The primary, most obvious parameter indicating water quality is the color of the water. Not only can it be aesthetically disturbing, but it can also be an indicator of contamination. Clean, high-quality water is a valuable, essential asset. Of the available technologies for removing dyes, adsorption is the most used method due to its ease of use, cost-effectiveness, and high efficiency. The adsorption process is influenced by several parameters, which are the basis of all laboratories researching the optimum conditions. The main objective of this review is to provide up-to-date information on the most studied influencing factors. The effects of initial dye concentration, pH, adsorbent dosage, particle size and temperature are illustrated through examples from the last five years (2017–2021) of research. Moreover, general trends are drawn based on these findings. The removal time ranged from 5 min to 36 h (E = 100% was achieved within 5–60 min). In addition, nearly 80% efficiency can be achieved with just 0.05 g of adsorbent. It is important to reduce adsorbent particle size (with Φ decrease E = 8–99%). Among the dyes analyzed in this paper, Methylene Blue, Congo Red, Malachite Green, Crystal Violet were the most frequently studied. Our conclusions are based on previously published literature.

Based on the well-known excellent adsorbent ability of chicken eggshells, the adsorptive capacity and mechanism of Remazol Brilliant Violet-5R (RBV-5R) dye by eggshell was investigated. Exploiting the high surface-area-to-volume ratio and porous structure of this natural adsorbent, the developed procedure showed to be useful for the efficient adsorption of RBV-5R dye from contaminated water. The protocol was thoroughly optimized by investigating the effect of the dye concentration, biomasscontaminated water ratio, particle size of the adsorbent, pH and temperature, as they are key factors in the efficiency of the dye removal process. The eggshell material was characterized by different types of microscopy techniques (stereo, polarization, SEM) as well as elemental analysis (element distribution mapping, EDX), Raman spectroscopy and BET-surface density measurements. EDX, FTIR and Raman spectroscopy proved the presence of the adsorbed dye on the surface of the biomaterial. It was shown that under optimal conditions, the environmentally friendly and inexpensive eggshell could be a reliable adsorbent for Remazol dye removal from wastewater. One of today's global challenges is to supply healthy, pure and consumable water to safeguard public health since a growing variety of toxic organic and inorganic pollutants are occurring in water bodies 1. According to the 2015 World Water Development Report, the demand for water around the world will increase by 55% over the next 15 years, indicating that the Earth's current water supplies can cover only 60% of our future needs by 2030 2. With rapid industrial development, the overexploitation of natural resources, industrial and natural disasters, the number of polluted water sites contaminated with heavy metals 3-6 , radioactive elements 7,8 , nitrite 9,10 , phosphate 11,12 , pesticides 13 , dyes 14-16 , etc., are continuously increasing. Dyes are widely utilized in the paper, pulp, paint and textile industries, with a large amount of water demand for washing and cleaning purposes. Based on the Colour Index, currently, more than 10 000 various types of synthetic dyes are available worldwide. In 2014, more than 1.5 million tons of dyes were produced annually. Fifty percent of these dyes are used by the textile industry, where during the colouring process, 1-10% of these dyes are discharged 17,18. Due to the high solubility and low biodegradability of these compounds, dye-polluted industrial wastewater is one of the most difficult types of wastewater to clean. Remazol Brilliant Violet-5R (RBV-5R), a reactive dye, is used to colour cellulosic fibres. After the colorization process, approximately 10-50% of the initial dye load remains unused 19. Biosorption is a promising method for removing persistent compounds, i.e., non-biodegradable compounds. Recently, various materials such as nanocomposites, households and industrial wastes have been used as biosorbents for inorganic and organic contaminant removal 5,11,20,21. Coconut residual fibres 22 , low-cost activated charcoal from to...

The atmospheric stability plays an important role in the accumulation of air pollutants and greatly influences their degradation, dispersion and deposition. These atmospheric qualities can be determined with various methods (Richardson number, Monin -Obukhov length, SRDT method) and the pollutant concentration increase demonstrates the atmospheric stability. In this study the cold periods were the most stable as well the PM 10 and CO pollutants had high concentrations. Between these two pollutants the correlation is high because their sources are the same: transport and biomass burning. The study of hourly averages highlighted the importance of traffic intensity since the concentration variation follows the traffic intensity. An increase in the wind speed in the basin results in the pollutants concentrations decrease, the negative correlation with the temperature indicating the importance of the photochemical processes.

Eggshell waste as adsorbent was successfully used for the removal of Cd(II) ions from model synthetic aqueous solutions. Batch biosorption studies were conducted in order to evaluate the effect of various parameters, such as: contact time and initial metal ion concentration. The changes in the morphological structure were evaluated by TEM and SEM analysis. The experimental isotherm data were analysed using Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm equations, using regression analysis linear and non-linear form. Langmuir model was found to be in better correlation with experimental data (R 2 =0.99). Biosorption kinetics data were tested using pseudo-first-order, pseudo-second-order, intra-particle and liquid film diffusion models. Kinetics studies showed that the biosorption followed a pseudo-secondorder reaction. Removal efficiencies up to 92 % and a maximum adsorption capacity of 8.2 mg/g Cd(II) were obtained experimentally and 7.14 mg/g Cd(II) were obtained from Langmuir isotherm model. The percentage of metal sorption (C i =11 mg/L, E,(%)=92.42), EDS analyses, and bioconcentration factor were also calculated. The investigation findings suggested that the physical adsorption is controlling the adsorption rate. Results of this study indicate that eggshell waste can be effectively used for the removal of Cd(II) ions from aquatic environments. The process is feasible, reliable and eco-friendly.

In the last years, the adsorption processes were proven effective and easy to use techniques to clean polluted wastewater. The purpose of this research is to examine the biosorption method on organic indicators (Methylene Blue, Malachite Green, Congo Red and Bromphenol Blue) in aqueous medium by using chicken eggshell. The adsorption process was investigated in static circumstance. We examined the initial change of concentration (10-50 mg/l), the pH effect on the adsorption process, the equilibrium process, and the sorption kinetics. With scanning electron microscope, we examined the morphology and texture of the eggshell; furthermore, we conducted EDX microanalysis and ecotoxicological tests. Our results support the influence of the parameters on the sorption process.