Pyrohydrolytic determination of fluorine in coal: a chemometric approach.

Corrosion effects in thermal power plants and environmental impact cause an increase in demand for fluorine analysis in coal. Solid sample decomposition, organic and inorganic fluorine compounds, volatility of fluorine species are problems which deserve a special attention. The aim of this work was to optimize the pyrohydrolytic (Phy) determination of fluorine content in the lignite coal. The parameters of pyrohydrolysis were evaluated and optimized by two statistical methods: Plackett-Burman (PB) design and response surface methodology (RSM). The content of fluorine in the absorption solution was measured by fluoride ion-selective electrode. The limit of detection of the proposed method was 20 microg g(-1), with good recovery (95%) and relative standard deviation less than 5%. With such benefits as simplicity, precision, accuracy and economy, this method is highly suitable for routine analysis of coal.

Governing factors for motor oil removal from water with different sorption materials.

This paper has been focused on the sorbent efficiency for motor oil removal from water. Two types of sorbents were investigated: organic and inorganic. Natural wool fibers (NWFs) and recycled-wool-based nonwoven material (RWNM)) were tested as organic type of sorbents. Sepiolite, bentonite and zeolite have been chosen as representative inorganic sorbents. Sorption was carried out in batch sorption system. Efficiency of oil removal was determined by measuring the oil concentration before and after the sorption process. Extractive-gravimetric method and refractive index determination have been applied as analytical methods for determination of oil concentration in water. Governing factors for sorbent efficiency were proposed, analysed and compared. It was concluded that sorption process is mostly affected by mass of sorbent, sorption time, temperature and pH value of water. NWFs, which were the most efficient sorbent showed maximal efficiency and maximal sorption capacity: 0.1 g of NWFs after 10 min at 20 degrees C and pH 8.00 sorbed 3.3 g of motor oil from 300 mL of water polluted with 4.5 g of motor oil. Maximal efficiency for all sorbents investigated was reached after 30 min of sorption processes, it was 95.0% for NWF, 43.0% for NRWM, 20.7% for sepiolite, 19.6% for bentonite and 21.2% for zeolite. Physical adsorption onto all sorbents is a favorable process (sorption efficiency decrease with increasing temperature) while sorption onto bentonite and zeolite is a result of both physical adsorption and chemisorption (sorption efficiency increase with increasing temperature, up to 80 degrees C).

Efficiency of oil removal from real wastewater with different sorbent materials.

The aim of this paper was to investigate the efficiency of different sorbent materials for oil removal from wastewater. Two types of sorbents were investigated: organic (loose natural wool fibers (NWF) and recycled wool based nonwoven material (RWNM)) and inorganic (sepiolite). Sorption was carried out in continuous tubular contractor (initial oil concentration of 1511 mg/dm(3)) and batch tank (initial oil concentration of 5066 mg/dm(3)). Wool-based sorbents showed higher sorption capacity (5.56 g/g for NWF and 5.48 g/g for RWNM) compared to sepiolite (0.19 g/g) in case of sorption in batch tank. The study on sorption in continuous tubular contractor suggested that volume of oily wastewater strongly affected oil removal. The results indicated that the combination of extractive-gravimetric and FTIR spectrophotometric methods can be recommended for precise determination of oil concentration, being suitable as a controlling tool for oil detection.