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Go to Editorial ManagerDyes are important chemicals in industrial uses; however, they are considered hazardous materials because they accompany sewage and are one of the causes of serious diseases such as cancer if not treated properly. The aim of this study is to specify the effect of dyes on the environment and human health and to remove them from water using the photochemical agent (polyoxometalate). By studying two types of Phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) due to the good possibility of loading these acids on other materials using mixing and precipitation ways and without the need for high temperatures, as they are prepared at room temperature. They are also solid materials that are easy to separate, quickly dissolve in water, non-toxic, and do not release dangerous gases, which led to the need to use them in removing dyes, as they gave high efficiency. The research explains a comprehensive review of the use of PTA and PMA acid in Visible light-enhanced degradation of organic dye pollutants for three dyes: methylene blue, methyl orange and chromium B. Previous research is reviewed, with special emphasis on the performance of the photocatalyst, conditions that increase its efficiency, and the proposed mechanisms for the combined photocatalysts of PTA and PMA acids in developing the photocatalytic process. Finally, recent findings in this area are discussed, and possible future research continuations are suggested.
This study focuses on reuse of biowaste material locally available as spend coffee to synthesis high surface area biochar and evaluate its potential to remove dyes with acidic and basic in nature, as Acid Fuchsin and Methylene Blue dyes. The biochar was fabricated using chemical activation with various concentrating (20, 30, 50) vol. % of phosphoric acid (H3PO4). The pyrolysis process carried out in a tubular furnace under flow of nitrogen (N2) at 600°C for 3 hours. The final prepped biochar was analyzed using various techniques such as XRD, SEM, FTIR, TGA, EDX, N2-adsorption, BET, and pore volume (Vpore). Furthermore, batch adsorption experiments were conducted to remove Acid Fuchsin and Methylene Blue dyes from aqueous solutions under different variables of pH of solution (2-8), contact time (0-240) min, initial dye concentration (20-200) ppm, and weight of dosage (0.1-0.5) g/L. The results show that the best surface area and pore volume has been archived for the prepared biochar at 30% H3PO4 concentration were (1385.269 m2/g and 1.12 cm3/g) respectively. As well as, the maximum removal percentage was 92.5% for Fuchsin dye and 90% for Methylene Blue dye achieved at 180 minutes of adsorbing time, with maximum removal achieved with initial dye concentration of 20 ppm, 6.5 pH solution, and 0.3 g/L adsorbent. The study found that Freundlich isotherm and kinetic adsorption models fit well with the batch experimental data, which indicates homogenous distribution and limiting active sites with adsorption capacity (384.61) mg/g and (357.14) mg/g for Acid Fuchsin and Methylene Blue dyes, respectively. While, the pseudo-second-order kinetic model indicates a physic-sorption is the limiting step.
The usage of non-toxic, eco-friendly natural dyes on textiles has achieved notable attention due to increased environmental attention about avoiding hazardous synthetic dyes. This has prompted a return to natural dyes and the search for new sources, especially locally available ones like licorice. In this study, Glycyrrhiza glabra extract (70 g/l), prepared using ultrasound assistance, was used to dye cotton samples. The natural dyeing process employed a simultaneous mordanting method with zinc chloride and alum as mordants, in many concentrations (1, 3, 5, 7 and 10 g/l). The color fastness of the dyed samples was evaluated using a scanner and ImageJ. The fastness of the dyed fabrics was tested against washing and rubbing, and samples with licorice extract showed excellent stability. A tear strength test was also conducted to assess the impact of licorice extract dyeing on the mechanical properties of the samples. It was observed that dyeing with licorice reduced the tear strength, but increasing the concentration of mordants improved the resistance to tearing, making the mordanted samples stronger than the mordanted ones.
Industrial activities significantly affect the environment by releasing many organic pollutants, including industrial dyes, phenols and antibiotics, which produce wastewater. Effective removal of these substances from wastewater has appeared as a noticeable research field owing to its environmental significance. Exorbitant operational expenses and the potential generation of supplementary pollutants load conventional techniques like adsorption, membrane separation, and coagulation. Semiconductor-based photocatalysis has effectively degraded organic contaminants into less toxic or biodegradable compounds. The construction of robust visible-light-sensitive photocatalytic hybrids for environmental decontamination is an inspiring task for researchers. The exceptional photocatalytic performance of silver halides (AgX, where X is I, Cl, and Br) has recently attracted significant consideration as photocatalysts. Moreover, the combination of silver halides with other photo-active semiconductors to create efficient visible-light-driven photocatalyst heterojunctions has significantly promoted the broader application of the photocatalysis process with enhanced efficiency. Ag-silver halides/semiconductors heterojunctions have developed as crucial components in efficient composites for photocatalysis through surface plasmonic actions, helping with visible light absorption. The current study overviews the most recent Ag and silver halide-based composite photocatalysts. Additionally, it provides an essential understanding of their promoted photocatalytic performances and their main applications in organic pollutant degradation. Moreover, the photocatalytic mechanisms and environmental applications of AgI and composites were discussed.