzymatic process exhibited superior mechanical properties, including higher tensile strengths (210 and 195 kg cm-2), stitch tear (92 and 165 kg cm-1), grain crack load (28 and 32 kg), and distension (73 and 62 mm) for GS and CH, respectively, surpassing or closely aligning with standard values and those obtained in conventional processes.

Approach towards sustainable leather: Characterization and effective industrial application of proteases from Bacillus sps. for ecofriendly dehairing of leather hide.

Tanneries are one of the most polluted industries known for production of massive amount of solid and liquid wastes without proper management and disposal. In this project we demonstrated the ecofriendly single step dehairing of leather hides with minimum pollution load. In this study, Bacillus species (Bacillus paralicheniformis strain BL.HK, Bacillus cereus strain BS.P) capable of producing proteases was successfully isolated by employing the new optimized selective media named M9-PEA as confirmed by 16sRNA genes sequencing. Sequence of 1493 bp long 16S rRNA genes of Bacillus paralicheniformis strain BL.HK and Bacillus cereus strain BS. P was submitted to GenBank under the accession number OP612692.1, OP612721.1 respectively The Bacillus paralicheniformis strain BL.HK, Bacillus cereus strain BS.P produced extracellur proteases of 28 and 37 KDa as resolved by SDS-PAGE respectively. The enzymes showed temperature optima at 50 °C and 55 °C and pH optima at 8.5, 9.5 respectively. The Proteases of Bacillus paralicheniformis strain BL.HK, Bacillus cereus strain BS.P were employed for dehairing of animal hides. The process resulted in significant removal of interfibriller substances without damage to collagen layer after one hour treatment, which was confirmed by histology, scanning electron microscopy. The quantification of various skin constituents (collagen, uronic acid, hexosamines, and GAGs) and pollution load parameters revealed that enzymatic treatment are more reliable. The results of skin application trials at industrial level with complete elimination of chemicals remark the biotechnological potential of these proteases for ecofriendly dehairing of animal hides without affecting the quality of the leathers produced.

Development of masked silica tanning system for sustainable leather production.

Amid mounting pressure on the long-term recyclability of chromium in tanned leather and the associated environmental hazards, the quest for an alternative, cleaner tanning system has gained tremendous momentum. In this context, our study explores the remarkable potential of silicates as a versatile platform for skin/hide tanning, circumventing the inherent risks and ecological threats posed by chromium exposure and leaching. We present an alternative approach of using a silica-based tanning system, employing a Taguchi model, to optimize a masked silica (MaSil) tanning product/process for achieving effective collagen stabilization. Our results demonstrate the significant advancements made in hydrothermal denaturation temperature, reaching an impressive 79 °C through precise Taguchi parameters-5% SiO2, masked with 0.3 mole of citrate salt, and a tanning process fixation pH of 4.5. Notably, the mechanical strength analysis reveals compliance with the stringent upper leather recommendation standards, validating the practicality and quality of MaSil crust leather. Moreover, our research highlights the unprecedented environmental benefits of the first reported application of Taguchi's approach to the MaSil tanning system. The developed tanning system remarkably reduces total dissolved solids (TDS), biological oxygen demand (BOD), chemical oxygen demand (COD), and overall water load by 68.4%, 25.4%, 59.5%, and 33.7%, respectively, heralding a promising era of water and environmental sustainability in the leather sector. This study holds the potential to transform leather production, wherein the envisioned future on the use of the Taguchi model and optimized MaSil tanning system could find a place in shaping a cleaner, greener, and more sustainable leather industry.

Tuning a green carboxymethyl cellulose-based pre-tanning agent via peroxide oxidation for high chrome exhaustion in leather industry.

