Selecting and improving activated homogeneous catalytic processes for pollutant removal. Kinetics, mineralization and optimization

The degradation of a model pollutant, tartrazine, very used in food industry and usually present in WWTPs effluents and surface waters, was investigated by nine activated homogeneous catalytic processes, namely, Fe³⁺/H₂O₂, Fe²⁺/H₂O₂, UV/H₂O₂, UV/S₂O₈^2-, UV/Fe²⁺/H₂O₂, UV/Fe³⁺/H₂O₂, UV, VIS/Fe³⁺/H₂O₂, and VIS/Fe³⁺/H₂O₂/C₂O₄^2-. In order to compare the mineralization and oxidation ability of each process, the removal of dye, chemical oxygen demand (COD) and total organic carbon (TOC) were analyzed, as well as the overall kinetic rate constant. Also, the different oxidation path-ways (direct photolysis and/or oxidation by free radicals) were estimated for each system. After the comparison, the Fenton process, which had the highest mineralization values, was tested in luminous and dark phases using designed experiments, and the influences of all operating variables were studied by RSM.

Serum calcium (S-Ca), the forgotten test: preliminary results of an appropriateness strategy to detect primary hyperparathyroidism (pHPT)

BACKGROUND

With the introduction of automated calcium measurements with multichannel continuous-flow analyzers in the 1970s, primary hyperparathyroidism (pHPT), the silent disease, began to be detected. Years later, with the first appearance of random access analyzers, laboratory tests were requested if the patient had clinical symptoms and pHPT was again overlooked. In this current scenario, serum calcium (s-Ca) is at risk of becoming a forgotten test. In consensus with endocrinologists and general practitioners (GPs), we implemented a strategy to detect asymptomatic pHPT patients.

METHODS

During a 9 month period, the Laboratory Information System automatically added s-Ca to every sample of blood from primary care patients older than 45 years, without a s-Ca request in the previous three years. If hypercalcemia was detected (albumin-corrected s-Ca > 2.6 mmol/L), phosphate, 25-hydroxy vitamin D and parathyroid hormone (PTH) were automatically processed in the same sample. We reviewed the medical record of every patient with hypercalcemia.

RESULTS

S-Ca was automatically added to 14,461 samples, with 79 hypercalcemia results. 14 hypercalcemia results with PTH levels in the reference range were clinically justified by causes other than pHPT. Of the remaining 65 patients, 41 were referred for evaluation by endocrinology. 34 resulted in a diagnosis of pHPT and 7 are currently in study. 24 patients were not followed by GPs to find out the primary cause of hypercalcemia. After a phone call from the laboratory, they are also currently being studied for hypercalcemia. Each case represented a cost of 110.4 US dollars.

CONCLUSION

Our proposed opportunistic screening to discover pHPT seems cost-effective.

Degradation of wine distillery wastewaters by the combination of aerobic biological treatment with chemical oxidation by Fenton's reagent

The degradation of wine distillery wastewaters by aerobic biological treatment has been investigated in a batch reactor. The evolution of the chemical oxygen demand, biomass and total contents of polyphenolic and aromatic compounds was followed through each experiment. According to the Contois model, a kinetic expression for the substrate utilization rate is derived, and its biokinetic constant is evaluated. The final effluents of the aerobic biological experiments were oxidized by Fenton's reagent. The evolution of chemical oxygen demand, hydrogen peroxide concentration and total contents of polyphenolic and aromatic compounds was followed through each experiment. A kinetic model to interpret the experimental data is proposed. The kinetic rate constant of the global reaction is determined.

