In this study, the modification of multi-walled carbon nanotube (MWCNT) with a cationic surfactant (cetyl trimethyl ammonium bromide, CTAB) and its application for removal of Direct Blue 86 (DB86) was investigated. The raw and functionalized samples were characterized by Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The influence of operational parameters such as adsorbent dosage, initial dye concentration and pH were studied at 25oC. Understanding the mechanism of the adsorption, Langmuir and Freundlich models were used. The results indicate that the data for adsorption of DB86 onto raw and modified carbon nanotubes fitted well to Langmuir isotherm. The Langmuir adsorption capacities of raw and modified carbon nanotube for DB86 were established as 69.93 and 149.25 mg/g, respectively. Pseudo first and second-order models were adopted to evaluate data and elucidate the kinetic adsorption process. The rates of sorption were found to conform to pseudo-second order kinetic with good correlation. The adsorption experiments indicated that the capacity of modified carbon nanotubes is more significant than raw carbon nanotubes, thus it could be used as an effective adsorbent for removing anionic dyes from textile waste waters.

Background and purpose: Textile dye effluents have some potential risks which require effective treatment before discharging into the environment. Advanced oxidation processes can remove pollutants faster than other processes due to active hydroxyl radical production; therefore, increase the efficiency of dye removal. This study was aimed at investigating dye removal process using UVA/ZnO and UVA/TiO2 nanocatalysts.Materials and methods: This study was done in a batch reactor on synthetic and real samples and the effects of initial dye concentrations, TiO2 and ZnO nanoparticles dosage, time, pH and interference compounds on efficiency of dye removal was investigated. The Daphnia Magna was used for bioassay test.Results: The removal rates of dye in optimum conditions were 69% and 95.5% by UVA/ZnO and UVA/TiO2 processes, respectively and the optimum pH in the process was 9 and 2, respectively. In this study, the initial concentration of dye and COD were found to have adverse relation with removal rate of dye in two processes (p<0.05, r2 ZnO=0.99, r2 TiO2=0.94). With increasing the catalyst and exposure time at both processes the dye removal rate increased. In this study, LC50 96 h decreased from 96.7 to 44.7 mg/l.Conclusion: The current study showed that TiO2/UVA process with effective optimization of operational factors, has high performance in R.B 86 dye decolorization and reducing toxicity.

Introduction: High volumes of wastewater along with contaminants, such as colloids and dyes are discharged from different industries into the environment. These wastewaters create major problems and serious threats for water resources. Therefore, it is essential to treat such wastewaters and reach the effluent discharge standards. In this regard, chitosan as a coagulant has a comparable performance with other coagulants. Moreover, the addition of chitosan and removal of turbidity probably lead to higher efficiency of nanoparticles in lower dosages which is investigated in the current study. Therefore, the purpose of this study was to investigate the efficiency of chitosan and magnesium oxide (MgO) nanoparticles for the removal of color and turbidity. Materials & Methods: Synthetic wastewater was prepared by mixing specific amounts of bentonite and direct blue 71 dye in distilled water. After the preparation of different concentrations of color and turbidity, the experiments were conducted with different dosages of chitosan and MgO separately and in combination. The influence of variables such as pH, initial concentration of dye and turbidity, MgO and chitosan dosages on removal efficiency was investigated in this study. Fidings: According to the results, the highest rate of color and turbidity removal was obtained at 1. 5 mg/L chitosan in combination with 1. 5 g/L MgO with the efficiency of 97. 5%. In addition, the highest removal efficiency was obtained at pH of 7. Discussion & Conclusions: Due to the need for high doses of MgO in high turbidities, the use of chitosan as a coagulant can be effective in reducing the use of MgO.

Direct Blue 86 (DB86), commonly used as a textile dye, can be degraded photocatalyticaly in aqueous solutions using TiO2 suspensions. A 400 W UV-A lamp was used in a batch circulating photo-reactor, without any dead zone. An initial concentration of 50 mg/L of dye, as a typical concentration in textile wastewaters, was used and the influence of catalyst concentration, pH and temperature were investigated. The experiments showed that degradation of dye can be effectively occurring in the both branches of photolysis (only UV) and photocatalysis (UV/TiO2). Accordingly, the optimum operating conditions of: catalyst concentration: 40 mg/L, pH of 4 and temperature of 40oC were obtained. Under these conditions, a degradation of about 96% and a mineralization of about 87% (based on COD measurements) of dye were achievable during about only 120 min.

