Corrosion Behavior of Super Austenitic Stainless Steel 904L Weldment in Sulfuric Acid Media Used for Leaching Application

This article reports the corrosion behavior of 904L weldment in sulfuric acid as a strong corrosive media. The corrosion behavior was studied by total immersion tests and potentidynamic polarization test. Total immersion test has been conducted at different acid concentrations typically: 1, 2, 4, 6, 8 and 18.4 M at 25°C. The effect of temperature (25- 100°C) on the weight loss measurements of the alloy samples was followed in the 4 M acid solution. On the other hand, potentiodynamic polarization tests were conducted in 2,5, 8 and 18.4 M H2SO4 solution. The potentiodynamic polarization test was also conducted in the practically used leaching medium (2 M H2SO4 + 10% monazite).Results show that the weight loss increases with the increase of acid concentration and reaches its maximum at 4 M H2SO4 and then gradually decreases. Meanwhile, the rise in temperatures results in the increase of weight loss. Potentiodynamic polarization tests indicate that the 5 M acid solution gives the highest corrosion rate of 0.6399 mm/Y. The leaching medium shows relatively higher corrosion rate (0.124 mm/y) than the corresponding 2 M H2SO4 without monazite (0.01712 mm/y).

Leachability of Metal Ions in TCLP Leachate of Solidified Petroleum Sludge

Toxicity characteristic leaching procedure was executed on solidified petroleum sludge to investigate the metal ions release in leaching medium extractant fluid number 2, U.S.EPA SW-846 TCLP. Nine metal ions from solidified sludge in ordinary Portland cement were evaluated at water to cement ratio of 0.4 to 0.5 and incorporation of 5-15% cement replacement materials. Five cement replacement materials namely, rice husk ash, condense silica fume, activated carbon, fly ash and meta kaolin were selected for solidified sludge in the cement. Solidified sludge with cement replacement materials indicates minimum leachability of metal ions.

Potassium Extraction from Biotite by Penicillium and Aspergillus

Owing to lack of soluble potassium resource in some countries, it will be the competitive alternative to obtain potassium from insoluble K-bearing minerals (e.g. K-feldspar, biotite) in order to satisfy the requirements of potassium fertilizers for the agricultural sustainable development. In this work, seven fungal species including Penicillium oxalicum, P. ochrochloron, P. simplicissimum, P. spinulosum, Aspergillus niger, A. fumigatus, and A. oryzae were investigated for potassium extraction from biotite (9.64% K2O, weight fraction). Experiments were carried out in a shaker (30 °C, 180 rpm) with biotite directly dispersed in the leaching medium or enclosed in a dialysis bag. The concentrations of potassium, silicon and aluminum in the bioleaching solution were measured by Inductive Coupled Plasma (ICP), and K release amounts of biotite by seven fungal species were compared. It was found that all the strains had the abilities to enhance the dissolution of biotite, and P. oxalicum showed the highest K release amount among seven tested strains. Furthermore, the metabolites of fungi in the bioleaching process were analyzed by high performance liquid chromatography (HPLC), and the surface morphologies of biotite before and after bioleaching were characterized by Scanning Electron Microscope (SEM). The mechanism of microbial release of potassium from biotite by Penicillium andAspergillus was discussed.

Effect of Leaching Conditions on Dissolution Rate of Potassium from K-Feldspar Calcined Sample

Potassium feldspar, phosphogypsum and coke are used as raw materials to obtain soluble salts of calcined sample through mechanical grinding, roasting activation and leaching with acid. A study has been conducted on the factors that affect the leaching ratio of K2O of calcined samples, such as the type and concentration of leaching medium, temperature, time, liquid-solid ratio. The experiments show under the conditions that concentration of citric acid of 2% (wt%), liquid-solid ratio of 4, leaching for 4 hours at room temperature, potassium dissolution rate can reach 76.81%.

Pressure Evolution of a Bituminized Washing Water Concentrate During Leaching

In this investigation the swelling pressure of confined samples of a real waste form, consisting of bitumen containing washing water concentrate, was measured. The theoretically reachable swelling pressure was estimated as high as ∼ 273 bar (27 MPa).A first simple experimental set-up was a sample of bituminized radwaste embedded in a cylinder of sintered bronze with a piezo-resistive pressure transducer. This was put into a leaching medium. A maximum pressure of 2 bar (0.2 MPa) was measured. The leaching rates of these confined samples were similar to those of unconfined ones.The second set-up was a sample of bituminized radwaste embedded in a cylinder of stainless steel, also equipped with a pressure transducer. The open bottom of the cylinder was closed with a disc of porous cement with water/cement ratio of 1.3. In two similar experiments with this set-up the swelling pressure reached in one case a value of 9 bar = 0.9 MPa and in the second improved one about 15 bar = 1.5 MPa.