Adsorptive removal of various phenols from water by South African coal fly ash

South African coal fly ash (SACFA) was used to effectively remove phenol, 2-nitrophenol and 4-nitrophenol from wastewater. The rate of adsorption follows first-order kinetics before attaining equilibrium with the sorption rate (Kad) obtained being the  highest for 4-nitrophenol (p-nitrophenol) (7.0 x 10.3/h), followed by phenol (1.2 x 10.3/h) and 2-nitrophenol (o-nitrophenol) (1.0 x 10.3/h). Batch studies were performed to evaluate the adsorption process, and it was found that the Freundlich isothermeffectively fits the experimental data for the adsorbates better than the Langmuir model, with the fly ash having the highest adsorption capacity of 6.51 X 10-2 mg/g for 4-nitrophenol, 6.00 x 10-2 mg/g for 2-nitrophenol and 6.31 x10-2 mg/g for phenol. The fly ash was found to adsorb 90.2% of phenol, 88.9% of 2-nitrophenol and 92.6% of 4-nitrophenol at an initialconcentration of 20 mg/.. The desorption studies suggested that the desorption of 4-nitrophenol was the most difficult of the three adsorbates to be desorbed. The desorption efficiency was 17.9% for phenol, 18.8% for 2-nitrophenol and 10.2% for 4-nitrophenol. This work proved that SACFA can be used as an efficient adsorbent material for removal of phenol from water and wastewater

Chloride-binding Effect of Blast Furnace Slag in Cement Pastes Containing Added Chlorides

Corrosion of rebar in concrete is commonly associated with, and to a large degree influenced by, the free chloride concentration in the pore water. It is standard industry practice to add various mineral admixtures such as pulverised fuel ash (PFA), or fly ash, ground granulated blast furnace slag (GGBS) and silica fume (SF), to concrete mixtures to increase the corrosion resistance of the reinforcement in the matrix and its subsequent design life span. Various investigations have reported on the effect of mineral admixtures and additions on chloride binding in cementitious matrices, and the current study contributes further to knowledge in this field. Unlike previous investigations, this study attempted to make a clear distinction between the contributions of the two components in a blended cement consisting of ordinary Portland cement (OPC) and ground blast furnace slag (BFS). These contributions of each component have been quantified. Relationships between the total amount of chloride bound, the level ofBFS additions, and the levels of initial chloride content present in the matrix were determined. It was found that the OPC/BFS blended cement with partial BFS replacements of up to 50% displayed a lower binding capacity than that of the OPC on its own. This observation was derived based on the assumption that the OPC and slag reactions were treated as competing and equivalent and did not take any potential time delays into account, nor the degree of cement hydration. The chloride-binding efficiency by the BFS is dependent on both the BFS partial replacement addition level as well as the initial amount of chloride present in the matrix. It is shown that both the OPC and BFS contribute to chloride binding in cement pastes, depending on the amount of BFS that replace the OPC component in the matrix.Keywords: Chloride binding, granulated blast furnace slag, pore solution, permeability, corrosio

The Corrosion Behaviour of WC-Co-Ru Alloys in Aggressive Chloride Media

Hardmetals possess excellent wear resistance, making them suitable alloys in several industrial applications. Mine waters with both dissolved chloride and sulphate salts can be severely corrosive and can limit the application of hardmetal tools in the mining industry. Ru additions to these alloys can refine and improve selected mechanical properties, but its influence on the corrosion resistance is unknown. A series of WC-Co-Ru alloys was evaluated in different chloride containing media to investigate their corrosion resistance. Standard electrochemical corrosion tests, chronoamperometric measurements, and surface analyses with Raman spectroscopy were conducted. An increasing amount of Ru improves the corrosion resistance of all the alloys. The effect is not as dramatic as that observed with stainless steels containing Ru in corrosive media. In both corrosive media Ru decreased the cathodic Tafel constant and has a retarding influence on the cathodic part of the corrosion reaction. Raman analyses indicated the presence of tungsten oxide, hydrated tungsten oxide compounds, and CoO and Co3O4 formed on the alloy surfaces during the corrosion process

Influence on the oxidative potential of a heavy-duty engine particle emission due to selective catalytic reduction system and biodiesel blend

Although the particulate matter (PM) emissions from biodiesel fuelled engines are acknowledged to be lower than those of fossil diesel, there is a concern on the impact of PM produced by biodiesel to human health. As the oxidative potential of PM has been suggested as trigger for adverse health effects, it was measured using the Electron Spin Resonance (OPESR) technique. Additionally, Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF) was employed to determine elemental concentration, and Raman Spectroscopy was used to describe the amorphous carbon character of the soot collected on exhaust PM from biodiesel blends fuelled test-bed engine, with and without Selective Catalytic Reduction (SCR). OPESR results showed higher oxidative potential per kWh of PMproduced from a blend of 20% soybean biodiesel and 80% ULSD (B20) engine compared with a blend of 5% soybean biodiesel and 95% ULSD (B5),whereas the SCR was able to reduce oxidative potential for each fuel. EDXRF data indicates a correlation of 0.99 between concentration of copper and oxidative potential. Raman Spectroscopy centered on the expected carbon peaks between 1100 cm−1 and 1600 cm−1 indicate lower molecular disorder for the B20 particulate matter, an indicative of a more graphitic carbon structure. The analytical techniques used in this study highlight the link between biodiesel engine exhaust and increased oxidative potential relative to biodiesel addition on fossil diesel combustion. The EDXRF analysis confirmed the prominent role of metals on free radical production. As a whole, these results suggest that 20% of biodiesel blends run without SCR may pose an increased health risk due to an increase in OH radical generatio

Potentiometric Determination of Free Chloride in Cement Paste – an Alternative Method for Low-Budget Laboratories

Corrosion of rebar in concrete is commonly associated with, and to a large degree influenced by, the free chloride concentration in the pore water. The amount of chloride in concrete is important because chloride can promote corrosion of steel reinforcement when moisture and oxygen are present. A potentiometric procedure that makes use of direct measurement with a chloride ion selective electrode has been developed to analyze free chloride in the pore water extracted from cement paste.16 The accuracy and reliability of this analytical technique has been checked against a certified reference material, Merck sodium chloride solution. Confidence levels (CL0.95), of 0.03 and relative standard deviations of 0.2 % for chloride were determined for ordinary Portland cement (OPC) chloride binding capacity.Keywords: OPC, free chloride, potentiometr