Mariliz Gutterres

Hide unhairing and characterization of commercial enzymes used in leather manufacture

Abstract - The enzymatic treatment of hides in tannery processes is a promising technology. However, the reaction kinetics of commercial enzymes available to the leather industry are not fully understood and their activities have been mainly determined with model proteins such as casein as substrate, which are not of direct relevance for cattle hides. Therefore, it is important to determine their activities on collagen and keratin, the main proteins of skin, in order to use these enzymes in leather processing. This work describes the study of five proteases, used commercially in tanneries, to assess their ability to act upon collagen and keratin and to determine their unhairing. Results showed that all commercial enzymes tested had more activity on collagen than on keratin. Unhairing was also tested and four out of the five enzymes tested showed some unhairing activity. Optima of the temperature and pH of the enzymes were very similar for all five enzymes, with maximal activities around 55°C and pH 9 to 12, respectively.

Production of basic chromium sulfate by using recovered chromium from ashes of thermally treated leather

Leather wastes tanned with chromium are generated during the production process of leather, hence the wastes from hand crafted goods and footwear industries are a serious environmental problem. The thermal treatment of leather wastes can be one of the treatment options because the wastes are rich in chromium and can be used as a raw material for sodium chromate production and further to obtain several chromium compounds. The objective of this study was to utilize the chromium from leather wastes via basic chromium sulfate production to be subsequently applied in a hide tanning. The obtained results have shown that this is the first successful attempt to achieve desired base properties of the product. The result was achieved when the following conditions were applied: a molar ratio between sodium sulfite and sodium dichromate equal to 6; reaction time equal to 5 min before addition of sulfuric acid; pH of sodium dichromate solution equal to 2. Summarizing, there is an opportunity to utilize the dangerous wastes and reused them in the production scheme by minimizing or annulling the environmental impact and to attend a sustainable process development concept.

The influence of Chromium supplied by tanning and wet finishing processes on the formation of cr(vi) in leather

Chromium used in leather manufacturing can be oxidized from the trivalent to the hexavalent state, causing environmental concerns. In this study, the influence of Cr(III) from tanning, deacidification pH, fatliquors, chrome retanning and vegetable retanning on the formation of Cr(VI) in leather was analyzed by comparing natural and aged samples. In wet-blue leather, even after aging and in fatliquored leathers that did not suffer the aging process, the presence of Cr(VI) was always below the detection limit of 3 mg/kg. Considering the presence of Cr(VI), the supply of chromium during the retanning step had a more significant effect than during the tanning. In the fatliquoring process with sulfites, fish and synthetic fatliquor leather samples contained Cr(VI) when aged, and the highest concentration detected was 26.7 mg/kg. The evaluation of Cr(VI) formation led to recommendations for regulation in the leather industry.

Wastewater Reuse Focused on Industrial Applications

Water scarcity is a pressing problem around the world. Many countries will be experiencing severe water shortages over the next decades, and this has become an issue for both the public and private sectors. The quality required for wastewater discharge should take into consideration concerns about public health and safe use. Wastewater reuse, including recycling, is an important component of both wastewater and water resource management. There are many wastewater reuse applications that do not require drinking water quality. The types of wastewater reuse are classified in four main categories: urban uses, industrial uses, agricultural uses and groundwater recharge. According to the pollutant components, the wastewater treatment technology, and the water quality obtained, the wastewater reuse type and system are selected observing the potential constraints due to the levels of remaining residual charge. Water is provided by water companies as a service and has many other industrial purposes. The suitability of reclaimed wastewater in industry depends on the process and on the particular purpose, and different purification grades may be required. Types of wastewater reuse, characterization of water contaminants, guidelines for wastewater reuse, industrial usage, water and wastewater management, treatment technologies, mass integration and industrial reuse cases are discussed in this chapter.

CHAPTER 16:Chromium in Tannery Wastewater

Chromium is found naturally in the environment in rocks, animals, plants, soil, volcanic dust and mists. Chromium is not found free in the most important deposits of the planet, it is found in elemental form or in the trivalent oxidation state. The conversion from trivalent to hexavalent oxidation state of chromium is an important feature, where hexavalent chromium predominates under highly oxidizing conditions. The majority of the chromium in the surface water may be in the form of particulate matter or deposited sediment. Industrial effluents containing chromium are discharged into rivers, soil and air. The results of several studies point to the need to control wastewater, considering that the improper disposal of chromium contributes to contamination of water resources and groundwater. The main human activities in which the chromium and its compounds are released into the environment result from the manufacture of cement and construction materials, welding alloys, foundries, manufacturing steel and alloys, electroplating industry, lamps, mines, urban waste and industrial waste incineration, coal ash, tanneries, fertilizers and wood preservatives. Solid wastes and wastewaters from leather manufacturing contain chromium. The use of chrome in the tanning process occurs with the trivalent chromium, usually in the form of basic chromium sulfate. The effects of chromium in the environment, water contamination by chromium, the process management and technologies of chromium usage in tanneries, the wastewater treatment operations and the chromium recovery will be addressed in this chapter.

