Alternative solution to global warming arising from CO2 emissions - partial neutralization of tropospheric H2CO3 with NH3

The impact of anthropogenic CO2 emissions to global warming arising from the "greenhouse effect" is presented, and atmospheric fate of NH3 summarized. It is proposed that if the near-future attempts of the United Nations to restrict the emissions of CO2 from fossil fuels end up with failure, it would be a rational alternative to increase the contribution of anthropogenic NH3, the only alkaline gaseous molecule in the troposphere, so as to partly neutralize atmospheric carbonic acid in aerosols in the form of ammonium bicarbonate, which would be eventually swept away by precipitation to the oceans where the HCO3- species is stable. Thus, addition of ammonium N-compounds to infertile nonurban land, especially in the form of urea, is recommended to enable volatilization losses of NH3 to the atmosphere. (c) 2007 American Institute of Chemical Engineers Environ Prog

Life detection experiments of the Viking Mission on Mars can be best interpreted with a Fenton oxidation reaction composed of H2O2 and Fe2+ and iron-catalysed decomposition of H2O2

The findings of the life detection experiments carried out during the Viking mission to Mars were reinterpreted with a chemical hypothesis. The labelled release (LR), pyrolytic release (PR) and gas exchange (GEx) experiments were interpreted with Fenton chemistry. Oxygen and carbon dioxide evolution from Martian soil upon wetting and nutrient addition Could be attributed to competition reactions between the Fenton-type oxidation of organic nutrients with the aqueous (hydrogen Peroxide + Fe(II)) combination and the iron-catalysed decomposition of hydrogen peroxide. A Substantial evolution of radioactive gas upon addition of labelled organic nutrient Solution to Soil, whereas the ceasing of this gas with a heat treated sample in the LR experiments, was attributed to Fenton oxidation and hydrogen peroxide thermal decomposition, respectively. The Peculiar kinetics of LR and PR experiments - that cannot be fully explained by other chemical or biochemical scenarios - were easily explained with this new hypothesis, i.e. limitation of the Fenton reaction may arise from the depletion of reactants, the build-up of ferric hydroxide oil soil and excessive scavenging by the organic nutrients of the generated hydroxyl radicals. Reabsorption or adsorption of evolved or introduced CO, may involve the formation of carbonate Compounds (e.g., magnesium carbonate and bicarbonate) on the Surface of alkalinized soil as a result Of the Fenton reaction

Ferric-o-phenanthroline adsorbed on a Nafion membrane: A novel optical sensor for antioxidant capacity measurement of food extracts

With increasing interest in consumption of antioxidant-rich food for fighting oxidative stress-related diseases, practical and low-cost tests for total antioxidant capacity (TAC) assessment are on the rise. We developed a sensitive solid membrane optical sensor for screening the TAC of food extracts and plant materials. The sensor was based on immobilizing a chromogenic oxidant, Fe(III)-o-phenanthroline (Fe(III)-phen), onto a Nafion cation-exchange membrane, and colorimetric measurement of the change in 510 nm-absorbance associated with highly-colored Fe(II)-phen formation upon reaction with antioxidants. The calibration curves with respect to the Fe(III)-phen sensing method of individual antioxidants comprising vitamins C and E, polyphenols and flavonoids were constructed, and their apparent molar absorptivities and linear concentration ranges determined. The limit of detection (LOD) and quantification (LOQ) for Trolox using the sensor were 0.26 and 0.87 mu M, respectively. The trolox equivalent antioxidant capacities (TEAC) of antioxidants found with the sensor were close to those of solution-phase Fe(III)-phen method, indicating that the immobilized reagent retained its reactivity toward antioxidants. This colorimetric sensor was validated through linearity, additivity, precision and recovery, showing its reliability and robustness. The sensor was tolerant to pH variations and turbidity, and used for screening the TAC values of some commercial fruit juices without pre-treatment. The sensor was more sensitive than the solution-phase method because the membrane concentrated the color from a larger volume solution. The sensor may be a good choice of field analytical chemists for rapid, simple and versatile determination of TAC of complex samples on-site (like a pH indicator-strip measuring H+ activity). (C) 2017 Elsevier B.V. All rights reserved

KINETIC INVESTIGATION AND SURFACE COMPLEXATION MODELING OF Cd(II) ADSORPTION ONTO FELDSPAR

The aim of this study is to determine the feldspar adsorption kinetics and isotherm of Cd(II) and to model the adsorption data with the aid of a metal-surface binary complexation approach. The adsorption of Cd(II) ion onto feldspar was approximated using a triple-site model by the aid of the FITEQL 3.2 computer program calculating the relative distribution of surface species. Experiments were carried out at I=0.1 ionic strength using an inert electrolyte (NaClO4). Of the three metal-binding surface sites of feldspar, it was assumed that (K,Na,Ca,Mg)X represents ion exchangable negative-charged sites, -S1OH silanol groups, and -S2OH pH-dependent aluminol groups. Metal hydrolysis was neglected under the experimental conditions employed, and Cd(II) was assumed to bind to the clay surface as the sole Cd2+ cation. The equilibrium constants of the reactions between Cd(II) ion and the surface sites were calculated using FITEQL 3.2. Cd(II) adsorption on feldspar showed Langmuiran character and pseudo-first order kinetics. The maximum adsorption capacity of feldspar for Cd(II) ions was found as 1.29 mg metal ion/g adsorbent. The results of this study are believed to facilitate the solution of environmental problems like metal ion migration and adsorptive treatment by clay minerals

