Valorization of agitated thin film dryer (ATFD)-mixed-salt from textile wastewater for its application in leather manufacturing - a sustainable approach

The textile industry uses sodium chloride and sodium sulphate during the dyeing process to improve the fixation of dyes on fabrics. After wastewater treatment, the reject stream is dried resulting in mixed salts as solid wastes that are not reused. The leather industry also uses a vast quantity of salt for temporary preservation of skins/hides and as swelling-suppressing agent during the pickling (acidification) process. Thus, an attempt was made to utilize the mixed salt obtained from the textile industry to replace sodium chloride in leather processing. It was found that a 40% w/w offer of ATFD salt was able to preserve the skins for 3 months, which was on par with the preservation carried out using a similar quantity of sodium chloride in conventional preservation process. Likewise, for the pickling process, an offer of 10% w/w ATFD salt provided sufficient deswelling action when compared to conventionally used sodium chloride. However, the residual colour of the mixed salts affected the quality of the leather obtained. To overcome this, an electro-oxidation treatment was carried out to obtain decolourized salts. The COD measurements showed that the 1% solution of ATFD-3 salt reduced from 471 ± 25 to 88 ± 16 ppm. A similar trend was also seen in BOD reduction from 80 ± 12 to 18 ± 10 ppm. These results confirmed that the colour removal could be due to the degradation of the organic contaminants present in the ATFD salt. Thus, the treated ATFD salt can be reused for leather processing without affecting leather quality, thus promoting the concept of circular economy.

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.

Anti-diabetic and hypolipidemic effects of Cinnamon cassia bark extracts: an in vitro, in vivo, and in silico approach

The present investigation was aimed to study the anti-diabetic and hypolipidemic potential of Cinnamon cassia (Lauraceae family) bark in streptozotocin (STZ)-induced diabetic rats. The preliminary phytochemical analysis (hexane, petroleum ether, chloroform, ethanol, methanol, and aqueous extracts), GC-MS analysis (ethanol), in vitro (aqueous, ethanol and methanol), in vivo (ethanol) and in silico anti-diabetic activity with hypolipidemic effect of C. cassia bark was analysed. The ethanolic extract of the C. cassia bark has a fine inhibitory activity than the aqueous and methanolic extract. Out of 20 different compounds identified, seven compounds were biologically active, and 9-octadecenoic acid has highly interacted with PPARα/γ in docking studies. The levels of diabetic markers, enzymes, and lipid profiles were altered in STZ-induced rats, but after the treatment of C. cassia, the levels were returned to the normal. The study may prove the ethanolic extract of C. cassia has a powerful anti-diabetic and anti-hyperlipidemic activity.

Compact glyoxal tanning system: a chrome-free sustainable and green approach towards tanning-cum-upgradation of low-grade raw materials in leather processing

Increased concern over the use of metal salts such as chromium, zirconium, and aluminum for tanning of hides and skins has made the leather production industry to be constantly on the lookout for organic tanning agents in place of the inorganic system. Though glutaraldehyde has been looked at as a viable option, it still lags in imparting superior strength properties to the leather and also it has been reported to have inherent toxicity. With that concept in view, this research work focuses on the usage of glyoxal along with synthetic tanning agents as a replacement for glutaraldehyde and other inorganic tanning systems. The offer level and starting pH for the glyoxal tanning process was optimized as 6% (w/w) and 5.0, respectively, and the shrinkage temperature of the collagen was found to be around 80 °C. Additionally, the controlled shrunken grain effect of the aldehyde tanning system was explored by changing the pH of the process, which helped to improve the thickness of low-grade thinner raw materials by up to 40%. The mechanism for the shrunken grain effect has also been proposed in this work by studying the dimensional changes occurring in the leather matrix upon treating skin/hide with glyoxal at different pH levels. The mechanical and strength properties of the leather were found to be better than the glutaraldehyde tanning system. The BOD/COD ratio of wastewater generated from the glyoxal process was found to be greater than 0.3 making them easily treatable. Considering all these factors, compact glyoxal-based tanning along with synthetic tanning agents can be a game-changing technology for the leather processing industry.

Non-aqueous green solvents improve alpha-amylase induced fiber opening in leather processing

Severe water deficit and highly polluting effluent generation from leather industries have constantly been pressurizing the tanners to adopt cleaner leather processing systems. The present study aims to minimize the use of water by substituting it with non-aqueous green solvents and also to enhance the enzyme action in alpha-amylase based fiber opening process. The activity of alpha-amylase in select non-aqueous green solvents namely, heptane, polyethylene glycol 200 and propylene glycol is considerably higher by 62, 38 and 31% than in water, respectively. Comparable results are obtained for the catalytic efficiency of alpha-amylase and hence it is further validated in collagen fiber opening trials as well. Scanning electron micrographs, histological images and proteoglycan estimation supported the above findings at 1% alpha-amylase dosage. The final quality of the experimental leathers in terms of physical and bulk properties is comparable to that of control leathers. Recycling studies indicate that it is possible to replace water with green solvents for enzymatic fiber opening with the feasibility to recover more than 85% solvent-enzyme mixture and reuse without any additional alpha-amylase usage. Reduction in pollution load coupled with the efficient catalytic action of enzyme in non-aqueous media favors the present protocol for industrial applications.

Biosorption of bovine serum albumin by Ulva lactuca biomass from industrial wastewater: equilibrium, kinetic and thermodynamic study

Batch biosorption experiments have been carried out for the removal of bovine serum albumin (BSA) from simulated industrial wastewater onto Ulva lactuca seaweed. Various vital parameters influencing the biosorption process such as initial concentration of BSA, pH of the solution, adsorbent dosage and temperature have been determined. The biosorption kinetics follows a pseudo-second order kinetic model. Equilibrium isotherm studies demonstrate that the biosorption followed the Freundlich isotherm model, which implies a heterogeneous sorption phenomenon. Various thermodynamic parameters such as changes in enthalpy, free energy and entropy have been calculated. The positive value of ΔH° and the negative value of ΔG° show that the sorption process is endothermic and spontaneous. The positive value of change in entropy ΔS° shows increased randomness at the solid-liquid interface during the biosorption of BSA onto U. lactuca seaweed.

Biosorption of cadmium metal ion from simulated wastewaters using Hypnea valentiae biomass: a kinetic and thermodynamic study

Present study deals with the evaluation of biosorptive removal of cadmium by red macro alga Hypnea valentiae. Experiments have been carried out to find the effect of various parameters such as initial cadmium concentration, experimental pH and temperature on the biosorption potential of H. valentiae. Optimum pH for biosorption of cadmium was found to be 6+/-0.3. A maximum removal of about 17mg of cadmium per g of micro algae was observed at pH 6.0 for 250mgL(-1) solution of cadmium. Kinetics of cadmium biosorption by H. valentiae biomass is better described by pseudo first order kinetic model. The equilibrium isotherm data are very well represented by Langmuir isotherm equation, which confirmed the monolayer coverage of cadmium onto H. valentiae biomass. Various thermodynamic parameters such as change in enthalpy, free energy and entropy were estimated. It was also clearly observed that the presence of neutral salts and other metal ions affected the cadmium uptake behavior of the biomass considerably.