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This research was conducted to study the adsorption of ammonium ions onto pumice as a natural and low-cost adsorbent. The physico-chemical properties of the pumice granular were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Modeling and optimization of a NH4+ sorption process was accomplished by varying four independent parameters (pumice dosage, initial ammonium ion concentration, mixing rate and contact time) using a central composite design (CCD) under response surface methodology (RSM). The optimum conditions for maximum removal of NH4+ (70.3%) were found to be 100 g, 20 mg/l, 300 rpm and 180 min, for pumice dosage, initial NH4+ ion concentration, mixing rate and contact time. It was found that the NH4+ adsorption on the pumice granular was dependent on adsorbent dosage and initial ammonium ion concentration. NH4+ was increased due to decrease the initial concentration of NH4 and increase the contact time, mixing rate and amount of adsorbent.

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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, andt = 12 h). Nickel oxide andn-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. [ABSTRACT FROM PUBLISHER]