Investigation of transient forms of sulfur during biological treatment of spent caustic.

In the present study, the production of various transient forms of sulfur during biological oxidation of sulfidic spent caustics under haloalkaline conditions in a stirred tank bioreactor is investigated. Also, the effects of abiotic aeration (chemical oxidation), dissolved oxygen (DO) concentration and sodium concentration on forms of sulfur during biological treatment are demonstrated. Thioalkalivibrio versutus strain was used for sulfide oxidation in spent caustic (SC). The aeration had an important effect on sulfide oxidation and its final products. At DO concentrations above 2 mg l-1, majority of sulfide was oxidized to sulfate. Maximum sulfide removal efficiency (%R) and yield of sulfate production [Formula: see text] was obtained in Na+ concentration ranging from 0.6 to 2 M. Abiotic aeration, which is the most important factor of production of thiosulfate, resulted in the formation of an undesired product-polysulfide. However, abiotic aeration can be used as a pretreatment to biological treatment. In the bioreactor the removal efficiency was obtained as 82.7% and various forms of sulfur such as polysulfide, biosulfur, thiosulfate and sulfate was observed during biological treatment of SC.

The economic pre-treatment of coal mine drainage water with caustic and ozone.

Coal mine drainage waters are low in pH with varying amounts of iron and manganese and are generally brackish. The Austar Coal Mine in NSW, Australia, sought alternatives to their current lime dosing as the pre-treatment before the downstream reverse osmosis plant. Undesirable operating aspects of the current system include manganese and gypsum scaling/fouling, the need for anti-scalants and reduced water recovery. Thirteen processes for acid mine drainage were initially considered. The preferred process of caustic and ozone for Mn(II) oxidation was pilot tested at up to 0.74 kL/hr at the mine site. Under proper conditions and no aeration, about 81 per cent of the Fe could be removed (initially at 156 mg/L) as green rust. Supplemental aeration followed first-order kinetics and allowed 99.9 per cent Fe(II) oxidation and removal but only with a hydraulic residence time of about 47 minutes. The addition of supplemental Cu catalyst improved Fe removal. Ozone applied after caustic was effective in stoichiometrically oxidising recalcitrant Mn(II) and any remaining Fe(II). Control of the ozonation was achieved using the oxidation reduction potential during oxidation of the Mn(II) species. The use of caustic, followed by ozone, proved economically comparable to the current lime pre-treatment.

[Ingestion of caustic substances in children: 3 years of experience]. / Ingesta de cáusticos en niños, experiencia de 3 años.

INTRODUCTION: There is no clear consensus on the management of accidental ingestion of caustic substances in paediatrics. The aim of this study was to determine the profile of the paediatric population treated due to caustic ingestion in a Healthcare Centre. PATIENTS AND METHOD: A descriptive study was conducted on patients treated for the ingestion of caustic substances in our hospital during the period 2008-2011. RESULTS: A total of 12 patients were treated, with a mean age of 3.8 years (1-13 years), with the majority males (58.8%). An alkaline product was ingested by 58.3%, and an acid by 41.6%. The majority (58.3%) did not refer to symptoms and the remainder referred to vomiting (33.3%), odynophagia (16.6%), haematemesis (8.3%), hyper-salivation (8.3%) and shortness of breath (8.3%). Oral cavity lesions were observed in 75% of cases. All, except one, were accidental. An endoscopy was performed on all of them (100%) between 12 and 24hours post-ingestion, with pathological findings in 41.6%. In the group that ingested an alkali, 2 (16.6%) patients had lesions, one a grade 2B and one a grade 3 oesophagitis. In the acid ingestion group, 4 (33.3%) patients had lesions; one grade 1-2A oesophagitis, two acute non-erosive gastritis, and one acute haemorrhagic gastritis. A follow-up endoscopy was performed depending on the previous endoscopic findings. Only two patients presented with complications. CONCLUSIONS: Emphasis is placed on the endoscopic evaluation in the first 24hours of deliberate asymptomatic ingestions, as well as a strict follow-up in those that ingested acids, due to delayed associated lesions.

Experimental study of Lucilia sericata (Diptera Calliphoridae) larval development on rat cadavers: Effects of climate and chemical contamination.

