A novel pre-oxidation method for elemental mercury removal utilizing a complex vaporized absorbent.

A novel semi-dry integrative method for elemental mercury (Hg(0)) removal has been proposed in this paper, in which Hg(0) was initially pre-oxidized by a vaporized liquid-phase complex absorbent (LCA) composed of a Fenton reagent, peracetic acid (CH3COOOH) and sodium chloride (NaCl), after which Hg(2+) was absorbed by the resultant Ca(OH)2. The experimental results indicated that CH3COOOH and NaCl were the best additives for Hg(0) oxidation. Among the influencing factors, the pH of the LCA and the adding rate of the LCA significantly affected the Hg(0) removal. The coexisting gases, SO2 and NO, were characterized as either increasing or inhibiting in the removal process, depending on their concentrations. Under optimal reaction conditions, the efficiency for the single removal of Hg(0) was 91%. Under identical conditions, the efficiencies of the simultaneous removal of SO2, NO and Hg(0) were 100%, 79.5% and 80.4%, respectively. Finally, the reaction mechanism for the simultaneous removal of SO2, NO and Hg(0) was proposed based on the characteristics of the removal products as determined by X-ray diffraction (XRD), atomic fluorescence spectrometry (AFS), the analysis of the electrode potentials, and through data from related research references.

Nitric acid recycling and copper nitrate recovery from effluent.

The recycling of nitric acid and copper nitrate contained in an industrial effluent was studied. The experiments conducted on such a medium showed that the presence of copper nitrate significantly improves nitric acid-water separation during distillation in an azeotropic medium. At the temperature of the azeotrope, however, this metal salt starts to precipitate, making the medium pasty, thus inhibiting the nitric acid extraction process. The optimisation of parameters such as column efficiency and adding water to the boiler at the azeotrope temperature are recommended in this protocol in order to collect the various components while avoiding the formation of by-products: NOx compounds. Thus, the absence of column, along with the addition of a small volume of water at a temperature of 118 °C, significantly increases the yield, allowing 94 % nitric acid to be recovered at the end of the process, along with the residual copper nitrate. The resulting distillate, however, is sufficiently dilute to not be used as is. Rectification is required to obtain concentrated nitric acid at 15 mol·l(-1), along with a weakly acidic distillate from the distillation front. This latter is quenched using potassium hydroxide and is used as a fertiliser solution for horticulture or sheltered market gardening. This process thus allows complete recycling of all the medium's components, including that of the distillate resulting from the nitric acid rectification operation.

Interactions of gaseous HNO3 and water with individual and mixed alkyl self-assembled monolayers at room temperature.

The major removal processes for gaseous nitric acid (HNO3) in the atmosphere are dry and wet deposition onto various surfaces. The surface in the boundary layer is often covered with organic films, but the interaction of gaseous HNO3 with them is not well understood. To better understand the factors controlling the uptake of gaseous nitric acid and its dissociation in organic films, studies were carried out using single component and mixtures of C8 and C18 alkyl self-assembled monolayers (SAMs) attached to a germanium (Ge) attenuated total reflectance (ATR) crystal upon which a thin layer of SiOx had been deposited. For comparison, diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) studies were also carried out using a C18 SAM attached to the native oxide layer on the surface of silicon powder. These studies show that the alkyl chain length and order/disorder of the SAMs does not significantly affect the uptake or dissociation/recombination of molecular HNO3. Thus, independent of the nature of the SAM, molecular HNO3 is observed up to 70-90% relative humidity. After dissociation, molecular HNO3 is regenerated on all SAM surfaces when water is removed. Results of molecular dynamics simulations are consistent with experiments and show that defects and pores on the surfaces control the uptake, dissociation and recombination of molecular HNO3. Organic films on surfaces in the boundary layer will certainly be more irregular and less ordered than SAMs studied here, therefore undissociated HNO3 may be present on surfaces in the boundary layer to a greater extent than previously thought. The combination of this observation with the results of recent studies showing enhanced photolysis of nitric acid on surfaces suggests that renoxification of deposited nitric acid may need to be taken into account in atmospheric models.

Modifications in the nitric acid oxidation of D-glucose.

The nitric acid oxidation of D-glucose was reinvestigated in an effort to better understand and improve the oxidation and subsequent work up steps. The oxidation was carried out using a computer controlled reactor employing a closed reaction flask under an atmosphere of oxygen which allowed for a catalytic oxidation process with oxygen as the terminal oxidant. Removal of nitric acid from product included the use of both diffusion dialysis and nanofiltration methodologies. Product analysis protocols were developed using ion chromatography.

Recovery of nitric acid from waste etching solution using solvent extraction.