In this study, chitosan (CS) stabilized bimetallic zero-valent iron (ZVI)-nickel (CS-nZVI-Ni) nanoparticles were synthesized for the removal of Direct Blue 86 (DB 86) from aqueous media. Analysis of the CS-nZVI-Ni characteristics was investigated by scanning electron microscope, energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and Brunauer-Emmett-Teller methods. The effective experimental parameters, including pH of the solution, contact time, adsorbent dosage, and initial dye concentration were evaluated to obtain optimum conditions. Results disclosed that the maximum removal values were related to the pH of 4, an adsorbent dosage of 0.2 g, contact time of 15 min, and a dye concentration of 20 mg/L. Experimental data were fitted to the Freundlich isotherm and Pseudo-second-order with the coefficient of determination (R2) equal to 0.9991 and 0.9994, respectively. The maximum adsorption capacity (qmax) was 61.72 mg/g from the Langmuir isotherm. All these results prove that prepared CS-nZVI-Ni could be considered as an adsorbent with high efficiency and cost-effectiveness for dye removal and as an alternative to other adsorbents.

This article describe the adsorption of acidic and direct dyes, namely Acid Red 14 (AR14) and Direct Yellow 86 (DY86), from aqueous solution onto activated carbon from walnut shell (ACW) as an eco-friendly and low cost adsorbent. Laboratory prepared ACW were characterized by Barrett-Joiner-Halenda (BJH) and Brunauer-Emmett-Teller (BET) pore structural parameters. The effect of various experimental parameters such as initial dye concentrations, pH and ACW doses were investigated in a batch adsorption technique. Optimum conditions for removal of dyes were found to be pH=1 and 1g of adsorbent dosage in equilibrium time of 48 h. It is shown that, lower equilibrium uptake further increase in temperature, because of the exothermic dyes biosorption process. The plot of the removal versus adsorbent dosage shows the effect of the different frequency of ACW dyes. Equilibrium adsorption isotherms were measured and the experimental data were analyzed using Langmuir, Freundlich and Temkin isotherm equations. It was found that data for DY86 Temkin isotherm is preferred (R2=0.93), while for AR14, the Freundlich isotherm is more applicable (R2=0.65). The ACW might be successfully used for the removal of dyes from liquid industrial wastewater.

This article presents the synthesis method of 5,11,17,23-para-tert-butyl calix[4]arene and 5,11,17,23- tetrasulfonic acid calix[4]arene (4-S-calix[4]) and the use of 4-S-calix[4], the sulfonated derivative of 5,11,17,23- para tert-butyl calix[4]arenea, as a very efficient molecular host for the adsorption of Direct Yellow 86, an azo dye, in an aqueous environment. Para-tert-butyl calix[4]arene and sulfonated derivative of para-tert-butyl calix[4]arene were identified using Fourier transform infrared spectroscopy (FTIR). Due to its stability and rigid conical form, this chemical displays potency potential in host-guest interactions. Hence, the compound 4-S-calix[4] was used as a guest molecule in order to examine the characteristics of the complex and the absorption intensity of Direct Yellow 86 dye. The estimation of the formation constant (Kf) for the complex between 4-S-calix[4] and DY86 was conducted by comparing the absorption intensity. The formation constant was predicted to be 4.6×104 M-1. The stoichiometric ratio of the compound was discovered to be 1:1 by the use of the Benesi-Hildebrand diagram.

BACKGROUND AND OBJECTIVES: The textile industry is known to produce large amounts of dyes and other harmful contaminants. This issue is of great importance as it adversely affects both water resources and the well-being of organisms. To address this issue, biochar is frequently used as a sustainable and environmentally friendly material for removing chemical contaminants during wastewater treatment. The aim of this study was to evaluate the viability of utilizing biochar obtained from banana peels as a promising bioadsorbent for reducing environmental pollution caused by direct navy blue dye. The research investigated various factors such as temperature, potential of hydrogen levels, particle size, and concentrations to determine the effectiveness of biochar in dye removal.METHODS: The biochar obtained was separated into powdered and granular forms based on particle sizes of 425 and 850 micrometer, respectively. The biochar's textural characteristics were assessed through nitrogen adsorption/desorption isotherms. Fourier transform infrared spectroscopy and the Boehm method were employed to analyze and measure organic functional groups, specifically acidic groups, for identification and quantification purposes. Batch experiments were performed to ascertain the effects of the initial concentration and potential of hydrogen on the adsorption capacity and removal percentage.FINDINGS: The results indicated that the powdered biochar obtained at 500 degrees Celsius had the higher surface area, with a value of 80.4 square meter per gram. The biochar demonstrated remarkable removal percentages, achieving 97 percent at the lowest concentration and 89 percent at the highest concentration, when the potential of hydrogen was adjusted to a value of 6. The Freundlich model gave the best fit to the experimental data for this biochar and obeyed pseudo second order kinetics, with correlation coefficients of 0.93 and 0.99, respectively.  CONCLUSION: This study provides evidence of the high removal efficiency achieved by biochar derived from banana peel waste in the removal of direct navy blue dye. Precise temperature control during the calcination process is essential to ensure its favorable chemical and textural properties. The unique attributes of banana peel biochar position it as an exceptionally promising adsorbent material. Not only is it cost-effective and environmentally friendly, but it also outperforms current wastewater treatment technologies in terms of competitiveness. Its remarkable ability to reduce contaminants, particularly the removal of dyes, further solidifies its potential as a highly effective solution.