Household products such as bleach, gasoline or hydrochloric acid have been used to mask the presence of a cadaver or to prevent the colonization of insects. These types of chemicals affect insect development and alter the forensic entomology analysis. This study was designed to test the effects of six household products (bleach, mosquito repellent, perfume, caustic soda, insecticide and unleaded gasoline) on blowfly (Lucilia sericata, Diptera: Calliphoridae) larval development. Furthermore, the effects of climate (rain or dry conditions) on larval development were analyzed. For each replication, 100 first instars were placed on a rat cadaver on which one household product was spilled. We observed a decrease in the survival rates of the larvae but no significant effect on their development times or the adult size. The same trends were observed under rainy conditions. However, the rain altered the effects of some tested household products, especially gasoline. These results demonstrate for the first time the successful development of necrophagous larvae on chemically contaminated cadavers, and provide evidence for the range of possible effects to expect.

Ingesta de cáusticos en niños, experiencia de 3 años / Ingestion of caustic substances in children: 3 years of experience

Introdución: La ingesta accidental de cáusticos en pediatría no dispone de un consenso claro de actuación. El objetivo de este estudio fue caracterizar la población pediátrica atendida por ingesta de cáusticos en un centro asistencial. Pacientes y método: Estudio descriptivo de los pacientes atendidos en nuestro hospital por la ingesta de cáusticos durante el período 2008-2011. Resultados: Se atendieron 12 pacientes, edad media de 3,8 años (1-13 años). Predominio de varones (58,8%). Un 58,3% ingirió producto alcalino y un 41,6% ácido. El 58,3% no refería sintomatología, el resto refirió vómitos (33,3%), odinofagia (16,6%), hematemesis (8,3%), sialorrea (8,3%) y dificultad respiratoria (8,3%). El 75% presentaron lesiones en la cavidad oral. Todos, salvo un caso, fueron accidentales. Se realizó endoscopia al 100% entre las 12 y 24 h postingesta con hallazgos patológicos en un 41,6%. En el grupo ingesta de álcalis 2 pacientes presentaron lesiones (16,6%): una esofagitis grado 2B y una grado 3. En el grupo ingesta de ácidos 4 pacientes (33,3%) presentaron lesiones: una esofagitis aguda grado 1-2A, 2 gastritis agudas no erosivas y una gastritis aguda hemorrágica. Se realizó endoscopia de control según los hallazgos endoscópicos previos. Solo 2 presentaron complicaciones posteriores. Conclusiones: Destacamos la valoración endoscópica en las primeras 24 h en todas las ingestas sintomáticas y deliberadas, así como la reevaluación estrecha en las ingestas ácidas, por asociar lesiones diferidas.

Introduction: There is no clear consensus on the management of accidental ingestion of caustic substances in paediatrics. The aim of this study was to determine the profile of the paediatric population treated due to caustic ingestion in a Healthcare Centre. Patients and method: A descriptive study was conducted on patients treated for the ingestion of caustic substances in our hospital during the period 2008-2011. Results: A total of 12 patients were treated, with a mean age of 3.8 years (1-13 years), with the majority males (58.8%). An alkaline product was ingested by 58.3%, and an acid by 41.6%. The majority (58.3%) did not refer to symptoms and the remainder referred to vomiting (33.3%), odynophagia (16.6%), haematemesis (8.3%), hyper-salivation (8.3%) and shortness of breath (8.3%). Oral cavity lesions were observed in 75% of cases. All, except one, were accidental. An endoscopy was performed on all of them (100%) between 12 and 24 hours post-ingestion, with pathological findings in 41.6%. In the group that ingested an alkali, 2 (16.6%) patients had lesions, one a grade 2B and one a grade 3 oesophagitis. In the acid ingestion group, 4 (33.3%) patients had lesions; one grade 1-2A oesophagitis, two acute non-erosive gastritis, and one acute haemorrhagic gastritis. A follow-up endoscopy was performed depending on the previous endoscopic findings. Only two patients presented with complications. Conclusions: Emphasis is placed on the endoscopic evaluation in the first 24 hours of deliberate asymptomatic ingestions, as well as a strict follow-up in those that ingested acids, due to delayed associated lesions.

Surface chemical immobilization of bioactive peptides on synthetic polymers for cardiac tissue engineering.

