RESUMO
This study utilizes a novel method, namely the combination of advanced oxidation processes with synthesized highly porous α-Fe2O3 nanoparticles and coagulation-flocculation with polyacrylamide, to investigate the effects on COD removal in alcohol vinasse. Highly porous α-Fe2O3 nanoparticles were prepared via a chemical precipitation technique. The characteristic of the synthesized α-Fe2O3 nanoparticles were determined by FT-IR, Raman spectroscopy, XRD, SEM, and N2 adsorption-desorption isotherms. The effect of different α-Fe2O3 nanoparticles loading for chemical oxygen demand (COD) removal efficiency was investigated. The results revealed that at α-Fe2O3 nanoparticle dose of 3000 ppm had the highest COD removal for vinasse. Then, central composite design (CCD) was used to optimize the operating variables such as pH, time, oxidant dosage, and coagulant dosage, and their optimum values were determined to be pH:7.36, 90 min, 17.89 wt% oxidant dosage, and 1.6 wt% coagulant dosage, to achieve a high COD removal efficiency in 70 â for alcohol vinasse (98.64%). Based on optimal conditions, the porous α-Fe2O3 nanoparticles possess superior catalytic activity in the advanced oxidation process compared to other treating methods. Also, the mechanism of the catalytic oxidation reaction is evaluated.
RESUMO
The main challenge in utilizing permeable reactive barriers (PRB) for remediation of metals-contaminated groundwater is determination of a proper low-cost reactive medium that can remove the desired contaminants simultaneously. In this study, the performance of different zeolite materials and nZVI-based adsorbents for cadmium (Cd) removal was compared. Further, a composite of the best nZVI and zeolite samples was synthesized with the removal efficiency of 20.6 g/kg and selected as the proposed adsorbent. Moreover, the characteristics of the composite were analyzed through different techniques (BET, XRF, XRD, FT-IR, FE-SEM and EDX). In addition, through kinetic and thermodynamic studies, the effect of temperature, pH, ionic strength and presence of other metal ions on Cd removal efficiency was investigated. According to the results, since sodium zeolite (NaZ) provides a large number of specific ion-exchange sites for decoration with nZVI, stabilizes nZVI, and prevents its aggregation and further leaching in the harsh environment, the NaZ-nZVI composite is capable of removing Cd by adsorption and is applicable in PRBs, and thus it seems that the aforementioned composite is a proper candidate for groundwater remediation from a wide range of metal ions.
RESUMO
The increasing demand for energy all around the world has led to a rise in greenhouse gases (GHGs), of which carbon dioxide (CO2) is the most important. CO2 is largely responsible for global warming and climate change. Processes such as carbon dioxide capture and storage (CCS), which have an effective role in climate mitigation, seem to be promising. In recent years, porous carbons, particularly activated carbons (ACs), have rapidly emerged as one of the most effective adsorbents of CO2. However, the implementation of pristine ACs in the real world is still hindered due to their physical and weak adsorption, which makes these adsorbents sensitive to temperature and relatively poor in selectivity. Hence, the surface modification of ACs is essential in order to improve their surface area, pore structure and alkalinity. Numerous studies have reported lignocellulose-based ACs as very promising adsorbents of CO2. In this review, the sources, health and environmental effects of CO2, and the abatement methods of GHGs are described. In addition, the capture and separation of CO2 from gas stream using various types of lignocellulose-based ACs are summarized. Furthermore, the key factors controlling the adsorption of CO2 by ACs (characteristics of adsorbents, preparation conditions, as well as adsorption conditions) are comprehensively and critically discussed. Finally, future research needs and prospective research challenges are summarized.