Physico-chemical treatment for the depuration of wine distillery wastewaters (vinasses)

In the present work, an integrated Fenton-coagulation/flocculation process was applied for the depuration of wine distillery wastewaters, commonly known as "vinasses". This study evaluates the Fenton process (H2O2/Fe2+), involving oxidation--in a first stage and coagulation/flocculation (using Ca(OH)2 as base-precipitant)--in a second stage for the removal of chemical oxygen demand (COD). The experimental variables studied were the dosages of hydrogen peroxide and iron salts, the molar ratio [H2O2]o: [Fe2+]o, the effluent dilution and the manner in which the reagents were added (splitting the reagent dose of hydrogen peroxide and ferrous salt into different fractions). The optimal operating conditions of the integrated process were: [H2O2]o = 0.5 mol/L using an optimal concentration ratio [H2O2]o: [Fe2+]o= 15 mol/mol. Under these conditions, the COD removal was 74%.

Kinetic model for phenolic compound oxidation by Fenton's reagent

A kinetic model is developed for the oxidation of phenolic compounds by Fenton's reagent. In the first stage a rigorous kinetic model is applied to calculate the different kinetic rate constants for the oxidation process of p-hydroxybenzoic acid. In a second phase a competitive method is applied to calculate these kinetic constants for another 10 phenolic compounds present in agroindustrial and pulp paper wastewaters. These 10 phenolic compounds were: beta-resorcylic acid, 3-(4-hydroxyphenyl)-propionic acid, ferulic acid, protocatechuic acid, caffeic acid, p-coumaric acid, vanillic acid, syringic acid, veratric acid and 3,4,5-trimethoxybenzoic acid.

Oxidation of p-hydroxybenzoic acid by UV radiation and by TiO2/UV radiation: comparison and modelling of reaction kinetic

The phenolic compound p-hydroxybenzoic acid is very common in a great variety of agroindustrial wastewaters (olive oil and table olive industries, distilleries). The objective of this work was to study the photocatalytic activity of TiO2 towards the decomposition of p-hydroxybenzoic acid. In order to demonstrate the greater oxidizing power of the photocatalytic system and to quantify the additional levels of degradation attained, we performed experiments on the oxidation of p-hydroxybenzoic acid by UV radiation alone and by the TiO2/UV radiation combination. A kinetic model is applied for the photooxidation by UV radiation and by the TiO(2)/UV system. Experimental results indicated that the kinetics for both oxidation processes can be fitted well by a pseudo-first-order kinetic model. The second oxidation process can be explained in terms of the Langmuir-Hinshelwood kinetic model. The values of the adsorption equilibrium constant, K(pHB), and the second order kinetic rate constant, k(c), were 0.37 ppm(-1) and 6.99 ppm min(-1), respectively. Finally, a comparison between the kinetic rate constants for two oxidation systems reveals that the constants for the TiO2/UV system are clearly greater (between 220-435%) than those obtained in the direct UV photooxidation.

Kinetics of the reaction between ozone and phenolic acids present in agro-industrial wastewaters

The kinetics of the ozonation of three phenolic acids is investigated from ozone absorption experiments in a semi-continuous reactor. After the evaluation of stoichiometric ratios for the individual reactions between ozone and each phenolic acid, the oxidation of p-hydroxybenzoic acid by ozone is performed in a first stage. The influence of the operating variables on the degradation process is established, and the application of a mass transfer with chemical reaction model based on the film theory leads to the determination of the reaction orders and kinetic rate constants. The experimental absorption rates obtained agree well with those calculated theoretically. In the second stage, a mixture of ferulic acid (4-hydroxy-3-methoxycinnamic acid), beta-resorcylic acid (2,4-dihydroxybenzoic acid) and p-hydroxybenzoic acid is ozonated under different experimental conditions. The kinetic study is performed by means of a competitive method that takes p-hydroxybenzoic acid as reference compound. The application of this model allows to determine the kinetic rate constants for each compound, which are correlated as a function of pH and temperature. The results obtained support that the kinetic regime of absorption is fast and pseudo-first order with respect to ozone, a condition required by the competitive method used.