The aim of this work was the development of new synthetic polymeric systems, functionalized by surface chemical modification with bioactive peptides, for myocardial tissue engineering. Polycaprolactone and a poly(ester-ether-ester) block copolymer synthesized in our lab, polycaprolactone-poly(ethylene oxide)-polycaprolactone (PCL-PEO-PCL), were used as the substrates to be modified. Two pentapeptides, H-Gly-Arg-Gly-Asp-Ser-OH (GRGDS) from fibronectin and H-Tyr-Ile-Gly-Ser-Arg-OH (YIGSR) from laminin, were used for the functionalization. Polymeric membranes were obtained by casting from solutions and then functionalized by means of alkaline hydrolysis and subsequent coupling of the bioactive molecules through 1-(3-dimethylaminopropyl)-3-ethylcarbodimide hydrochloride/N-hydroxysuccinimide chemistry. The hydrolysis conditions, in terms of hydrolysis time, temperature, and sodium hydroxide concentration, were optimized for the two materials. The occurrence of the coupling reaction was demonstrated by infrared spectroscopy, as the presence on the functionalized materials of the absorption peaks typical of the two peptides. The peptide surface density was determined by chromatographic analysis and the distribution was studied by infrared chemical imaging. The results showed a nearly homogeneous peptide distribution, with a density above the minimum value necessary to promote cell adhesion. Preliminary in vitro cell culture studies demonstrated that the introduction of the bioactive molecules had a positive effect on improving C2C12 myoblasts growth on the synthetic materials.

A comparative study of the treatment of ethylene plant spent caustic by neutralization and classical and advanced oxidation.

The treatment of spent caustic produced from an ethylene plant was investigated. In the case of neutralization alone it was found that the maximum removal of sulfide was at pH values below 5.5. The higher percentage removal of sulfides (99% at pH = 1.5) was accompanied with the highest COD removal (88%). For classical oxidation using H2O2 the maximum COD removal percentage reached 89% at pH = 2.5 and at a hydrogen peroxide concentration of 19 mM/L. For the advanced oxidation using Fenton's process it was found that the maximum COD removal of 96.5% was achieved at a hydrogen peroxide/ferrous sulfate ratio of (7:1).

Quantitation of sugar content in pyrolysis liquids after acid hydrolysis using high-performance liquid chromatography without neutralization.

A rapid method for the quantitation of total sugars in pyrolysis liquids using high-performance liquid chromatography (HPLC) was developed. The method avoids the tedious and time-consuming sample preparation required by current analytical methods. It is possible to directly analyze hydrolyzed pyrolysis liquids, bypassing the neutralization step usually required in determination of total sugars. A comparison with traditional methods was used to determine the validity of the results. The calibration curve coefficient of determination on all standard compounds was >0.999 using a refractive index detector. The relative standard deviation for the new method was 1.13%. The spiked sugar recoveries on the pyrolysis liquid samples were between 104 and 105%. The research demonstrates that it is possible to obtain excellent accuracy and efficiency using HPLC to quantitate glucose after acid hydrolysis of polymeric and oligomeric sugars found in fast pyrolysis bio-oils without neutralization.

Structural elucidation of sorghum lignins from an integrated biorefinery process based on hydrothermal and alkaline treatments.

An integrated process based on hydrothermal pretreatment (HTP) (i.e., 110-230 °C, 0.5-2.0 h) and alkaline post-treatment (2% NaOH at 90 °C for 2.0 h) has been performed for the production of xylooligosaccharide, lignin, and digestible substrate from sweet sorghum stems. The yield, purity, dissociation mechanisms, structural features, and structural transformations of alkali lignins obtained from the integrated process were investigated. It was found that the HTP process facilitated the subsequent alkaline delignification, releasing lignin with the highest yield (79.3%) and purity from the HTP residue obtained at 190 °C for 0.5 h. All of the results indicated that the cleavage of the ß-O-4 linkages and degradation of ß-ß and ß-5 linkages occurred under the harsh HTP conditions. Depolymerization and condensation reactions simultaneously occurred at higher temperatures (≥ 170 °C). Moreover, the thermostability of lignin was positively related to its molecular weight, but was also affected by the inherent structures, such as ß-O-4 linkages and condensed units. These findings will enhance the understanding of structural transformations of the lignins during the integrated process and maximize the potential utilizations of the lignins in a current biorefinery process.

Effect of alkali and oxidative treatments on the physicochemical, pasting, thermal and morphological properties of corn starch.

BACKGROUND: Few studies on starch modifications using different chemical agents are available in the literature, and no reports were found on the combined effect of oxidation and alkaline treatment of corn starch. Thus this work evaluated the physicochemical, pasting, morphological, cystallinity and thermal properties of chemically modified corn starch, after either the isolated or combined action of alkaline (sodium hydroxide) and oxidative (sodium hypochlorite) treatments. RESULTS: The highest values for the sum of carbonyl and carboxyl and enzymatic hydrolysis occurred in starches submitted to oxidative treatment at high active chlorine concentrations. The alkali treatment in isolation modified the pasting properties, reduced the paste temperature and increased the peak viscosity, breakdown, final viscosity and setback of starches. Starch modified by the action of sodium hypochlorite and hydroxide in combination presented more severe damage on granule surfaces. CONCLUSION: The results show that corn starch modified by the combined action of oxidative and alkaline treatments should be studied more, especially at the concentration limit of sodium hydroxide where gelatinization occurs. Under these conditions the effect of oxidation can be more intense and thus allow the production of starches with different properties and an increase in their industrial applications.