A process was developed to recover nitric acid from the waste stream of wafer industry using solvent extraction technique. Tributyl phosphate (TBP) was selected among several extractants because of its better selectivity towards HNO(3), overall superiority in operation, favorable physical properties and economics. The waste solution containing 260 g/L CH(3)COOH, 460 g/L HNO(3), 113 g/L HF and 19.6g/L Si was used as feed solution for process optimization. In the pre-treatment stage >99% silicon and hydrofluoric acid was precipitated out as Na(2)SiF(6). Equilibrium conditions for HNO(3) recovery were optimized from the batch test results as: four stages of extraction at an organic:aqueous (O:A) ratio of 3, four stages of scrubbing at O:A ratio of 5 and five stages of stripping at an O:A ratio of 1.5. The extraction of HNO(3) was suppressed by the presence of acetic acid (HAc) in the feed solution. To examine the feasibility of the extraction system a continuous operation was carried out for 200 h using a multistage mixer-settler. The concentration of pure HNO(3) recovered was 235 g/L with a purity of 99.8%.

[Effects of selective extraction on microorganisms on biomembrane in natural water body].

By the methods of direct viable count and plate count, this paper studied the effects of different selective extractants on the bacteria, algae and protozoan on the biomembrane in natural water body. The results indicated that the stronger the extraction ability of selective extractant, the fewer the living microorganisms on the biomembrane after extraction. Compared with the control, the percentages of living microorganisms on the biomembrane were 27.6, 14.1 and 0.01, respectively, after extracted by hydroxylamine hydrochloride (0.01 mol x L(-1) NH2OH.HCl + 0.01 mol x L(-1) HNO3), sodium dithionite (0.4 mol x L(-1) Na2S2O4, pH 6.0), and acidified ammonium oxalate. Very few bacteria was left after extracted by nitric acid (15% HNO3), and no microorgariisms could be detected after extracted by H2O2/HNO3, suggesting that the use of selective extractants affected the activity of biomembrane. With the decreasing amount of microorganisms on the biomembrane after treated with selective extractants, the adsorption of heavy metals by the biomembrane was gradually depressed.

The formation, role and removal of NO3-N during corona discharge in air for phenol removal.

Pulsed corona discharge carried out in the gas phase has been shown to be a low cost solution for wastewater treatment. In this study, the results show that the nitrogen dissociated during corona discharge in the gas phase formed nitric acid in solution, which resulted in a drop in solution pH. The phenol removal could be described in accordance with a first-order reaction in a basic buffer solution, but not in initial neutral and basic non-buffered solutions. This indicates that basic conditions facilitate phenol removal, whilst the formation of nitric acid in solution resulted in decrease in the phenol removal rate. This study also shows that most of the oxidants used for phenol removal came mainly from the dissociation of water molecules at the surface of the liquid phase and/or the gas phase very close to the liquid surface in discharging conditions, not from the gas dissociation in the bulk gas phase, and therefore, it is more effective to keep the solution basic than to change the component of gas in the reactor when removing phenol from water using corona discharge.

A hybrid liquid-phase precipitation (LPP) process in conjunction with membrane distillation (MD) for the treatment of the INEEL sodium-bearing liquid waste.

A novel hybrid system combining liquid-phase precipitation (LPP) and membrane distillation (MD) is integrated for the treatment of the INEEL sodium-bearing liquid waste. The integrated system provides a "full separation" approach that consists of three main processing stages. The first stage is focused on the separation and recovery of nitric acid from the bulk of the waste stream using vacuum membrane distillation (VMD). In the second stage, polyvalent cations (mainly TRU elements and their fission products except cesium along with aluminum and other toxic metals) are separated from the bulk of monovalent anions and cations (dominantly sodium nitrate) by a front-end LPP. In the third stage, MD is used first to concentrate sodium nitrate to near saturation followed by a rear-end LPP to precipitate and separate sodium nitrate along with the remaining minor species from the bulk of the aqueous phase. The LPP-MD hybrid system uses a small amount of an additive and energy to carry out the treatment, addresses multiple critical species, extracts an economic value from some of waste species, generates minimal waste with suitable disposal paths, and offers rapid deployment. As such, the LPP-MD could be a valuable tool for multiple needs across the DOE complex where no effective or economic alternatives are available.

[Recovery process of nitric acid, copper and nickel in deplating wastewater].

The recovery process of nitric acid, copper and nickel in deplating wastewater was developed by using the combined technique of distillation, solvent extraction and precipitation. The conditions of the separation of copper and nickel by solvent extraction using P507 in kerosene and stripping copper with H2SO4 were specially investigated and the optimal parameters were determined. The results of experiment indicated that the recovery ratio of nitric acid was 97.8%, and under the optimized conditions of extraction process, concentration of original effluence ranged in 15-20 mg/mL copper, 5-10 mg/mL nickel, pH 1-2, concentration of extractant was 35% (V/V), saponification degree was 60%, phase ratio was 1:1, reaction time was 2 min, temperature ranged in 20 degrees C-25 degrees C, the one stage extraction efficiency of copper was higher than 90%, the separation ratio of copper and nickel was up to 75; copper and nickel could be completely separated by a continuous countercurrent three-stage extraction. The nickel could be recovered from the water phase by precipitating with NaOH and the recovery ratio of nickel reached up to 99.9% by controlling pH in solution within 10-11. After these treatment, the effluent could meet the national standards of wastewater discharge.