The low chrome uptake by collagen in the conventional tanning process leads to the pollution of the wastewater. Due to environmental concerns, leather scientists are already searching for innovative ways to produce pre-tanning agents as a high exhaustion chrome tanning auxiliary. Herein, a novel kind of pre-tanning agent is engineered by converting carboxymethyl cellulose (CMC) to oxidized carboxymethyl cellulose (OCMC) via the hydrogen peroxide process. FT-IR and carboxyl content analysis demonstrated the increase in carboxyl content after oxidation. After that, the obtained OCMC was utilized as a pre-tanning agent, resulting in a high exhaustion of chrome (92.76 %) which is 27.76 % more than conventional chrome tanning (65 %), and the amount of chrome in wastewater reduced to 7.24 %. The hydrothermal stability of wet-blue increased by increasing the uptake of chrome (Ts = 118 °C). The obtained crust leather represented excellent mechanical properties (Tensile strength: 305.68 kg/cm2; tear strength: 50 kg/cm) and desirable organoleptic properties. The environmental analysis signifies a significant step towards a cleaner and sustainable tanning process (COD = 1600, BOD5 = 560 mg/L) compared to the conventional chrome tanning process. Consequently, the obtained results offer a green pre-tanning agent to meet the requirements of the sustainable development of 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.

New materials-based on gelatin coordinated with zirconium or aluminum for ecological retanning.

Ecological retanning agent is an effective way to solve the pollution source of leather manufacturing industry. In this study, the gelatin from chrome-containing leather shavings in the leather industry was used to realize sustainable leather post-tanning. The gelatin hydrolysate (GH) coordinated with Zr4+ or Al3+ to prepare eco-friendly retanning agents GH-Zr and GH-Al. The successful coordination between GH and metal ions was characterized by FTIR and XPS. The retanning agents were characterized by FTIR curve-fitting and circular dichroism spectroscopy. The results showed that the conformation of the secondary structure of the polypeptide became ordered and stable after coordinating with the metal ions. The particle size and weight average molecular weight of the retanning agents were ~1700 nm and ~2100, respectively, measured by nanoparticle size analyzer and gel permeation chromatography (GPC). The retanning agents were applied to retanning of chrome tanned leather and glutaraldehyde tanned leather. The abundant free amino from retanning agents can consume the free formaldehyde. Meanwhile, retanning agents can effectively improve the multiple binding sites, resulting in favorable thickening rate (>110 %) and excellent dye and fatliquor absorption rate with ~99.91 % and ~93.18 %. Thus, this strategy can provide a viable choice for solid leather waste and sustainable development of the leather industry.

Bioprocess to valorise fleshing produced in the tanning industry.

This study focuses on circular bioeconomy and how to reduce the management of solid by-products in tannery facilities. To achieve this, double enzymatic hydrolysis has been developed, which allows the integrated management of both limed and fresh fleshing that are classified as category 3 animal by-products (ABPs). Fleshing has an average content of 15% fat, 20% protein and 65% water. To process these components independently, the fat fraction is separated from the protein and liquid protein fractions. This bioprocess has been developed from fleshing, yielding up to 78% mass recovery as biostimulants that are suitable for formulation and use in the fertiliser market. The efficacy of the protein fraction as a biostimulant was validated through laboratory tests, specifically by cabbage germination, which exhibited a notable improvement by 25%.

NaH2PO4 synergizes with organic matter to stabilize chromium in tannery sludge.

Heavy metal stabilization is an effective method to treat chromium in tannery sludge. Here we show that mainly investigated NaH2PO4 (MSP) and organic matter (OM) to stabilize chromium in tannery sludge. The experimental investigation revealed that the addition of montmorillonite (MMT) and MSP samples showed a significant increase in the percentage of reducible and oxidizable Cr in the former compared to the samples with the addition of MMT. This is attributed to the formation of Cr-O bond, which allows the MSP to undergo an inner-sphere complexation reaction with the metal oxide of Cr via ligand exchange. Significantly, the MSP moiety adsorbs on the surface of OM through monodentate, which increases the adsorption sites of OM for Cr6+ and promotes the reduction of Cr6+ to Cr3+. Moreover, PO43- reacts with Cr3+ to produce CrPO4 precipitation, thus reducing the free Cr3+ content. Finally, DFT calculations confirmed that a ternary system is formed between PO43-, OM, and Cr, and the binding energy is negative, which indicated that PO43- could co-stabilize Cr with OM.

Synthesis and crosslinking of collagen using 4-3,4,5-tris(oxiran-2-ylmethoxy)benzamido)benzenesulfonic acid for the development of robust metal-free leather.

