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Effect of Magnetite Oxide Nanoparticles and Tungsten Oxide Nanoparticles on Phosphate Removal from Aqueous Solutions

EL-Baz Amro, Mokhtar Mona, Abdo Ahmed

Journal of Ecological Engineering

2023

Vol. 24, nr 3

287--303

Phosphate (P) removal from aqueous solutions were studied by a new mineral adsorbent, tungsten (VI) oxide (WO3) nanoparticles (NPs), which has not been the subject of much research in the field of removing P contaminants from agricultural wastewater. In this paper, P was removed from aqueous solutions by a new mineral adsorbent, WO3 NPs and it was compared with magnetite (iron IV) oxide (Fe3O4) nanoparticles (NPs) under the same ambient operating conditions i.e., The influence of the dosage of adsorbents, initial P concentration, contact time, pH and temperature. The values that achieved the best removal were recorded. It was concluded that the best limits for pH were at 2–3, contact time at 40 minutes, temperature at 45 °C and adsorbent dose at 1.0 g/L. Best results of the variables were applied on samples of real agricultural wastewater, which achieved removal ratio of 77.3% and 75.42% for Fe3O4 and WO3 NPs, respectively. SEM, EDX and FTIR images and analyses were conducted to describe the characteristics of nano-adsorbents used before and after P adsorption in aqueous solutions. The P adsorption kinetics for aqueous solutions were examined by fitting results of the experiment to both the first & second pseudo-kinetically models. The outcome indicated that kinematic data fit better with pseudo-second-order kinetic models. Moreover, the information captured from equilibrium adsorption was analyzed using isothermal methods (by Langmuir & Freundlich Forms). Their results showed that the Freundlich form is considered more suitable than Langmuir form in analyzing the biosorption of P ions. The thermodynamic demeanor of P adsorption by Fe3O4 and WO3 NPs was analyzed and evaluated, and the thermodynamic data analyses confirmed the process of P adsorption was spontaneous. The ΔG° value was negative, while ΔH° and ΔS° values found to be positive, which means that the adsorption of P was a spontaneous, random and endothermic operation. In general, Fe3O4 and WO3 nanoparticles had a high efficiency in removing phosphate from water. In addition, WO3 NPs has been identified as one of the most promising adsorbents due to its rapid and effective adsorption of pollutants.

Impact of Nanoparticles on Biogas Production from Anaerobic Digestion of Sewage Sludge

Heikal Ghada, Shakroum Mohamed, Vranayova Zuzana, Abdo Ahmed

Journal of Ecological Engineering

2022

Vol. 23, nr 8

222--240

Since anaerobic digestion (AD) is the preferred procedure for sludge treatment and disposal, it is constrained by the hydrolysis and acidogenesis stages. Nanomaterials have an impact on the AD process due to their unique properties (large specific surface areas, solubility, adsorption reduction of heavy metals, degradation of organic matter, reduction of hydrogen supplied and catalytic nature) which make them advantageous in many applications due to their effectiveness in improving the AD efficiency. Magnetic Nanoparticles (MNPs) were used in the present study to improve the biogas production. The experiments were divided into two stages to evaluate the effect of adding MNPs to two types of sewage sludge (SS): attached growth process (AG) and activated sludge (AS). The first stage consists of 15 tests divided into three experiments (A, B, and C). Doses of MNPs (20, 50, 100, 200) mg/l were added to all digesters in the same experiment except for one digester (the control). Experiments A, B and C achieved the highest biogas production when 100 mg/l of MNPs was added. They were 1.9, 1.93 and 2.07 times higher than the control for A, B and C respectively. The second stage consists of 12 tests with a pretreatment for some of SS. It was divided into two experiments (D, E), where the chemical pretreatment was applied to experiment D and the thermal pretreatment was applied to experiment E except for the control. For digester D4, which had 100 mg/l of MNPs after a chemical pretreatment at pH = 12, the biogas production increased by 2.2 times higher than the control (D0) and 1.5 times higher than the untreated sludge with the addition of 100 mg/l MNPs (DN). Thermal pretreatment at 100 °C with addition of 100 mg/l MNPs (E4) achieved a biogas yield 2 times higher than the control (E0), and 1.39 times higher than untreated sludge with 100 mg/l MNPs (EN). The previous results indicate that the integration of magnetite can serve as the conductive materials, promoting inherent indirect electron transfer (IET) and direct interspecies electron transfer (DIET) between methanogens and fermentative bacteria which lead to a more energy-efficient route for interspecies electron transfer and methane productivity. This study demonstrated the positive effect of magnetite on organic biodegradation, process stability and methane productivity.