Suicide by hydrogen sulfide inhalation.

The authors report a case of suicide by hydrogen sulfide in Australia. A young woman was located in a car wearing protective eyewear. A tub of foamy yellow substance and a quantity of hydrochloric acid and lime sulfur were also located in the rear of the vehicle. Morphological findings at autopsy were nonspecific. Toxicologic analysis of a specimen of leg blood detected elevated levels of methemoglobin. If Australia follows a similar trend to Japan and the United States, it is possible that incidences of such cases will rise, probably because of Internet dissemination. From a public health perspective, emergency service providers and forensic case workers should be aware of the potential hazards to themselves and others when dealing with such cases.

Properties of dental resins submitted to pH catalysed hydrolysis.

OBJECTIVES: This study evaluated the surface microhardness (SM) and roughness (SR) alterations of dental resins submitted to pH catalysed degradation regimens. METHODS: Thirty discs of each TPH Spectrum (Dentsply), Z100 (3M-ESPE), or an unfilled experimental bis-GMA/TEGDMA resin were fabricated, totaling 90 specimens. Each specimen was polymerized for 40 s, finished, polished, and individually stored in deionized water at 37 °C for 7 days. Specimens were randomly assigned to the following pH solutions: 1.0, 6.9 or 13, and for SM or SR evaluations (n = 5). Baseline Knoop-hardness of each specimen was obtained by the arithmetic mean of five random micro-indentations. For SR, mean baseline values were obtained by five random surface tracings (R(a)). Specimens were then soaked in one of the following storage media at 37 °C: (1) 0.1 M, pH 1.0 HCl, (2) 0.1 N, pH 13.0 NaOCl, and (3) deionized water (pH 6.9). Solutions were replaced daily. Repeated SM and SR measurements were performed at the 3-, 7- and 14-day storage time intervals. For each test and resin, data were analysed by two-way ANOVA followed by Tukey's test (α = 0.05). RESULTS: There was significant decrease in SM and increase in SR values of composites after storage in alkaline medium. TPH and Z100 presented similar behaviour for SM and SR after immersion in the different media, whereas unfilled resin values showed no significant change. CONCLUSION: Hydrolytic degradation of resin composites seems to begin with the silanized inorganic particles and therefore depend on their composition. SIGNIFICANCE: To accelerate composite hydrolysis and produce quick in vitro microstructural damage, alkaline medium appears to be more suitable than acidic medium. Contemporary resin composite properties seem to withstand neutral and acidic oral environments tolerably well.

pH-responsive nanovalves based on hollow mesoporous silica spheres for controlled release of corrosion inhibitor.

In the present study, a new encapsulation technique for corrosion inhibitor is proposed. The hollow mesoporous silica spheres (HMSs) were synthesized by the co-templates method as nanocontainers for corrosion inhibitor, benzotriazole (BTA) and the supramolecular nanovalves, consisting of cucurbit[6]uril (CB[6]) rings and the functional stalks attached to the surface of HMSs achieved on-demand release. The synthesis process of HMSs and the assembly process of the nanovalves were confirmed by SEM, TEM, N(2) adsorption/desorption, FTIR, TGA and solid-state (13)C CP/MAS NMR. The encapsulation capacity and release characteristics of BTA-loaded, assembled HMSs were investigated. The HMSs assembled with the nanovalves possessed a higher encapsulation capacity for BTA than MCM-41 assembled under the same procedure due to its huge hollow internal structure. The pH-controlled release properties of BTA from the assembled HMSs under different pH environments were monitored by ultraviolet absorption spectra. The release profiles showed that there was almost no leakage of BTA from the assembled HMSs in neutral solution, while in alkaline solution BTA released very quickly, and the release rate increased with increasing pH values. Such a property makes the HMSs assembled with the pH-responsive nanovalves have great potential applications in smart anticorrosion coatings.

Influence of blood contamination before or after surface treatment on adhesion of 4-META/MMA-TBB resin to root dentin.