The leather manufacturing sector is actively pursuing organic alternatives to replace the utilization of inorganic tanning chemicals such as chromium, zirconium, and aluminum due to concerns over their environmental impact. Although glutaraldehyde has been considered a feasible alternative, it still falls short in providing the leather with greater tensile properties and is also considered to be toxic. In this study, we report the synthesis of a sulfonated gallic acid-based epoxide (GSE) and evaluate its performance as a metal-free tanning compound. The synthesized compound was subjected to comprehensive characterization using FTIR (functional group), ESI-MS (molecular weight), and NMR (chemical environment) spectroscopy. Furthermore, the leather treated with GSE demonstrated organoleptic and physical properties that were comparable to those achieved with glutaraldehyde tanning systems. SEM analysis of the GSE-tanned leather exhibited a homogeneous distribution pattern, confirming the stability of the collagen. In addition, the hydrothermal stability temperature of leather crosslinked with epoxide was found to be 83 ± 2 °C. The wastewater generated from the GSE tanning process exhibited a BOD to COD ratio of 0.35 ± 0.04, indicating its high treatability. The results showed that the GSE tanning system provided better tanning efficiency and improved crosslinking and thermal stability without the use of metal salts. Furthermore, the use of GSE as a tanning agent offers several advantages, such as easy availability, biodegradability, and low toxicity, making it a sustainable and environment-friendly option for the leather industry.

A continuous process in mixers-settlers for the removal/recovery of chromium in effluents from the tanning industry.

One of the main environmental issues caused by the tanning industry is given by the high concentration of chromium contained on its effluents. The removal of this pollutant has become a technological challenge. To solve this issue, this work proposes a continuous process based on mixers-settlers for the removal of the chromium present in effluents from the tanning industry. The process involves the use of liquid-liquid extraction systems. The study includes the development of isotherms for the removal and stripping, which are further represented through a mathematical model to determine the number of theoretical extraction stages and other operational variables. The results show that a better extraction is achieved in a system with two theoretical stages using Cyanex 272 as extractant, reaching more than 94% of removal of chromium with an extractant concentration of 0.32 mol/L. For stripping, sulfuric acid is used, obtaining a maximum recovery of 94%.

Potential of biofuel production from leather solid wastes: Indian scenario.

India is one among the major leather-producing countries in the world which shares close to one-fourth of the world's leather solid wastes and most of these wastes are not effectively utilized. These wastes are rich in protein and lipids that could be a potential feedstock for biofuel production, i.e., biogas, biodiesel, etc. Among the 150,000 tons of daily leather solid wastes in India, approximately 87,150 tons are shared by pre-tanning operations (i.e., raw trimmings, fleshing, and hair wastes) while the rest of the 62,850 tons are shared by tanning, post-tanning, and finishing operations (i.e., wet blue trimmings, chrome splits, shavings, buffing dust, crust trimming wastes). This review article shows that there is considerable bioenergy potential for the use of leather solid wastes as a green fuel. The biogas potential of leather solid wastes is estimated to be 40,532.9 m3/day whereas the biodiesel potential is estimated as 15,452.6 L/day. The bio-oil and bio-char potential of leather solid wastes is estimated to be 80,513.0 L/day and 45.8 tons/day, respectively. Several factors influence the biofuel process efficacy, which needs to be taken into consideration while setting up a biofuel recovery plant. The overall biofuel potential of leather solid wastes shows that this feedstock is an untapped resource for energy recovery to add commercial benefits to India's energy supply. Furthermore, in addition to the economic benefits for investors, the use of leather solid wastes for biofuel production will yield a positive environmental impact.

A cleaner leather chemical from feather waste for reducing ammonia-nitrogen pollution and improving biological treatment efficiency of tannery wastewater.