Comparison of the degradation of p-hydroxybenzoic acid in aqueous solution by several oxidation processes

A comparative study is made of 12 methods of chemical oxidation applied to degrading p-hydroxybenzoic acid in aqueous solution. The oxidation processes tested were: UV, O3, UV/TiO2, O3/Fe2+, O3/H2O2, O3/UV, UV/H2O2, H2O2/Fe2+, H2O2/Fe2+/O3, UV/H2O2/O3, H2O2/Fe2+/UV and O3/UV/H2O2/Fe2+. The 12 processes were ranked by reactivity. In a kinetic study, the overall kinetic rate constant was split up into three components: direct oxidation by UV irradiation (photolysis), direct oxidation by ozone (ozonation), and oxidation by free radicals (mainly OH*).

Kinetics of p-hydroxybenzoic acid photodecomposition and ozonation in a batch reactor

The decomposition of p-hydroxybenzoic acid, an important pollutant present in the wastewaters of the olive oil industry, has been carried out by a direct photolysis provided by a polychromatic UV radiation source, and by ozone. In both processes, the conversions obtained as a function of the operating variables (temperature, pH and ozone partial pressure in the ozonation process) are reported. In order to evaluate the radiation flow rate absorbed by the solutions in the photochemical process, the Line Source Spherical Emission Model is used. The application of this model to the experimental results provides the determination of the reaction quantum yields which values ranged between 8.62 and 81.43 l/einstein. In the ozonation process, the film theory allows to establish that the absorption process takes place in the fast and pseudo-first-order regime and the reaction is overall second-order, first-order with respect to both reactants, ozone and p-hydroxybenzoic acid. The rate constants are evaluated and vary between 0.18x10(5) and 29.9x10(5) l/mol s depending on the temperature and pH.

A comparison of electrophysiological tests for the early diagnosis of diabetic neuropathy

Clinical criteria and several electrophysiological parameters for detecting nerve damage were compared in 99 patients with diabetes mellitus type 1 and type 2. Abnormal results were found in sural/radial amplitude ratio (51%), minimal F-wave latency of the tibial nerve (36.4%), sensory conduction velocity of the sural nerve (29.8%), and sural sensory nerve action potential amplitude (29.3%) when pooling data from all patients and comparing them to age- and height-matched normal control subjects. Analysis of all the parameters revealed large differences between the diabetes mellitus type 1 and type 2 groups, suggesting that the type of diabetes must be taken into account when comparing the sensitivity of nerve conduction tests. In diabetes mellitus type 1, the sural/radial ratio had the clearest correlation with course of illness and was the first parameter to show a significant reduction. We conclude that the simple ratio between sural and radial amplitudes is a very sensitive parameter and abnormalities in this ratio provide the means for earliest detection of neuropathy in diabetes mellitus type 1.

Influence of anti-insulin antibodies on insulin immunoassays in the autoimmune insulin syndrome

The autoimmune insulin syndrome (AIS) is a rare, benign syndrome characterized by hyperinsulinaemia and hypoglycaemia associated with the presence of autoantibodies to insulin in patients who have not been treated with insulin. We report here the case of a 52-year-old patient with recurrent attacks of severe postprandial hypoglycaemia and we also present the effect of anti-insulin antibodies on insulin immunoassays. The patient was submitted to the following diagnostic tests: 5-h oral glucose tolerance test (OGTT), a prolonged 72-h fast and an insulin tolerance test (ITT). Serum glucose, total and free insulin, C-peptide, proinsulin, insulin antibodies and other autoantibodies were measured. Insulin concentrations were measured by two methods: a double antibody radioimmunoassay (RIA) and an immunoradiometric assay (IRMA). Insulin concentration measured by RIA was extremely high in the OGTT and 72-h fast. In contrast, insulin concentrations measured by IRMA were between 120 and 888 pmol/L in the OGTT and between 37 and 133 pmol/L during the 72-h fast. Fasting free-insulin concentrations measured by RIA were between 2224 and 2669 pmol/L, whereas free-insulin concentrations measured by IRMA ranged between 93 and 237 pmol/L. Total insulin concentrations measured by RIA and IRMA were 57,615 and 94,021 pmol/L, respectively. The C-peptide concentrations were moderately high in the three tests. Serum insulin antibody concentrations were extremely high (62-71%), compared with less than 3% in normal serum samples. In conclusion, the high insulin concentrations measured by RIA were caused by insulin autoantibodies. However, insulin concentrations measured by IRMA were not influenced by them. We conclude that IRMA is the more accurate method for measuring insulin concentrations in such cases.

