Acid cleaning, procedure

Although relatively uncommon, low BW pH may occur for a variety of reasons under online operating conditions, resulting in either general or localized low pH corrosion. Under offline conditions, low pH corrosion usually is simply a result of improper acid cleaning procedures. 

Inadequate acid cleaning procedures also may introduce traces of copper into the boiler (typically originally present as copper-containing deposits), which can plate out onto clean metal surfaces and cause localized, anodic area pitting corrosion. 

Acid cleaning procedure for larger industrial WT boilers 655... 

Traditional methods for in-service cleaning of calcium salts such as phosphate and sulfate (which are not particularly amenable to simple acid-cleaning procedures) have often employed EDTA or NTA chelant-based formulations, together with ingredients such as phosphonate and polyacrylate. 

It is well known that the extreme hydrophobic and anti-adhesive properties of PFA allow quick and simple acidic cleaning procedures to be adopted when preparing labware for trace analysis [4], On the other hand, preparing conventional quartz vessels for trace analysis requires considerably longer, more powerful and more costly cleaning methods (e.g., boiling or streaming for many hours with HNOs) [5],... 

The acid cleaning procedure removes oxides and other contaminants by immersion in a suitable acid solution, usually at room temperature. The type of cleaning agent selected will depend, in most cases, on the material to be cleaned. The following general guidelines can be used ... 

After 30 hours, the maximum and critical fermentation is underway and the pH must remain above 4.0 for optimal fermentation. However, accompanying bacterial contamination from various sources such as yeast contamination, improper cleaning procedures, slow yeast growth, or excessive temperatures can result in a pH below 4.0. The remaining amylase enzymes, referred to as secondary conversion agents, are inactivated and can no longer convert the dextrins to maltose. Under these circumstances, the fermentor pH continues to drop because of acid production of the bacteria, and the pH can drop to as low as 3.0. The obvious result is a low ethanol yield and quaUty deterioration. 

Pretreatment For most membrane applications, particularly for RO and NF, pretreatment of the feed is essential. If pretreatment is inadequate, success will be transient. For most applications, pretreatment is location specific. Well water is easier to treat than surface water and that is particularly true for sea wells. A reducing (anaerobic) environment is preferred. If heavy metals are present in the feed even in small amounts, they may catalyze membrane degradation. If surface sources are treated, chlorination followed by thorough dechlorination is required for high-performance membranes [Riley in Baker et al., op. cit., p. 5-29]. It is normal to adjust pH and add antisealants to prevent deposition of carbonates and siillates on the membrane. Iron can be a major problem, and equipment selection to avoid iron contamination is required. Freshly precipitated iron oxide fouls membranes and reqiiires an expensive cleaning procedure to remove. Humic acid is another foulant, and if it is present, conventional flocculation and filtration are normally used to remove it. The same treatment is appropriate for other colloidal materials. Ultrafiltration or microfiltration are excellent pretreatments, but in general they are... 

Lead alloys Preferably use the electrolytic cleaning procedure just described. Alternatively, immerse for 5 min in boiling 1% acetic acid. Rinse in water to remove the acid and brush very gently with a soft bristle brush to remove any loosened matter. 

Iron and steel Preferably use the electrolytic cleaning procedure, or else immerse in Clark s solution (hydrochloric acid 1(X) parts, antimonious oxide... 

P 17] In order to have a catalyst with a sufficiently high specific surface area, pretreatment of the micro channels made of aluminum was necessary [17], Following a cleaning procedure, an oxide layer with a regular system of nanopores was generated by anodic oxidation (1.5% oxalic acid 25 °C 50 V DC 2 h exposure using an aluminum plate cathode followed by calcination). 

First, following a cleaning procedure, electrochemical deposition was carried out using an aqueous solution with PdS04 electrolyte, citric add, and boric acid (25 °C ... 

Carr et al. [2004] studied the incidence of different cleaning procedures on wool. ToF-SIMS analyses performed on the commercially scoured wool (negative ion mode) showed the presence of 18-methyleicosanoic acid thioester species (m/z 341), attributed to the presence of 18-methyleicosanoic acid (18-MEA) which is normally the predominant compound of the surface layer of wool. Other lipids are also detected. After artificial sunlight exposure, analyses show that 18-MEA disappears from the surface. 

A similar study has been performed on silk [Howell et al. 2007]. The ToF-SIMS fingerprint of silk exhibits the presence of different amino acid fragments (positive ion mode). In contrast to wool, the effect of artificial ageing is not obvious and no modification appears in the ToF-SIMS spectra. Nevertheless, the study of the cleaning procedures leads to the same conclusion as that in the case of wool. The amount of remaining surfactant increases with artificial ageing. 

Several key issues have to be addressed in the downstream processing of biopharmaceuticals regardless of the expression system. The removal of host cell proteins and nucleic acids, as well as other product- or process-related or adventitious contaminants, is laid down in the regulations and will not differ between the individual expression hosts. The identity, activity and stability of the end product has to be demonstrated regardless of the production system. The need for pharmaceutical quality assurance, validation of processes, analytical methods and cleaning procedures are essentially the same. 

The first aim of this work was to study the influence of an unwashed membrane filter on the cadmium, lead, and copper concentrations of filtered seawater samples. It was also desirable to ascertain whether, after passage of a reasonable quantity of water, the filter itself could be assumed to be clean so that subsequent portions of filtrate would be uncontaminated. If this were the case, it should be possible to eliminate the cleaning procedure and its contamination risks. The second purpose of the work was to test the possibility of long-term storage of samples at their natural pH (about 8) at 4 °C, kept in low-density polyethylene containers which have been cleaned with acid and conditioned with seawater. 

Flush the system to remove dust and major debris. Recirculate detergent or alkali cleaner at elevated temperatures to remove grease or oil. Flush and recirculate an acid at elevated temperatures to dissolve any ferrous particles in the system. Flush with water of the same quality as will be used in service. The cleaning procedure shall be validated by making chemical analysis of surface residues. System functional checkout... 

Recommended Solvent Selection Procedure. Resin contaminants have been identified only recently. Until 1977, only the following resin contaminants were identified naphthalene, ethylbenzene, and benzoic acid (36). The resin cleaning procedure of Junk et al. (5), which uses a series of three solvents of decreasing polarity, removes the widest possible variety of organic contaminants from the resins. This method is necessary when many compounds must be removed. 

Alkaline-cleaned substrate. After alkaline cleaning, the steel substrate was completely devoid of aliphatic fatty acids, as was verified by TOFSIMS. The freshly cleaned substrate was immediately immersed in the 1% silane solution and analyzed. The wettability of the cleaned steel by the solution was considerably improved by the alkaline cleaning procedure. The spectra obtained with a film deposited from a pH 10.5 solution are shown in Fig. 7. A rigorous peak identification procedure was applied here. The masses of all major peaks could be... 

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