This paper discusses the application of black CHROMIUM coating on steel substrates applicable in solar power plants obtained from the optimum electroplating black CHROMIUM bath. Black CHROMIUM is one type of selective coatings that used usually in solar power plants. As absorption and thermal radiation are related to black surface and undercoats respectively, the thickness of absorption layers should be lower than infrared wavelength so that undercoat shows its appropriate optical properties and decrease the thermal radiation. Since copper have lowest thermal radiation which is due to their high conductivity and also their smooth and polished surfaces, in this research copper selected as an undercoat. The result proves that Electrodeposition of copper on steel substrates from sulfate baths is possible. Electrodeposition was carried out at room temperature. The plating time and concentration was variable to find the best coat at minimum amount of copper sulfate. Then Electrodeposition of black CHROMIUM was also carried out at different time, temperature and composition of black CHROMIUM bath. Adjusting the pH level was not a matter of importance after bath preparations. Adhesion and Uniformity of the coatings were investigated by Scaning Electron Microscopy (SEM).

From the standpoint of processing, hard CHROMIUM layer plate may be applied to steels, cast iron, aluminum and nickel base alloys. Cast iron can be plated provided that the surface is capable of conducting the required current and is reasonably free of voids, pits, gross silicate inclusions, and massive segregation. There are many difficulties arising from graphite phase and deposition of hydrogen on the surface of gray cast iron (G.C.J). To obtain desired hard CHROMIUM coating with acceptable adhesion, special pretreatments should be used. In this paper the surfaces of G.C.I. were prepared in sulphuric acid, chromic acid + S04-- by anodic etching phosphoric acid + sulphuric acid solution by electro polishing and sulphuric acid + fluoridric solution by dipping in the different conditions. The best results for removal of graphite from the surface of specimens are obtained after anodic etching in 60% H2S04 solution.

Well-dispersed magnetite nanoparticles of different sizes between 15 and 43 nm were synthesized by an electrochemical method in a controlled manner by simply changing the synthesis temperature. These nanoparticles were used as a reusable adsorbent to remove Cr (VI) from aqueous solution. The recovery efficiency was found to be highly dependent on environmental parameters, such as temperature and pH. In addition, it was demonstrated that the initial concentrations of both Cr (VI) and magnetite nanoparticles strongly influence the removal capability of these nanomaterials. Remarkably, the nanoparticle size has a key role on the Cr (VI) adsorption efficiency, which gradually increases as the diameter decreases due to the augmentation of the surface area. The low aggregation in the case of small particles that results from the low magnetization saturation values also contributes to the enhancement of the surface area available for Cr (VI) adsorption. In contrast, nanoparticles with larger sizes are more easily manipulated by a magnet, and the efficiency is largely maintained after five cycles. The adsorption process fits the Langmuir isotherm model well, and the reaction was found to follow a pseudo-second-order rate.

Background: The impact of CHROMIUM exposure was studied on liver, kidney, testis, spleen, cerebrum and cerebellum of male Wistar rats (80-100 g body weight).Methods: It was observed that treatments of rats with CHROMIUM (i.p. at a dose of 0.8 mg / 100 g body weight per day) for a period of 28 days caused significant increase in CHROMIUM content while declining the body weight along with the organ weight, except liver.Results: Decreased acid phosphatase (ACP) and alkaline phosphatase (ALP) activities were observed in most of the organs. Significant increases in the cholesterol contents of all the organs were associated with the significant decreases in the level of phospholipids. Lipid peroxidation decreased in liver and kidney while it increased in testis, cerebrum and cerebellum. Reduced glutathione (GSH) level was found to be increased in liver, spleen and cerebrum, and decreased in kidney and testis. Catalase acti It is suggested that CHROMIUM treatment at the present dose and duration induces general tissue toxicity by causing membrane damage due to changes in the relative proportion of cholesterol and phospholipids in the membrane structure. In addition, tissue specific toxicity is affected by lipid peroxidation in testis, cerebrum and cerebellum, and in other tissues increased GSH level or enhanced catalase activity prevents lipid peroxidation to occur due to reactive oxygen species produced from CHROMIUM transformation.

Recently laboratory studies had recognized the capability of alge, fungi, and bacteria in the removal of heavy metals from industrial effluent. In this research, growth of Aspergillus oryzae in the tanning house effluent, and its capability in CHROMIUM bioremoval were assessed. Aspergillus oryzae can grow in different concentration of Cr+, 120-1080  mg/l. Maximum biomass growth and CHROMIUM removal rate at pH, 3.3, Cr+3   concentration equal to 240 mg/l and inoculum size  equal to  0.12% (dry weight) were 0.25% (dry weight ) and 94.2%, respectively. Effects of various factors such as pH, temperature, shaking velocity and nutrients were also investigated. At optimum conditions (ie: pH=5; temperature=30ºC, shaking velocity = 150 rpm, and nitrogen source of dihydrogen ammonium phosphate concentration=0.3%), biomass growth and CHROMIUM removal rate were found as 0.45% of dry weight and 99.8%, respectively. Effect of detention time showed that after 30h, biomass growth and CHROMIUM removal rate were 0.28% and 97.6%, respectively. Statistical studies on factors such as pH, temperature, shaking velocity, type and concentration of nutrients on the “biomass growth” and “residual CHROMIUM”, showed that all of the factors had significant effects ( α = 0.05, P < 0.001 ). Therefore A.niger capable grows in the tannery industries effluent with 240 mg/l CHROMIUM and 97.6% CHROMIUM removal rate.

The Cr (VI) adsorption characteristics of platanus orientalis leaves and their ash were examined as a function of contact time, initial pH and metal ion concentration. Batch adsorption experiments were performed. The effects of Ca2+, Mg2+, Na+ and K+ on adsorption were studied. The effect of this adsorbent on COD in wastewater showed that 2g/L of adsorbent caused increase of 110mg/L and 76mg/L COD in deionized water in 120 minutes for platanus orientalis leaves and their ash , respectively. The maximum removal took place in the pH range of 6-7, contact time of 60 minutes and initial concentration of 2mg/L. Studies showed that the Freundlich adsorption model better fitted with the results than Langmuir with R2 > 0.85. The study showed platanus orientalis leaves ash was more favorable than living ones as well as in removing CHROMIUM from the aqueous solution.