Usefulness of urinary growth hormone (GH) measurement for evaluating endogenous GH secretion in acromegaly

We investigated the relationship between urinary growth hormone (u-GH) and spontaneous 24-hour plasma GH secretion in 15 acromegalic patients. To measure u-GH, we have developed a method based on concentrating the sample by centrifugal ultrafiltration and then performing an immunoradiometric assay using commercially available reagents. u-GH correlated well with the integrated concentration of plasma GH (r = 0.66, p < 0.02). Additionally, u-GH excretion in acromegalic patients was significantly higher than in the control group (190 +/- 100 vs. 3.89 +/- 0.56 pg/min, mean +/- SEM, p < 0.001). Immunoreactive u-GH showed the same elution pattern in Sephadex G-75 as standard or labeled hGH, proving that the substance measured in urine is authentic GH. In conclusion, u-GH appears to be a simple, noninvasive and inexpensive test for evaluating GH secretion in active acromegaly.

Role of dopamine and vasoactive intestinal peptide in the control of pulsatile prolactin secretion

The present studies were designed to obtain a detailed characterization of pulsatile PRL secretory patterns under basal conditions and to explore the role of dopamine (DA) and vasoactive intestinal peptide (VIP) in the genesis of PRL pulses. Adult intact male rats received chronic indwelling jugular canula and were bled at 3-min intervals for periods ranging from 90-150 min. Pulse analysis was performed using the algorithm Detect. Blockade of DA receptors with domperidone, pimozide, or haloperidol resulted in a 2-fold increase in PRL pulse frequency, with no change in pulse duration. All quantitative parameters, i.e. peak and trough values, pulse amplitude, and area under the pulse, were significantly increased after dopaminergic blockade. Blockade of endogenous VIP activity was achieved by passive immunization with a potent VIP antiserum. This treatment, by itself, did not modify basal PRL levels or PRL pulsatility parameters. However, when VIP antiserum was administered in combination with domperidone, a reduction in all quantitative pulse parameters was observed. Heterogeneity of PRL pulses was evaluated by frequency distribution analysis, using the area under the pulse divided by basal secretion, to evaluate the mass of hormone secreted per pulse normalized to the basal rate of secretion. Untreated animals presented pulses within a range of different masses. Dopaminergic blockade resulted in a great reduction in big mass pulses, and the distribution of pulses was restricted primarily to small mass pulses. The increased pulse frequency after dopaminergic blockade, therefore, results mainly from an increase in the appearance of small mass pulses. These results indicate that DA exerts a tonic inhibitory action on the frequency as well as the qualitative parameters of PRL pulses. They also suggest that big mass PRL pulses are dopaminergic in origin, i.e. they may result from temporary interruptions in DA activity. Small mass PRL pulses appear to result from other neural stimulatory inputs. Endogenous VIP enhances quantitative PRL pulse parameters, but this activity is only apparent after removal of DA inhibition.

