نشریه مطالعات در دنیای رنگ
سال دوازدهم شماره 4 (پیاپی 47، زمستان 1401)

Organic dyes have attracted a lot of attention due to their long-term environmental toxicity and short-term damage to health. The process of photocatalysts with the use of semiconductors for efficient use of solar energy in the degradation of dye pollutants has received much attention for environmental improvement. Electron transfer is the most important and fundamental step in photocatalysts processes. The efficiency of electron transport is the function of the location energy level of valence layer and the conduction layer relative to the reduction potential of the adsorbed particles on the catalyst. One of the methods of preventing recombination of electrons/holes is direct conductivity of electron and holes to the other catalyst. This is possible using heterojunction photocatalysts with different valence and conduction band potentials. In other words, the coupling of two semiconductors, the valence and conduction bands, have different energy levels, causing more effective separation. The purpose of this study is to investigate different Load transmission mechanisms in pair and p-n junction photocatalysts.

The increasing use of synthetic hair dyes in Iran, the heavy metals present, side effects (skin sensitivities), and the risk of carcinogenicity have made researchers investigate these dyes. This study was carried out by randomly selecting five Iranian brands in the city of Tehran and comparing them with two foreign brands. It was determined the concentration of heavy metals (Lead, Arsenic, Nickel, Cadmium, and Chromium) in domestically produced hair dyes had been investigated. Heavy metal concentrations were measured by inductively coupled plasma spectrometry (ICP MASS) following acid digestion. The results showed that the concentration of heavy metals in 35 samples measured with three repetitions was less than 10 ppm and within the permissible limit.

Today, nanostructured coatings are highly regarded as one of the most widely used areas of nanotechnology.</em> Destructive factors like friction, wear, and environmental conditions in instruments and parts of the medical industry cause surface destruction. Therefore, to solve this challenge, researchers have reduced the percentage of component destruction by using surface engineering and applying nanocoatings. Orthopedic and dental implants are increasingly used in the medical field because of their high success rates. Implant-associated infections, however, still occur and are difficult to treat. Using an active coating on the implant surface is recommended to prohibit infection in medical parts. This review article mentions the types of medical materials used, especially the properties of 316L stainless steel alloy and the improvement of its corrosion resistance properties by coating with chitosan and gelatin nanoparticles by the electrophoretic method. Also, the effect of nanoparticles has been investigated. It was observed that the addition of nanomaterials reduces the amount of deposition, but due to the increase in surface quality and the reduction of porosity in the coating, it increases the corrosion resistance</em>.</em>

In recent years, the textile industry has produced more than 50 % of the colored wastewater in the world. Clean water is essential in the lives of humans, aquatic organisms, and agricultural products. Due to their toxicity, dyestuff in water causes adverse quality, endangers their health, and causes environmental changes. There are different methods for wastewater treatment, which, based on the research, shows that today's surface absorption method is mainly used for wastewater treatment due to its cheapness, simplicity, and cost-effectiveness. In this article, the removal of dyestuff from wastewater was investigated using different nanocomposites, and the effect of adsorption with nanocomposites was investigated based on factors affecting adsorption, including contact time, initial concentration, the effect of temperature, and pH of the solution. Adsorbents significantly impact removing dyestuff and can perform wastewater treatment with good quality. This research used activated carbon nanocomposites, carbon nanotubes, silver nanoparticles, zinc ferrite, ZnO, TiO2</sub>, Fe3</sub>O4</sub> and zero-valent iron nanoparticles for wastewater decolorization. In this article, the results show that different nanocomposite adsorbents are promising. They are a promising future for the treatment of colored wastewater.  

The passage of time and the progress of humanity is always directly related to the increase of human desire for creative creation artworks. The presence of pigments in cultural heritage is one of the things that has a creative expression in the artworks. Moreover, it contains valuable information about the evolution process of history and humanity. In the previous part of the review, studies of pigments, white lead, and red lead were investigated. In continuation of scientific studies, the present review provides a comprehensive point of view on traditional pigments, emerald green and ultramarine blue. For this purpose, by collecting and reviewing the current knowledge of this field, researchers have evaluated pigments from some points of view, including their structure, application, evolution throughout history, general pigment properties, preparation, and synthesis methods. Furthermore, optical properties, particle characteristics and some chemical properties, identification methods, and types of degradation in these pigments were examined. This research tries to strengthen the scientific and technical investigation of historical pigments based on valid scientific data.

Lately, there has been an increase in dye manufacturing, resulting in increased environmental pollution. Recent studies show a wide availability of usage adsorbents, including banana peels, potatoes, algae, etc. Food and Drug Administration prohibited the use of Rhodamine B (RhB) for its toxicity and harmful effects. Therefore, this study presents a wide range of non-conventional low-cost alternative adsorbents to remove RhB dye from wastewater. It has been observed that the mechanism of the dye adsorption is focused on kinetics, isotherm, and thermodynamic models, which depend on the chemical nature of the materials and various physicochemical experimental conditions such as solution pH, initial dye concentration, adsorbent dosage, and temperature of the system. The kinetic data of adsorption of RhB dye usually follow the pseudo-first-order and pseudo-second-order kinetic models. Several studies revealed that Langmuir and Freundlich adsorption isotherm models are frequently used to evaluate the adsorption capacity of the adsorbents. Furthermore, thermodynamic examination showed that RhB adsorption was endothermic and unconstrained in nature. Thus, both photocatalytic degradation and adsorption methods offer good potential to remove RhB dye from industrial effluents. The work is in progress to evaluate the possibility of using other modified waste biomass for industrial pollution control.