Current Environmental Engineering - Volume 5, Issue 2, 2018

Zero valent iron nanoparticles (nZVI or Fe0 nanoparticles) have received enormous attention in recent years due to their promising results against a vast variety of water contaminants. They have proven to be much more effective and fast, in comparison to granular ZVI against these contaminants, due to their small size and large specific surface area. But at the same time, the use of nZVI in water remediation has been limited due to its lower stability under ambient conditions. In order to increase its stability in water and enhance its water decontamination efficiency; the composites of nZVI with clays, polymers, carbon derivatives, metal oxides, biomaterials and polymeric resins are being prepared and studied enormously. This review focuses on the application of nZVI composites for the removal of numerous organic and inorganic toxicants from contaminated water. The plausible mechanism involved in the removal of different types of contaminants has also been discussed.

Background: The healthy agricultural soil is essential for the safeguard of the environment. According to the UAE Ministry of Environment and Water (MOEW) and Environmental Agency - Abu Dhabi (EAD), the soil of the UAE is considered as one of the most challenging soils around the world. It is very fragile, sensitive and very slowly renewable. A healthy soil includes certain amounts of elements, which can guarantee growing healthy crops and best yields. Aim: To ensure the former, a comprehensive soil survey of 100 agricultural farms in the United Arab Emirates (UAE) was performed. Method: The objective of this soil survey was to establish the first documented baseline concentration of UAE soil minerals, trace, and heavy metals contents. Result: The mean values (mg Kg-1) were: Al - 8,539.7, As - 2.17, B - 47.68, Ca - 86,264.5, Cd - 0.35, Co - 10.30, Cr - 111.20, Cu - 14.32, Fe - 9,839.80, K - 2,026.80, Mg - 26,688.30, Mn - 237.40, Mo - 0.02, Na - 470.40, Ni - 60.90, P - 450.60, Pb - 4.25, S - 2,393.50, Si - 795.68, Sr - 593.70, V - 20.90 and Zn - 24.90. Conclusion: Further, study results were compared against international recommended levels. In addition, we provided recommendations to UAE concerned entities regarding regulating the concentrations of these elements found in the agricultural soil. Future research recommendations include extending the study scope to cover all the agricultural farms in UAE including organic farms. Study results supported mineral mapping of UAE soils using the Geographic Information System (GIS).

Background: The change in land use has increased flood risk in Tunisia. Objective: This paper evaluates the impact of such changes on the Mellegue River basin in Tunisia. Method: The semi-distributed (Hydrologiska Byråns Vattenbalansavdelning) HBV-Light hydrological model and remote sensing for two different periods were used in the evaluation. ArcGIS software was used to generate land use/cover maps. The accuracy of the classified maps was assessed using contingency matrix. Result: The results show that the forest area decreased by 5% from 1988 to 2003 due to anthropogenic activities. As well, the irrigated land increased by 4% due to development of advanced agricultural techniques and governmental support to increase agricultural yield. Model calibration and validation using GAP optimization for land use in 1988 and 2003 gave an efficiency of 0.38 and 0.33, respectively. The validation results slightly decreased compared to the calibration step. Conclusion: The paper showed that deforestation was the main factor of increasing the runoff from 1988 to 2003.

Background: Membrane technology using Spiral Wound Reverse Osmosis (SWRO) is long established as a large scale industrial membrane process for desalination. Membranes need to be managed after their life cycle. Aim: The present study involves the AOP studies for liquefaction and depolymerization of desalination membranes under batch reactor mode. Method: Advanced Oxidation Process (AOP) based hydrothermal liquefaction process techniques have been carried out for Ultra Filtration (UF) membranes; permeate spacer and RO membranes at different stirring rates, temperatures, concentrations and reaction durations. Result: The comparison of process techniques under dynamic conditions for liquefaction and depolymerization of permeate spacer/UF & RO membranes are presented with an objective for facilitating chemical recycling or disposal of the same. Conclusion: The synergistic effect of radiation with concentration of reaction media is established.

Objective: A supermagnetic halloysite/Fe3O4/Au nanoparticles (HNT/Fe3O4/AuNPs) nanocomposite was fabricated by a facile non-covalent self-assembly approach and used as a recyclable catalyst for the hydrogenation of Congo Red (CR) and 4-nitrophenol (4-NP). Method: The AuNPs were successfully decorated onto the HNT/Fe3O4 carrier using natural polymer chitosan (CTS) as a “bridge”. The formation of the nanocomposite and the uniform distribution of AuNPs on the HNT/Fe3O4 carrier were confirmed by UV-vis, FTIR, XRD, TGA and TEM analyses. Due to the successful loading of small-size AuNPs, the resulting HNT/Fe3O4/AuNPs nanocomposite showed very good catalytic activity. At a low catalyst concentration (0.25-0.5 g/L), the nanocomposite can catalyze the rapid decoloration of the 25 mg/L CR solution within 4 min and rapid reduction of 4- nitrophenol (4-NP) into 4-aminophenol (4-AP) within 5 min through a catalytic hydrogenation reaction in the presence of sodium borohydride. Result: In the catalysis reaction process, the AuNPs acted as the “courier station” to promote the electron transfer and thus accelerated the reaction process. After reusing for 8 catalysis cycles, the catalytic activity of the nanocomposite still remained good. In addition, the nanocomposite showed the maximum magnetization rate of 33.6 emu/g, which made it easy to separate it from the solution by a magnet for recycling and reusing. Conclusion: In a word, the nanocomposite has potential to be used as a high-efficient catalyst for the decoloration of dye and conversion of 4-NP by a hydrogenation reaction.

Objective: Adsorption studies were performed in equilibrium and kinetic modes using the solution containing Reactive blue 19 dye as adsorbate and sugarcane bagasse as an adsorbent. Observation: The dye removal efficiency was found to increase from 12.88 to 57.81% with an increase in the adsorbent dose from 1.5 to 15 g/L for a solution with an initial dye concentration of 80 mg/L. The dye removal efficiency was also found to increase from 60.82 to 73.59% with an increase in the salinity of the dye solution from 2 to 10 g/L. A significant increase in the dye removal efficiency (from 8.33 to 74.22%) was observed with change in the solution pH from 9.5 to 11.5. The equilibrium study results were found to be in agreement with the linear isotherm. Adsorption kinetic studies were carried out and it was observed that most of the dye adsorption is accomplished in a contact time of 120 min. A new kinetic model has been proposed to analyze data. Result: The kinetic experimental data was found to be in good agreement with the proposed model.