Feather waste is produced in millions of tons globally every year, resulting in a waste of biomass resources and even environmental pollution. A sustainable strategy for utilizing feather waste was proposed by preparing a clean deliming agent for ammonia-nitrogen (NH3-N) reduction in leather manufacture and biological treatment efficiency improvement of tannery wastewater. Briefly, chicken feather wastes were deeply hydrolyzed with sulfuric acid, and the optimized keratin hydrolysate (KHopt) that contained 53.6% crude protein and 41.2% amino acids, such as glutamic acid, serine, proline, leucine, phenylalanine, glycine, valine, and arginine, was obtained and used to delime limed cattle hides. The appropriate ratio of amino acids in KHopt gave KHopt a great pH-buffering capacity and maintained a stable float pH of approximately 9 throughout the deliming process. The isoelectric points of KHopt (3.8) and the limed hide (6.3) were both lower than the float pH, thereby bringing about an electrostatic repulsion between the KHopt and the hide surface, which is helpful for KHopt to penetrate and deswell the limed hide rapidly. Moreover, the KHopt deliming effectively removed calcium from the limed hide and achieved leather comparable to conventional leather for commercial applications. KHopt reduced the NH3-N concentrations of deliming effluent and tannery wastewater by 91.1% and 80.6%, respectively, compared with the conventional deliming agent (ammonium sulfate), and dramatically increased the biological treatment efficiency of tannery wastewater. The results showed that efficient and high-value use of feather waste was made by preparing KHopt for sustainable leather manufacturing.

Unexpected associations of long-term and excessive exposure to trivalent chromium with hypertension and glycosuria in male tannery workers.

Serious health hazards including renal, skin and hearing disorders have been reported in Bangladeshi tannery workers (TWs) who were chronically exposed to a large amount of trivalent chromium [Cr(III)]. However, the effects of Cr(III) exposure on the prevalence of hypertension and the prevalence of glycosuria in TWs remain unknown. Since the Cr level in toenails is an established marker reflecting long-term exposure to Cr(III) in humans, the associations of Cr levels in toenails with the prevalence of hypertension and the prevalence of glycosuria in male tannery and non-tannery office workers (non-TWs) in Bangladesh were investigated in this study. The mean toenail Cr level in non-TWs (0.5 µg/g, n = 49) was comparable to that in the general population reported previously. Mean Cr levels in TWs with a low toenail Cr level (5.7 µg/g, n = 39) and those with a high toenail Cr level (298.8 µg/g, n = 61) were >10-fold and >500-fold higher, respectively, than that in non-TWs. Our univariate and multivariate analyses indicated that the prevalence of hypertension and the prevalence of glycosuria in TWs with a high toenail Cr level, but not in TWs with a low toenail Cr level, were significantly lower than those in non-TWs. This study showed for the first time that long-term and excessive exposure to Cr(III) that is more than >500-fold but not >10-fold higher than the usual exposure level could decrease the prevalence of hypertension and the prevalence of glycosuria in TWs. Thus, this study revealed unexpected effects of exposure to Cr(III) on health.

Degradation of tannery hide raw trimming hairs using keratinolytic bacteria isolated from tannery effluent-contaminated soil.

The disposal of keratinous wastes produced by several leather industries is evolving into a global problem. Around 1 billion tonnes of keratin waste are released into the environment each year. In the breakdown of tannery waste, certain enzymes, such as keratinases produced from microorganisms, might be a better substitute for synthetic enzymes. Keratinase enzymes are able to hydrolyze gelatin, casein, bovine serum albumin and insoluble protein present in wool, feather. Therefore, in this study, bacterial strains from tannery effluent-contaminated soil and bovine tannery hide were isolated and assessed for their ability to produce the keratinolytic enzyme. Among the six isolates, the strain NS1P showed the highest keratinase activity (298 U/ml) and was identified as Comamonas testosterone through biochemical and molecular characterization. Several bioprocess parameters such as pH, temperature, inoculum size, carbon sources, and nitrogen sources were optimized in order to maximize crude enzyme production. The optimized media were used for inoculum preparation and subsequent biodegradation of hide hairs. The degradation efficacy of the keratinase enzyme produced by Comamonas testosterone was examined by degrading bovine tannery hide hairs, and it was found to be 73.6% after 30 days. The morphology of the deteriorated hair was examined using a field emission scanning electron microscope (FE-SEM), which revealed significant degradation. Thus, our research work has led to the conclusion that Comamonas testosterone may be a promising keratinolytic strain for the biodegradation of tannery bovine hide hair waste and the industrial production of keratinases.

Facile degradation of chitosan-sodium alginate-chromium (III) gel in relation to leather re-tanning and filling.

