Removal of Total Petroleum Hydrocarbons from Contaminated Soil through Microwave Irradiation.

In this study, we investigated the removal mechanism of total petroleum hydrocarbons (TPH) from soil by microwave heating. TPH contaminated soil was investigated to determine the desorption behavior of five carbon number-based fractions of TPH. The applied operating microwave power density influenced the final temperature that was reached during heating. For low operating power density applications, microwave effectiveness was limited due to the soil's dielectric properties, which exhibited a direct relationship with temperature variation. Soil particle distribution could be attributed to permeability, which significantly influenced the evaporation of contaminated soil during the microwave treatment. The results indicate that the activation energy was correlated with the influence of particle size. The removal efficiency of the coarse soil reached 91.1% at 15 min, whereas that of fine soil was low. A total of 30 min had passed, and a removal efficiency of 71.2% was found for the fine soil. Residual TPH concentration was decreased when irradiation time was increased with a removal rate dependent on soil temperature variation. The surface functional groups of the contaminated soil were influenced by microwave irradiation, and changes in the hydrocarbon fraction affected contaminant removal.

Effect of Soil Washing Solutions on Simultaneous Removal of Heavy Metals and Arsenic from Contaminated Soil.

In this study, we investigated the feasibility of using a solution of sulfuric acid and phosphoric acid as an extraction method for soil-washing to remove Cu, Pb, Zn, and As from contaminated soil. We treated various soil particles, including seven fraction sizes, using sulfuric acid. In addition, to improve Cu, Pb, Zn, and As removal efficiencies, washing agents were compared through batch experiments. The results showed that each agent behaved differently when reacting with heavy metals (Cu, Pb, and Zn) and As. Sulfuric acid was more effective in extracting heavy metals than in extracting As. However, phosphoric acid was not effective in extracting heavy metals. Compared with each inorganic acid, As removal from soil by washing agents increased in the order of sulfuric acid (35.81%) < phosphoric acid (62.96%). Therefore, an enhanced mixture solution using sulfuric acid and phosphoric acid to simultaneously remove heavy metals and As from contaminated soils was investigated. Sulfuric acid at 0.6 M was adopted to combine with 0.6 M phosphoric acid to obtain the mixture solution (1:1) that was used to determine the effect for the simultaneous removal of both heavy metals and As from the contaminated soil. The removal efficiencies of As, Cu, Pb, and Zn were 70.5%, 79.6%, 80.1%, and 71.2%, respectively. The combination of sulfuric acid with phosphoric acid increased the overall As and heavy metal extraction efficiencies from the contaminated soil samples. With the combined effect of dissolving oxides and ion exchange under combined washings, the removal efficiencies of heavy metals and As were higher than those of single washings.

Mass-production and biomarker-based characterization of high-value Spirulina powder for nutritional supplements.

Mass-produced Spirulina powder was characterized based on biomarkers for quality assessment. Other Spirulina powder products for functional foods and animal feeds were used as controls. In this study, Spirulina platensis was mass-cultured in modified Spirulina medium using a dispersive two-ton scale reactor for 30 days. After processing, the Spirulina powder was evaluated using FE-SEM and XPS. In the extracts, chlorophylls were determined using TLC and Q-TOF. SDS-PAGE and DSC were used to analyze protein biomarkers and to monitor thermal stability. The powder presented a microscale distorted sphere. Zinc, iron and calcium were detected on the powder surface. In the extracts, chlorophylls-a, -b, and -c, allophycocyanin, and phycocyanin-C were detected. Despite the similar morphology of all Spirulina products, the mass-produced Spirulina powder showed prolonged protein stability in biochemical compositions. The results suggest that mass-produced Spirulina powder can be characterized using biomarker-based advanced techniques. This protocol can be extended to other microalgae.