Distinct pulsatile prolactin secretory patterns during the estrous cycle: possible encoding for diverse physiological responses

PRL levels during the estrous cycle have been reported to be low, with the notable exception of the afternoon proestrous surge. The present study was designed to evaluate the pulsatile pattern of PRL secretion during the low secretory phases of the cycle. Animals were bled at 3-min intervals for 150 min during proestrus morning (AM), estrus AM and evening (PM), metestrus AM, and diestrus AM and PM. Using the algorithm Detect, pulse frequency, duration, interval, peak and trough values, area under the pulses, and mean PRL levels were calculated. PRL secretion was pulsatile during all stages of the estrous cycle, although the pattern varied considerably among the different cycle stages. Pulse frequency was highest during estrus and lowest during diestrus. All quantitative pulse parameters (peak, trough, amplitude, and area under pulse) were also higher during estrus and lowest in diestrus. Analysis of area under the pulse using frequency distribution indicated that at least two subpopulations of pulses, i.e. small mass and large mass pulses, were observed in certain stages of the cycle. Small mass pulses were present at all stages of the cycle; while their frequency remained unchanged, changes in other parameters were observed at different stages which did not always correlate with changes in mean PRL levels. Big mass pulses, on the other hand, presented a clear change in pulse frequency with values rising progressively from diestrus PM through proestrus to peak at estrus. Between estrus PM and metestrus AM these big mass PRL pulses essentially disappeared. In contrast to the marked changes in frequency, big mass PRL pulses were remarkably homogeneous in other quantitative characteristics. The results indicate that distinct changes in PRL pulsatility patterns occur during the estrous cycle; these changes are related to both the pattern and the quality of PRL pulses. Based on the observations of a companion study (28) and other data, we suggest that the genesis of the big mass and small mass PRL pulses involves dopaminergic and nondopaminergic mechanisms, respectively. The timing and selectivity of the changes in PRL pulsatile patterns suggest that those patterns may encode different signals for expression of the diverse actions of PRL on reproductive tissues.

Ectopic Cushing's syndrome with periodic hormonogenesis--a case suggesting a pathogenetic mechanism

We report on a case of ectopic Cushing's syndrome due to a thymic carcinoid tumour with periodic hormonogenesis. Periods of hormonal production averaged 27 days. Prior to bilateral adrenalectomy, mean (s.d) values of ACTH and cortisol were 202.1 (50.3) pg/ml and 46 (14.7) micrograms/dl, ACTH rising to 3996 +/- 425 pg/ml (P less than 0.01) and cortisol falling to 6.3 +/- 1.5 micrograms/dl (P less than 0.01) in the immediate postoperative period. During the late postoperative period (2-13 months following surgery) ACTH levels fell to 509.3 (123.8) pg/ml (P less than 0.01), but remaining even higher (P less than 0.01) than before adrenalectomy. The pattern of ACTH in the present case suggests the existence of a negative feedback exerted by the cortisol over tumoral ACTH.

Carriage of Neisseria meningitidis and Neisseria lactamica in a school population during an epidemic period in Spain

A study was made of the incidence of Neisseria meningitidis and N. lactamica in a school population; 2470 children aged between 5 and 7 years were studied from four schools in Alcala de Henares (Madrid). Nasopharyngeal swabs were taken in June, November and March, between 1979 and 1983. In all the surveys except one, the proportion of carriers of N. lactamica was higher than that of N. meningitidis, reaching a ratio of about 2:1 in the complete study. The predominant serogroup of meningococcus found was B (41%), with nongroupable strains reaching 43%. A study of serotypes within group B showed a predominance of nontypable strains (48.5%), while those strains considered to be most virulent (types 2 and 1, 8, 15) reached 40%. Eighteen per cent of N. lactamica strains were observed to agglutinate with antimeningococcal sera whilst the remainder of the strains were rough. When these strains were studied with the antiserum-agar technique, using antimeningococcal sera, a high percentage of strains cross-reacted with the meningococci. The susceptibility of strains to sulphadiazine, penicillin, ampicillin, chloramphenicol, rifampicin and spiramycin was determined. Finally an analysis was made of the effect that an elevated colonization rate of N. lactamica might have on colonization by meningococci. The necessity of using fine epidemiological markers in tracing virulent strains in a population at risk is stressed. Selective prophylactic measures are also necessary.