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Wastewater Treatment, Recycling and Reuse
Published in P.K. Tewari, Advanced Water Technologies, 2020
In tanneries, animal hides are treated with inorganic and organic chemicals at different stages from storage and conservation through to dyeing and finishing. A lot of water is used and at the end of the process, water carries some chemicals as contaminants and pollutants. One of the chemicals widely used in the tannery industry is chromium sulfate, because it has a high penetration rate into the fibrillar interspaces of the skin and gives hides good mechanical and hydrothermal resistance and exceptional suitability for dyeing. As it is used to excess, about 30–40% of initial chromium is found in the wastewater and sludge of the biological waste treatment plant and tanned skin residues. Recovery of chromium from the tanning bath makes economic sense. Once the chromium has been recovered, the biological sludge and hide residues can easily be reused in agriculture. A process flow diagram for recovery of chromium solution from the tanning process is shown in Figure 7.4.
Im pregnation of Iron and Magnetite Phases in Wood and Partial Pyrolized Wood
Published in Omari V. Mukbaniani, Tamara N. Tatrishvili, Marc J. M. Abadie, Science and Technology of Polymers and Advanced Materials, 2019
K. Sarajishvili, N. Jalabadze, L. Nadaraia, G. Kvartskhava, T. Korkia, N. Nonikashvili, V. Gabunia, R. Chedia
The content of inorganic and organic pollutants in the environment depends on different types of production and the quality of the water pollution. Therefore, in each case, appropriate sorbents and purification technologies must be adopted. It is possible to remove inorganic and organic pollutants from wastewaters separately or simultaneously through mono- and multi-functional sorbents, which will be hybrid systems containing organic-inorganic or inorganic components. It is well known that biosorbents obtained from renewable bio-resources can remove ions of heavy metals from polluted water [9–21]. Biosorbents obtained by us from wastes of oak (Quercus), hornbeam (Carpinus), poplar (Populus italic, populous pyramidalis), plane tree (Platanus) and beech (Fagus) wood processing) have been tested for removing of Crions from waters [22–24]. Removal of chromium from wastewaters of the tannery is a topical challenge: chromium sulfate (basic) is used in the leather production technology of Georgian tanneries. Only 60–70% of chromium is used in leather, all the rest appear in the wastewaters. From the local inorganic mineral resources, it is possible to use aluminosilicates (zeolite tuffs, clays, etc.); renewed bioresources often are used as heavy metal adsorbents, but they have less degradation ability for organic pollutants. For assigning of multi-functional properties to natural biosorbents, the necessary components should be added, which will increase their ability to absorb heavy metal ions and degraded organic pollutants. It is necessary to impregnate nZVI or iron-containing compounds (oxides, hydroxides) into biosorbents and as a result, inorganic-organic sorbents will be created. Mild chemical modification of biosorbents (including partial pyrolysis of wood) is also necessary with the aim of making lining inert towards active component-nanoiron and to avoid its deactivation. This article applies to the development of methods for impregnation of ultradispersed powders of iron and magnetite into the wood and partially pyrolyzed wood.
Extraction of chromium from tannery sewage sludge
Published in Canadian Metallurgical Quarterly, 2022
Bin Hu, Changda Zhang, Huaguang Wang, Guiqing Zhang, Qinggang Li, Mingyu Wang
The chromium in raw tannery sewage sludge mainly exists in the form of hydrated chromium oxide, and the rest of chromium is combined with the carboxyl group of collagen to form a complex organic material [21], which has strong hydrophobicity. The tannery sewage sludge can float on the surface of the acid solution, which leads to the difficulty of using the process of direct acid leaching. However, the technology of sulfuric acid curing followed by water leaching can solve this problem effectively. In the process of sulfuric acid curing, the acidity and the dehydration of 98% sulfuric were used at the same time. After sulfuric acid curing, the organic matter in tannery sewage sludge is dewatered and carbonised, thus avoiding the floating of materials in the subsequent water leaching process. At the same time, the chromium compound in raw tannery sewage sludge also reacts with sulfuric acid to form soluble chromium sulfate.
Heavy metals in municipal waste: the content and leaching ability by waste fraction
Published in Journal of Environmental Science and Health, Part A, 2019
In municipal waste, most chromium is derived from spent batteries (lithium-silver chromate electrolyte in lithium batteries), waste paints, and varnishes. High chromium content was found in the printed circuit boards of mobile phones (average concentration 9.9 g kg−1) [17, 18], while being low in other e-waste. Chromium oxides are used in dyes and some pesticide groups. Chromium sulfate is used in leather products as a tanning agent. Potassium and sodium dichromates are added to antiseptics used to cover and protect various products. In comparison to previous metals, there are more chromium compounds soluble in water (chromium sulfate, potassium, and sodium dichromates). Therefore, chromium compounds may be disseminated in the environment more easily than for other metals.