A Review of Eco-Friendly Preservative and Bio-Tannin Materials Using Powdered Barks of Local Plants for the Processing of Goatskin

Skin is a raw material which is considered as the heart of leather making process. Skin falls vulnerable upon the flayed of the animals and is seriously invaded by bacteria if it is not well protected. Curing and preservation of raw stock resist putrefaction and reserve leather quality. Worldwide, most commonly used skin preservation is by using table salt which is accused of polluting the environment by increasing soil salinity, affecting water body, releasing more than 40% dissolved solids and 55% chlorides etc. Further, on the side of leather tanning, 80-90% of all leathers is manufactured by tanning with basic chromium (III) salt, because of its excellent features and is also solemnly accused that; its safety record is cautionary, uncontrolled emission of chromium (VI) and it is a limited natural resources. Pollution control authorities of many countries are imposed severe restrictions on both salt preservation and chrome tanning forcing the tanners and researchers to look for possible alternative ways that are naturally abundant, easily obtainable, low priced, eco-friendly and offer competitive with existing tanned leather performances. The critical reviewed was targeting the recent alternatives trends to skin/hides salt preservation as well as vegetable tanning as a possible way to replace the use of basic chromium salt for the sustainability of leather industry and to further suggest another preservative and vegetable plant to be used in future studies.

Phytoavailability of chromium in chromium salt and poultry feed

A pot-culture experiment was conducted to investigate phytoavailability of chromium in inorganic chromium salt and raw poultry feed made from tannery waste. Poultry feed from tannery waste was applied to the soil at a rate of 5 t/ha while inorganic chromium salt was applied at a rate of 10 mg/ kg and 810 mg/kg. An upland leafy-vegetable commonly known as Kalmi (Ipomoea aquatica) was used to assess the phytoavailability. Physico-chemical analyses of all soil and plant samples were done at 0, 15, 30 and 45 days of incubation to assess chromium phytoavailability and also its effects on the uptake of other heavy metals viz., lead and iron. Plants treated with Cr showed declined vegetative growth, low accumulation of dry matter, reduced nutrient concentration and reduced nutrient uptake. It was found that the plants accumulated higher amount of Cr from raw poultry feed treated soil compared to that of the inorganic Cr salt treated soil. The effect of treatments on Cr accumulation both in root and shoot was found significant. The study concludes that Cr is phytoavailable depending on the source and increased concentration of Cr decreases accumulation of Pb and Fe and thereby likely to decrease uptake of these metals. Dhaka Univ. J. Biol. Sci. 27(2): 201-211, 2018 (July)

Three-component coupling of aryl iodides, allenes, and aldehydes catalyzed by a Co/Cr-hybrid catalyst

The cobalt/chromium-catalyzed three-component coupling of aryl iodides, allenes, and aldehydes has been developed to afford multi-substituted homoallylic alcohols in a diastereoselective manner. Control experiments for understanding the reaction mechanism reveal that the cobalt catalyst is involved in the oxidative addition and carbometalation steps in the reaction, whereas the chromium salt generates highly nucleophilic allylchromium intermediates from allylcobalt species, without the loss of stereochemical information, to allow the addition to aldehydes.

Electrochemical treatment of spent tan bath solution for reuse

A spent tanning bath contains high concentration of salts, chromium and protein. The treatment system for removal of chlorides or chromium from this effluent is expensive. In this context this waste has to be reused. Our study focuses on the application of advanced oxidation processes for protein removal present in a tanning bath. To improve the quality of the chromium tanning bath, two electrochemical processes (electrooxidation and peroxi-electrocoagulation process, PEP) are investigated in a batch reactor. The effects of operational parameters such as reactor configuration, current density and electrolysis time on chemical oxygen demand (COD) and protein removal efficiency are examined. Results indicated that under the optimum operating range for process, the COD and protein removal efficiency reached 53 and 100%, respectively. The optimum values are determined for the hybrid process (PEP) under 0.13 A·cm−2 over 2 h. The treated tanning bath is used as a tanning solution in leather processing. The influence of chromium salt dose, pH solution, stirring time and contact time on the leather characteristic is evaluated. The hides tanned after the addition of 0.25% of commercial chromium salt, at pH solution, leaving them stirring for 4 h with a contact time of 2 days, and showed good hydrothermal stability and physical characteristics of leather.

Study on the Clean Production Process of Basic Chromium Sulphate

The pollution of chromium salt industry is increasingly serious in China and becomes a worldwide problem with the rapid development of chromium salt industry. Then a new clean production process with a high recovery rate of chromium and pollution-free was proposed according to the comprehensive summary of existing processes of basic chromium sulphate. Furthermore, a small amount of slag will be discharged in this short process with lower energy consuming. The design concept is also applicable to the preparation of other chromium salts products, which will eliminate the pollution of Cr6+ during the process of chromium salt production and be helpful to the comprehensive utilization of chromium salt. In addition, the guidance of scholar research and the broad application prospects of this work cannot be neglected.

Experimental Study on the Effective Separation of Chromium-Iron Ions in Multi-Component Solution System by Ihleite Method

As one of the raw material resources in China, chromium salt production has been paid to close attention. Alkali process of chromium salt produces serious environmental pollution, while acid production of chromium salt has separation problems of chromium-iron ions. The separation process of chromium-iron ions in acidic solution by the combination technology of hydrothermal method and ihleite method is studied in this paper. which finds that: with the increase of reaction temperature or with the extension of reaction time, precipitation rate of iron increases, while loss rate of chromium decreases.

A Maleinuric Acid / Acrylic Acid Copolymer with Functions of Softening Wet-Blue and Scavenging Free Formaldehyde in Leather

A low molecular weight copolymer suitable for retanning wet-blue in leather industry has been synthesized by copolymerizing maleinuric acid with acrylic acid. Its performances for improving physical properties of crust leather, fixing the free chromium salt existed in wet-blue and scavenging the free formaldehyde introduced by other chemicals were investigated by applying it on goatskin wet-blue. The results show that the strengths and extensions, especially the softness of the crust leather can be significantly improved by the copolymer. The chromium released from wet-blue during retanning and free formaldehyde in leather can be reduced by 84.9% and 70.4% respectively with an offer of 3% the copolymer. Soft leather with very low levels of chromium release and free formaldehyde could be obtained by retanning with this copolymer. Therefore, this copolymer has the good potential for industrial application in ecological leather.