Natural polysaccharide hydrogel, exemplified by chitosan­sodium alginate (CS-SA), has been prevailing in adsorption of chromium (III) (Cr(III)) containing contaminant. However, the traditional desorption of CS-SA-Cr(III) to recycle the adsorbent faces the problems including chemical desorbents secondary pollution, resource waste of the terminal CS-SA adsorbents, and tedious work of reusing the desorbed Cr(III). Herein, the adsorption product, CS-SA-Cr(III) gel, was degraded to CS/SA/Cr(III) sol and applied in leather re-tanning and filling processes directly. To achieve this goal, three degradation methods were used to transform the gel to sol. Due to the excellent overall performance of the CS/SA/Cr(III)-HMD4 sol (obtained by the hydrothermal-mechanical degradation method for 4 h (HMD4)), including wide size and distribution range, moderate viscosity (54 ± 3.1 mPa·s), high electronegativity (-38.6 ± 5.8 mV), and good stability, the resultant leather after re-tanning and filling by the sol achieved fascinating properties such as good thermal stability (Ts, 116.8 ± 1.8 °C; Td, 94.2 ± 1.7 °C), mechanical performance (tensile strength, 6.9 ± 0.52 MPa; elongation at break, 95 ± 3.0 %), and superduper thickening rate (31.8 %). Moreover, the mechanism of good re-tanning and filling effects was deciphered. Therefore, this work intends to overcome the limitation of traditional desorption technology and further realizes the high-valued application of the exhausted CS-SA-Cr(III) in leather re-tanning and filling processes.

Preparation and application of tremella polysaccharide based chrome free tanning agent for sheepskin processing.

The abuse of chrome tanning agent in leather processing has caused great harm to human health and the natural environment. We use tremella polysaccharides (TP), lentinan (LNT) and konjac gum (KG) as raw materials, and sodium periodate as oxidant to prepare the corresponding polysaccharide tanning agent. Tremella polysaccharide was selected as the best tanning agent according to the shrinkage temperature, and the subsequent experiments were carried out. Tremella polysaccharide (TP) as raw material and sodium periodate as an oxidant, dialdehyde tremella polysaccharide (DTP) was prepared and applied in leather tanning. The effects of different oxidation conditions (sodium periodate dosage, temperature, pH, and reaction time) on the shrinkage temperature of DTP tanned leather were studied. The change of shrinkage temperature showed that the dosage of sodium periodate had the greatest influence on the shrinkage temperature. Therefore, the effects of different dosage of sodium periodate on the aldehyde content and molecular weight of DTP were investigated, including the analysis of physical properties and microstructure of tanned leather. In general, the increase of sodium periodate dosage was found to increase the aldehyde content and reduce the molecular weight, which was more conducive to leather tanning.

Analysis of heavy metals and toxicity level in the tannery effluent and the environs.

Heavy metals have found a large number of applications in the recent times. These heavy metals are being continuously added to our environment through various natural and anthropogenic activities. Industries employ heavy metals to process raw materials into final products. Effluents from these industries carry heavy metals. Atomic absorption spectrophotometer and ICP-MS (inductively coupled plasma-mass spectrometer) are of great help in detecting various elements in the effluent. They have been extensively applied to solve problems related to environmental monitoring and assessment. Heavy metals like Cu, Cd, Ni, Pb, and Cr can be easily detected using both the techniques. Some of these heavy metals are toxic to both humans and animals. They can have significant related health effects. Presence of heavy metals in the industrial effluent has gained varied attention in the recent times and it has become one of the major causes of water and soil pollution. Significant contributions can be linked with the leather tanning industry. As the effluent from the tanning industry has been found to contain a large number of heavy metals in many studies. Continuous monitoring and treatment of the effluent is necessary to keep a check on the concentration of heavy metals in these effluents. This study focuses on the analysis of the various studies available on tannery effluents, methods used for heavy metal analysis, toxicity of these heavy metals, and the related major health effects. Data for heavy metals in the tannery effluent from different studies in last two decades has been collected and analysed. The data from various studies indicates that Cr, Cd, Pb, Zn, Cu, Fe, and Ni are the most commonly found heavy metals released from the tanning industry. Proper management of the tannery effluent is thus very essential for saving the environment.