Hannu Rönkkömäki

Guidelines for NMR measurements for determination of high and low pKa values (IUPAC Technical Report)

Factors affecting the NMR titration procedures for the determination of pKa values in strongly basic and strongly acidic aqueous solutions (2 > pH > 0 and 14 > pH > 12) are analyzed. Guidelines for experimental procedure and publication protocols are formulated. These include: calculation of the equilibrium H+ concentration in a sample; avoidance of measurement with glass electrode in highly acidic (basic) solutions; exclusion of D2O as a solvent; use of an individual sample isolated from air for each pH value; use of external reference and lock compounds; use of a medium of constant ionic strength with clear indication of the supporting electrolyte and of the way the contribution of any ligand to the ionic strength of the medium is accounted for; use of the NMR technique in a way that eliminates sample heating to facilitate better sample temperature control (e.g., 1H-coupled NMR for nuclei other than protons, GD-mode, CPD-mode, etc.); use of Me4NCl/Me4NOH or KCl/KOH as a supporting electrolyte in basic solution rather than sodium salts in order to eliminate errors arising from NaOH association; verification of the independence of the NMR chemical shift from background electrolyte composition and concentration; use of extrapolation procedures.

Chemical and physical properties of cyclone fly ash from the grate-fired boiler incinerating forest residues at a small municipal district heating plant (6 MW)

In Finland, the new limit values for maximal allowable heavy metal concentrations for materials used as an earth construction agent came into force in July 2006. These limit values are applied if ash is utilized, e.g. in roads, cycling paths, pavements, car parks, sport fields, etc. In this study we have determined the most important chemical and physical properties of the cyclone fly ash originating from the grate-fired boiler incinerating forest residues (i.e. wood chips, sawdust and bark) at a small municipal district heating plant (6 MW), Northern Finland. This study clearly shows that elements are enriched in cyclone fly ash, since the total element concentrations in the cyclone fly ash were within 0.2-10 times higher than those in the bottom ash. The total concentrations of Cd (25 mg kg(-1); d.w.), Zn (3630 mg kg(-1); d.w.), Ba (4260 mg kg(-1); d.w.) and Hg (1.7 mg kg(-1); d.w.) exceeded the limit values, and therefore the cyclone fly ash cannot be used as an earth construction agent. According to the leached amounts of Cr (38 mg kg(-1); d.w.), Zn (51 mg kg(-1); d.w.) and sulphate (50,000 mg kg(-1); d.w.), the cyclone fly ash is classified as a hazardous waste, and it has to be deposited in a hazardous waste landfill.

Sorption of Pb(II), Cr(III), Cu(II), As(III) to peat, and utilization of the sorption properties in industrial waste landfill hydraulic barrier layers.

The low conductivity landfill barrier layers protect the groundwater and soil by limiting the water flow through the bottom layers of the landfill material. Many materials used in hydraulic barrier layers also have sorption properties which could be used to reduce environmental risks. The adsorption of lead, chromium, copper, and arsenic to peat was studied with a batch-type test and a column test for compacted peat, both without pH adjustment in acidic conditions. Peat adsorbed all the metals well, 40000mg/kg of lead, 13000mg/kg of chromium, and 8400mg/kg of copper in the column test. Arsenic was only tested in a batch-type test, and in that peat adsorbed 60mg/kg of arsenic. The column test showed heavy metals to be adsorbed on the surface layers of the compacted peat sample, on the first centimeter of the sample. The adsorption was much greater in the column test than in the batch-type test, partly due to the different pH conditions and the buffer capacity of the peat in the column test. The liquid/solid ratio of the column experiment represented a time period of approximately 40 years in a landfill, under Finnish climate conditions. The hydraulic conductivity of the peat decreased as it was compressed, but it already met the hydraulic conductivity limits set by European Union legislation for the hydraulic barrier layer (1x10(-9)m/s at a pressure of 150kPa for a 5-m layer), with a pressure of 50kPa. The results show that peat would be an excellent material to construct compacted, low hydraulic conductivity layers with adsorption properties in, e.g. industrial waste landfills.

Particle size distribution and dissolution properties of metals in cyclone fly ash

The particles in the examined cyclone fly ash were all smaller than 0.25 mm. in diameter, and particles smaller than 0.075 mm. in diameter accounted for 88.4 % of the ash weight. This result indicates that cyclone fly ash consists of particles with a small diameter. The metals in the cyclone fly ash were enriched in small particles. The highest concentrations for zinc, copper, lead, cadmium and molybdenum in the cyclone fly ash were found in the smallest particle size fraction (< 0.075 mm.) and for Barium, chromium, nickel, Vanadium and Cobalt in the second to smallest particle size fraction (0.075-0.125 mm.). From an environmental and toxicological standpoint, the smallest particles are of the greatest concern when ash is handed at landfill disposal sites (transport and disposal especially in stormy weather conditions), and some studies have reported risks to workers from prolonged exposure to ash. The results of the comparison of various dissolution methods for metals showed that the digestion procedures with nitric acid alone (USEPA 3051) or with a mixture of nitric acid + hydrogen peroxide (USEPA 3050B) slightly underestimated the metal concentrations in the cyclone fly ash. Although the use of hydrofluoric acid is often necessary for the determination of a number of elements associated with siliceous minerals, its use can result in loss of trace elements during dissolution.

