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The present study aimed at investigating phosphoric acid (1, 6 and 12 N)–modified pumice efficiency in removal of malachite green (MG) dye from aqueous solutions. The effects of different parameters such as pH (3–11), adsorbent dosage (0.2–1.4 g/L), contact time (15–75 min) and the dye initial concentration of 85 mg/L were analyzed. The obtained modified pumice was characterized using the Fourier transform infrared spectroscopy and scanning electron microscopy. Adsorption equilibrium data were analyzed using Langmuir, Freundlich, Temkin and Redlich–Peterson. The results illustrated that the data were following both Langmuir and Freundlich isotherms. Also, the phenol absorption was modeled using pseudo-first order, pseudo-second order, intraparticle diffusion and Elovich models. The best fit being observed with the pseudo-second-order kinetic model. Finally, the process modeling was carried out using response surface method and artificial neural networks.

Malachite green (MG) is a synthetic dye which is widely used as biocide in aquaculture and dyeing agent in textile industries. This dye could be difficult to remove from aquatic environments due to its features and low degradability. According to the effect of ferrous on the physical and chemical characteristics of scoria, this study was to evaluate iron-coated scoria performance in removing MG from aqueous solutions. Adsorption process is carried out in vitro at different pH, adsorbent dosage, contact time, and constant concentration of the dye. Results indicated that all parameters of the model were inaccurate ranges, which confirm the validity of the obtained model to predict the amount of MG removal. Moreover, MG removal rate increased with increasing the pH, the adsorbent dosage, and the contact time. The highest efficiency was 94.2% obtained at pH = 11, adsorbent dose = 1.4 g/L, and contact time = 75 min. Adsorption of MG on iron-coated scoria was found to follow both the Langmuir and Freundlich isotherms and pseudo-second-order kinetic model. The separation factor and adsorption intensity in the iron-modified scoria were obtained lower than the bare scoria. According to the results, it can be concluded that iron via chemical changes of adsorbent structure causes increase in the efficiency of scoria for removal of MG.

It is hard to remove malachite green from aquatic environments due to its low degradability and other features. Based on the effect of manganese on physical and chemical characteristics of scoria, the aim of this study is to evaluate the manganese–coated pumice performance in removing malachite green (MG) from aquatic environments. Response surface methodology (RSM) based on the central composite designs (CCD) was used to assess the effects of independent variables including pH (3, 5, 7, 9, and 11), adsorbent dosage (0.2, 0.5, 0.8, 1.1, and 1.4 g/L), contact time (15, 30, 45, 60, and 75 min), and constant concentration of the dye (85 mg/L) on the response function and the best response values were predicted. The results indicated that the dye removal increases with increasing the pH value, absorbent dosage and contact time, whereas MG concentration has an antagonistic effect on sorption system. Moreover, the optimum dye removal efficiency (99.9%) was achieved in pH = 11, adsorbent dose = 1.4 g/L, and contact time = 75 min. The adsorption process fitted well with the Langmuir model which, indicated the presence of heterogeneous sites for to adsorption MG dye and also this process followed the pseudo-second-order model. According to the results, the modified pumice with manganese could be successfully used for MG adsorption in the aqueous solution rather than natural scoria due to wide chemical changes of adsorbent structure.

The aim of this study was to compare the performance of down- and up-flow non-selective strong anion exchange resin (A400E) in the removal of nitrate from drinking water due to loading rate, height and volume of resin, as well as passing water volume. In this study, totally, 270 samples were taken and analyzed for evaluating the amount of outcome nitrate. The results showed that the trend of removing nitrate decreased in terms of increasing the passing water volume and loading rate in both systems. While the altitude of ion-exchange column increased due to the up-flow, the removal efficiency of nitrate increased continuously. In the down-flow resin, the efficiency of the system was gradually reduced while increasing the height of resin up to 60 cm; whereas the system efficiency increased at the resin height of 60–90 cm. The efficiency of both ion-exchange systems were affected as a result of the some factors including volume of passing water, resin height, and loading rate at high, medium, and low levels, respectively. Overall, to achieve the sufficient water quality, it is required to consider the height of resin and amount of passing water volume to reach the cost and effectiveness of the system.