Chromium speciation analysis by separation of Cr(III) from Cr(VI) on a XAD sorbent derivatized with shellac: a natural polymer

A XAD-shellac sorbent, synthesized by the impregnation of the natural polymer shellac ( purified product of the hardened resinous secretion of the lac insect Kerria lacca) on Amberlite XAD-16 copolymer backbone, has been developed for the separation of Cr(III) from Cr( VI), and preconcentration of Cr( III) from synthetic solutions and real samples. The preconcentration factor for Cr( III) was 75. All chromium determinations were made using the diphenyl carbazide spectrophotometric method after oxidizing Cr to chromate( VI) where necessary, and simultaneously with flame-AAS for confirmation. The dynamic breakthrough and batch capacities of this sorbent for Cr( III) were 0.3 and 0.9 mg g(-1), respectively, indicating that the ion-exchange mechanism was prevalent in the dynamic mode, whereas in the batch mode, the surface sites were also capable of exerting their chelating effects. When XAD-shellac was thoroughly washed with ammonium acetate solution prior to use in chromium speciation, the cationic (RH+) surface sites were probably neutralized to yield free acetic acid, and the resulting resin did not retain CrO42-. Thus, complete separation and speciation of Cr( III) from CrO42- was possible using this sorbent. The shellac-coated sorbent decomposed in alkaline solution (i.e. over pH 7.5), and therefore the retained Cr( III) was eluted with dilute (0.025 - 0.050 M) HCl. Thus, Cr( III) in admixture with Cr( VI) could be separated and recovered, without interference from the hexavalent state. XAD-shellac was not successful for Cr preconcentration from seawater, but was efficiently used for synthetic and real electroplating wastewater and CRMs such as SO-2 soil, San Joaquin soil, BCR 145R sewage sludge, with a recovery ratio for Cr( III)/Cr(VI) extending up to <= 98%

Modeling of cadmium(III) adsorption on kaolinite-based clays in the absence and presence of humic acid

Cadmium adsorption on kaolinite-based clays in the absence and presence of humic acid was modeled with the aid of the FITEQL 3.2 computer program using a modified Langmuir approach for capacity calculations. Formation of surface-metal ion and surface-humate-metal ion complexes was assumed using the DLM approach. As Cd(H) adsorption was ionic strength-dependent, the adsorption experiments were carried out in solutions containing two different concentrations of an inert electrolyte (0.1 M and 0.005 M NaClO4). The surface sites responsible for the adsorption were assumed to be the permanent charges, =S1OH silanol groups and carboxyl groups having pK(a) values close to that of the silanol groups, and =S2OH aluminol groups and phenol groups with pKa values close to that of the aluminol groups, because the studied clays (partly composed of clay soil) contained organic carbon. Cd2+ ions were assumed to bind to the surface in the form of outer-sphere X-2(2-) Cd2+ and inner-sphere =SOCd+ monodentate complexes. When humic acid was added, Cd(II) adsorption was modeled using a multi-site binding model by the aid of FITEQL3.2. The fit between model and experimental values was excellent in each case. Since the stability of the ternary surface complexes in the presence of humic acid was higher than that of the corresponding binary surface-cadmium ion complexes, the adsorption vs. pH curves were much steeper (and distinctly S-shaped) compared to the tailed curves observed in binary clay-cadmium ion systems. The clay mineral in the presence of humic acid probably behaved more like a chelating ion-exchanger for heavy metal ions than as a simple inorganic ion exchanger. (C) 2006 Elsevier B.V. All rights reserved

A manganese oxide (MnOx)-Based colorimetric nanosensor for indirect measurement of lipophilic and hydrophilic antioxidant capacity

Nanomaterials and composites containing metal oxides are increasingly being used in human health, cosmetics and food packaging applications, which may give rise to the evolution of reactive species on nanosurfaces by autoxidation with air O-2. In recent years, novel analytical approaches have been developed for total antioxidant capacity (TAC) determination, with special emphasis on nanoparticle-based sensors due to their low cost, easy use, rapid response and high precision. A nano-manganese oxide (nano-MnOx)-based spectrophotometric method was developed for the indirect capacity measurement of antioxidant compounds, based on the measurement of the decrease in the color intensity (at lambda(max) = 650 nm) of 3,3 ',5,5 '-tetramethylbenzidine cations (TMB+) in the presence of hydrophilic and lipophilic antioxidants. TMB+ cations were obtained via a redox reaction between MnOx NPs and the TMB chromophore in open air, and antioxidants caused a decrease of TMB+ color intensity. MnOx NPs could be easily and rapidly prepared at low cost. The linearity, repeatability and recovery parameters defining reliability and precision were tested to validate the sensing method. Depending on the type of tested antioxidant, the limit of detection (LOD) values were in the range of 1.23 x 10(-9) to 1.71 x 10(-7) mol L-1. The developed nanoprobe was applied to ternary synthetic mixtures of antioxidants to yield expected and found TAC values (as trolox-equivalents) in agreement. The potential interferents such as benzoic acid, citric acid, glucose and mannitol did not adversely affect the TAC determination. To test real samples, the method of standard addition of pure antioxidant compounds was applied to real samples such as green tea and orange juice