Synthesis and Surface Modification of Hexagonal Mesoporous Silicate–HMS using Chitosan for the Adsorption of DY86 from Aqueous Solution

Many types of dyes are toxic, carcinogenic, non-biodegradable due to their complex aromatic structures and their water solubility and accordingly, they should be removed from wastewaters. In the present research, hexagonal mesoporous silicate HMS was synthesized by sol-gel method and after modification by natural polymer chitosan (Ch-HMS), it was applied for the removal of direct yellow 86 from aqueous media. The characterization of synthesized HMS and chitosan modified HMS were analyzed by some basic analyses such as SEM, FTIR, XRD and BET. The effects of pH, adsorbent dosage and contact time on the removal of direct yellow 86 were investigated. The results revealed that the maximum adsorption of dye was about 92% which was obtained by 0.075 g of Ch-HMS composite at the pH of 2 and for 60 min contact time. The equilibrium data of experiments were studied by Langmuir, Freundlich, Elovich and Temkin isotherm models using linear regression. The Langmuir model with the maximum adsorption capacity of 71.43 mg/g was the predominant model. Kinetic study was also performed using pseudo first and pseudo second order kinetic models where the second order model had the best agreement with the experimental data. The experimental data showed that surface modification of HMS by chitosan and formation of Ch-HMS nanocomposite enhanced the adsorption capacity of HMS and changed it into a useful and powerful adsorbent for the removal of pollutants from aqueous solutions

Investigation of the Performance of Zeolitic Adsorbent Modified with Cu Nanoparticles for Desulfurization of Hydrocarbon Fuel

Sulfur is one of the elements in fossil fuels that is converted to sulfur dioxide, which is one of the most important air pollutants, when burned in a car engine. In the present study, the adsorption capacity of an organic sulfurized compound from a diesel fuel model containing 300 ppm thiophene was evaluated using x13 zeolite modified with 3% by weight of copper metal. Moreover, the effect of three parameters of contact time (15, 30, 60, and 120 min), adsorbent value (0.5, 1, 2.5 and 3.5 g) and temperature (25, 40, 50 and 60 °C) was assessed in a discontinuous system. In order to activate the adsorbent surface cations, x13 zeolite was washed with deionized water and 0.1 M copper nitrate salt and then copper nanoparticles were loaded on it. The maximum adsorption capacity was 2.5 g of adsorbent at 60 min at room temperature, and the amount of thiophene for adsorption modified with copper nanoparticles increased from 300 to 138 ppm. The adsorption results showed that an increase of more than 2.5 g of adsorbent would not cause a significant change in the adsorption efficiency. In addition, FT-IR, SEM and N2 physisorption studies showed that the adsorbent would maintain its regular structure after nanoparticle loading. Finally, the modified zeolite showed better performance for desulfurization of the diesel fuel model

A state-of-the-art protocol to minimize the internal concentration polarization in forward osmosis membranes

© 2020 Elsevier B.V. The main reason for the lower water flux, than expected, in the forward osmosis (FO) process, is the internal concentration polarization (DICP). Usually, the structural parameter (S) is used as an indicator of the intensity of DICP. Small S value is desirable for the FO membrane due to the low DICP. However, due to design and construction problems, structural parameter reduction has some drawbacks. In this work, DICP reduction in FO membranes will be investigated using an approach other than structural parameter reduction. Accordingly, during the FO process, the feed solution (FS) valve is opened and closed at a constant period of time (feed valve timing (FVT)). Four types of FO membranes with different S parameters were used. The effects of the implementation of the proposed protocol on the water flux (Jw), reverse salt flux (Js), specific reverse solute flux (Js/Jw) and effective driving force were investigated. The effects of the S parameter and draw solution (DS) concentration also investigated separately. The results showed that the proposed protocol significantly increased Jw. Also, the values of Js/Jw decreased with increasing the FVT values and reached the lowest level in the practical recovery time (PRT)