AbstractMalachite green (MG) is one of the most used dyes in textile industries. The aim of this research work was to degrade MG, a model dye, using nickel-doped TiO2nanocatalysts. Nickel-doped TiO2nanocatalysts were fabricated under mild hydrothermal conditions (p = autogenous, T = 100°C, and t = 12 h). Nickel oxide and n-butylamine were used as dopant and surface modifier, respectively. The samples dried were characterized using powder X-ray diffraction, zeta potential, SEM, and electron diffraction X-ray analysis. The batch experiments of MG degradation were performed under UV light and sunlight irradiation. The effect of operational parameters including nanocatalyst dosage, pH, contact time, initial concentration of dye solution, and light source were investigated systematically. It was found that nickel-doped TiO2nanocatalysts had better solar degradation efficiency compared with bare TiO2under both UV light and sunlight irradiation. The optimum solar degradation efficiency for MG dye solution was achieved at pH 8, nanocatalyst dosage = 1.2 g/l, contact time = 120 min, and initial dye concentration = 250 mg/l.

Malachite green (MG) is one of the most used dyes in textile industries. The aim of this research work was to degrade MG, a model dye, using nickel-doped TiO2nanocatalysts. Nickel-doped TiO2nanocatalysts were fabricated under mild hydrothermal conditions (p = autogenous, T = 100°C, and t = 12 h). Nickel oxide and n-butylamine were used as dopant and surface modifier, respectively. The samples dried were characterized using powder X-ray diffraction, zeta potential, SEM, and electron diffraction X-ray analysis. The batch experiments of MG degradation were performed under UV light and sunlight irradiation. The effect of operational parameters including nanocatalyst dosage, pH, contact time, initial concentration of dye solution, and light source were investigated systematically. It was found that nickel-doped TiO2nanocatalysts had better solar degradation efficiency compared with bare TiO2under both UV light and sunlight irradiation. The optimum solar degradation efficiency for MG dye solution was achieved at pH 8, nanocatalyst dosage = 1.2 g/l, contact time = 120 min, and initial dye concentration = 250 mg/l.

Vermicomposting has recently been recognized as one of the most appropriate methods to stabilize organic waste. In terms of a system for waste management, vermicomposting is sustainable, economically viable, and without detrimental effects to human health or to the environment. The aim of this study was to evaluate the process of vermicomposting using an indigenous species of earthworms (Eisenia fetida) on a small domestic scale as a system for waste management.This study was carried out as an experiment using the following procedure: a plastic container was prepared for vermicomposting; then, a bed was prepared in a ready container with a layer of initial bedding, sieved garden soil, and compostable waste. It was inoculated with Eisenia fetidaearthworms. Samples were taken after 30 and 90 days of vermicomposting, and measurements were taken for the following parameters: percentage of organic matter, phosphorus, total carbon, total nitrogen, moisture content, ash, electrical conductivity, and pH. Results for percentage of organic matter, phosphorous, ash, total carbon, total nitrogen, carbon/nitrogen ratio, electrical conductivity, moisture content, and pH of mature compost after 90 days were 42 ± 2.8, 53 ± 0.17, 22 ± 0.170, 1.12 ± 0.003, 20 ± 0.25, 2.8 ± 0.6, 1, 200 ± 200 cSu, 56 ± 5.5%, 8.3 ± 0.2, respectively, and all these parameters except moisture content were compared with the standards.According to these results, vermicomposting of municipal biodegradable waste by homeowners can be recommended as the best and most suitable method for solid waste disposal. This determines small-scale domestic vermicomposting as a suitable method for solid waste management. Reducing domestic waste at the source is an effective way to implement the main priorities of a waste management system in terms of its economy and its impact on the environment.