The purpose of this study was to evaluate the influence of blood contamination before or after surface treatment on adhesion of 4-META/MMA-TBB resin. After bovine root dentin surfaces were contaminated with blood before or after dentin surface treatment with 10-3 solution, the contaminated surface was rinsed with water, air-dried, or re-treated with 10-3 solution. Dye leakage and microtensile bond strength (MTBS) of 4-META/MMA-TBB resin to dentin were measured after storage in water for 24 h. When blood contamination occurred before surface treatment, there was no significant difference in the leakage value and MTBS as compared with that of the uncontaminated group. When blood contamination occurred after surface treatment, the leakage value increased and MTBS significantly decreased (p<0.05) even if the blood was washed away. However, when the surface was re-treated with 10-3 solution after rinsing with water, the leakage value and MTBS were restored to those of the uncontaminated group.

Stabilizing sodium hypochlorite at high pH: effects on soft tissue and dentin.

INTRODUCTION: When sodium hypochlorite solutions react with tissue, their pH drops and tissue sorption decreases. We studied whether stabilizing a NaOCl solution at a high pH would increase its soft-tissue dissolution capacity and effects on the dentin matrix compared with a standard NaOCl solution of the same concentration and similar initial pH. METHODS: NaOCl solutions were prepared by mixing (1:1) a 10% stock solution with water (standard) or 2 mol/L NaOH (stabilized). Physiological saline and 1 mol/L NaOH served as the controls. Chlorine content and alkaline capacity of NaOCl solutions were determined. Standardized porcine palatal soft-tissue specimens and human root dentin bars were exposed to test and control solutions. Weight loss percentage was assessed in the soft-tissue dissolution assay. Three-point bending tests were performed on the root dentin bars to determine the modulus of elasticity and flexural strength. Values between groups were compared using one-way analysis of variance with the Bonferroni correction for multiple testing (α < .05). RESULTS: Both solutions contained 5% NaOCl. One milliliter of the standard and the stabilized solution consumed 4.0 mL and 13.7 mL of a 0.1-mol/L HCl solution before they reached a pH level of 7.5, respectively. The stabilized NaOCl dissolved significantly more soft tissue than the standard solution, and the pH remained high. It also caused a higher loss in elastic modulus and flexure strength (P < .05) than the control solutions, whereas the standard solution did not. CONCLUSIONS: NaOH-stabilized NaOCl solutions have a higher alkaline capacity and are thus more proteolytic than standard counterparts.

The effects of corrosive substances on human bone, teeth, hair, nails, and soft tissue.

This research investigates the effects of household chemicals on human tissues. Five different human tissues (bone, tooth, hair, fingernails, and skin/muscle/fat) were immersed into six different corrosive agents. These agents consisted of hydrochloric acid, sulfuric acid, lye, bleach, organic septic cleaner, and Coca-Cola(®) soda. Tap water was used as a control. Tissue samples were cut to consistent sizes and submerged in the corrosive liquids. Over time, the appearance, consistency, and weight were documented. Hydrochloric acid was the most destructive agent in this study, consuming most tissues within 24 h. Sulfuric acid was the second most destructive agent in this study. Bleach, lye, and cola had no structural effects on the hard tissues of the body, but did alter the appearance or integrity of the hair, nails, or flesh in some way. The organic septic cleaner and tap water had no effect on any of the human tissue tested during the timeframe of the study.

Characteristics of nitrogen removal and microbial distribution by application of spent sulfidic caustic in pilot scale wastewater treatment plant.

Since spent sulfidic caustic (SSC) produced from petrochemical industry contains a high concentration of alkalinity and sulfide, it was expected that SSC could be used as an electron donor for autotrophic denitrification. To investigate the nitrogen removal performance, a pilot scale Bardenpho process was operated. The total nitrogen removal efficiency increased as SSC dosage increased, and the highest efficiency was observed as 77.5% when SSC was injected into both anoxic tank (1) and (2). FISH analysis was also performed to shed light on the effect of SSC dosage on the distribution ratio of nitrifying bacteria and Thiobacillus denitrificans. FISH results indicated that the relative distribution ratio of ammonia-oxidizing bacteria, Nitrobacter spp., Nitrospira genus and Thiobacillus denitrificans to eubacteria varied little with the pH of the tanks, and SSC injection did not give harmful effect on nitrification efficiency. These results show that SSC can be applied as an electron donor of autotrophic denitrification to biological nitrogen removal process effectively, without any inhibitory effects to nitrifying bacteria and sulfur-utilizing denitrifying bacteria.