Treatment of Leather Dyeing Wastewater with Associated Process of Coagulation-Flocculation/Adsorption/Ozonation

ABSTRACT This study is based on the investigation of performance of associated wastewater treatments of coagulation-flocculation/adsorption (CF-ADS) and coagulation-flocculation/ozonation (CF-OZ) for the removal of pollutants from tannery wastewater. The chemical dosage was optimized and the use of waste from the tannery process was tested as a low-cost alternative adsorbent for wastewater treatment plants. For the CF-ADS the removal of TOC, COD, Na+ and color were 50.04%, 53.13%, 17.05% and 61.13%, respectively, and for the CF-OZ the removal were 46.50%, 56.25%, 11.10% and 85.34%. Also, BOD/COD and COD/TOC ratios were studied to verify the oxidation efficiency of the wastewater.

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

Tanneries are industries that may cause high environmental impact. Consequently, they are responsible for generating a large amount of wastewater with high concentrations of contaminants that require significant investment and operating costs in their treatment in order to accomplish the emission standards required by environmental legislation. This work has as main objective to minimize the environmental impact of the water used by tanneries through the study of reuse possibilities of wastewater tanning floats. The major concern is related to the pollutant chromium in the environment, since it is the tanning product that gives the best characteristics to leather and consequently the most used product. The reuse tests were performed on pilot and industrial scales. During the experiments, the following process control parameters were evaluated: pH, density, acid-base indicators for hide and shrinkage temperature. To validate the water reuse in tanneries, samples of wet-blue leather and residual floats were collected from pilot and industrial processes to perform chemical analyses to prove the validity of the process with reuse. Research has shown that reuse techniques, when properly evaluated, can be used in industries. In addition to reducing water demand, the reuse of wastewater in tanning processes minimizes the disposal of the wastewater with chromium and uses the residual chromium float.

Hybrid sol–gel silica adsorbent materials synthesized by molecular imprinting for tannin removal

This study reports the development of a functional adsorbent synthesized by the molecular imprinting method in a sol–gel matrix. The adsorption capacity of the organic-inorganic hybrid adsorbent material was tested on tannin compounds, i.e., phenolic substances that are among the most difficult compounds to remove in industrial wastewater. The specific surface area obtained by nitrogen porosimetry analysis was between 2 and 579 m2 g−1 due to each sol–gel synthetic route used. Small-angle X-ray scattering analysis revealed that the hybrid silicas were arranged in a multi-level structure consisting of three levels of organization and a surface fractal structure. Diffuse reflectance spectroscopy revealed the interactions between the tannins and the silica matrix, and confirmed the partial removal of tannins after ultrasound-assisted extraction. Zeta potential analysis showed that the values ranged between −37.9 and +27.8 mV, where non-functionalized xerogels were anionic and those functionalized with organosilane were cationic. The structural and textural characteristics of the hybrid materials were found to depend on the sol–gel synthetic route, which in turn affected the adsorption capacity. The adsorbent functionalized with (3-Aminopropyl) triethoxysilane was an effective adsorbent for the tannin compounds tested here, with approximately 90% removal in aqueous solutions.Graphical abstract

Estudo de um consórcio de microalgas na remoção de nutrientes de efluentes de curtume

A microalgas se multiplicam rapidamente em aguas ricas em nutrientes ou eutrofizadas, principalmente com altas cargas de fosforo e nitrogenio. Algumas pesquisas tem buscado por especies capazes de crescer em efluentes industriais explorando as vantagens das microalgas em remover os nutrientes dos efluentes e gerar biomassa com valores agregados. O presente trabalho teve como o objetivo testar um consorcio de microalga no tratamento de efluente de curtume. Foi acompanhado o crescimento das microalgas no efluente e a remocao de nutrientes associada a este processo. O consorcio se mostrou eficiente acarretando remocoes de Nitrogenio e Fosforo de 88,61% e 92,58%, respectivamente e foi possivel isolar uma cultura unialgal do microrganismo mais representativo.