Stability constants of cesium complexes with 18-crown-6 in ionic liquids

The stability constants of the complex[Cs(18C6)]+ (18C6 is 18-crown-6 (L)) in N-butylpyridinium methyl sulfate (I) and of the complex [Cs(18C6)2]+ in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (II) were measured by using 133Cs NMR spectroscopy at 23°C. It was found that logK(Cs + L) in solvent I is 1.20±0.13 and logK(CsL + L) in solvent IIis 1.18±0.05. For the complex [Cs(18C6)2]+, the dependence of its stability constant on the temperature in the 23–50°C range was obtained and the enthalpy change in the complexation was determined: ΔH(CsL + L)= −47 kJ/mol. It was demonstrated that the enthalpy change is favorable for the formation of [Cs(18C6)2]+, while the entropy change hinders the complexation.

Stability constant of the sodium complex with 18-crown-6 in the mixed water-ionic liquid solvent

The stability constant of the Na+ complex with dibenzo-18-crown-6, [Na(DB18C6)]+, was measured by the 23Na NMR method in the mixed water-ionic liquid solvent at 23°C. N-Butyl-4-methylpyridinium tetrafluoroborate (BMPTB) was used as room temperature ionic liquid. It was found that for the solvent containing 0.8 mol fraction of water and 0.2 mol fraction of BMPTB, the value log K = 0.77 ± 0.05. The addition of BMPTB to water was found to increase the solubility of the crown ether but to decrease the sodium nitrate solubility.

Release of metals from grate-fired boiler cyclone ash at different pH values

Abstract The concentrations of metals (Ba, Cr, Zn, Cd, Ni, Cu, As, Hg, Pb, Mo, Se and Sb) extractable from cyclone ash, obtained from a municipal district heating plant (6MW) incinerating forestry and sawmill residues, was studied as a function of pH (1.1-12.8) at a liquid-to-solid (L/S) ratio of 10L/kg. The following main fractions were obtained: (1) metals (Ba, Cr, Zn, Cd, Ni, Cu, As, Hg, Pb and Sb) that were primarily extractable in extreme or strongly acidic conditions; (2) metals (Cr and Zn) that expressed amphoteric behaviour, i.e. they were extractable both in acidic (low pH) and alkaline (high pH) conditions, but were relatively insoluble at neutral pH values; and (3) metals (Mo and Se) which were primarily extractable only in alkaline conditions. The maximum extraction recovery (R) value (%) of the metals, which varied between 1.3 and 93.4%, indicates that most of the metals in cyclone ash are not easily soluble in the conditions normally found in nature.

Complexation of strontium with triisopropyl ester of dichloromethylene-bis(phosphonic acid) in water and ionic liquids

AbstractThe complexation of strontium with triisopropyl ester of dichloromethylene-bis(phosphonic acid) (NaL) is examined using 31P NMR in water and the hydrophilic ionic liquid 1-butyl-3-methylimidazolium dicyanamide ([BMIM][N(CN)2]): The values of stability constants of complex SrL are reported: logK1 = −0.37 ± 0.05 (water, I = 0.07 mol/L, 25°C) and 3.0 ± 0.1 (ionic liquid, 25°C).

Adsorption of Ni(II) and Cd(II) in Compacted Peat and the Utilization of the Adsorption Properties in Hydraulic-Barrier Layers in Tailing Impoundments

AbstractLandfills and tailing impoundments contain barrier layers that prevent the migration of contaminants into groundwater by slowing down the water flow through the structures. Many materials used in hydraulic barrier layers also have sorption properties, which could be utilized to reduce environmental risks. The adsorption of Ni(II) and Cd(II) on peat was studied using a single metal column test. Two samples with different dry unit weights, low-density (LD) and high-density (HD) peat, were tested. A batch test was made for comparison. Both samples in the column test adsorbed the metals well; peat adsorbed 9,500  mg/kg of nickel and 11,200  mg/kg of cadmium. The adsorption was twice as high in the column test as in the batch test. Cadmium adsorbed strongly on the top layers of the sample, whereas the adsorption profile of nickel was more even through the sample. The density of the peat did not affect the maximum adsorption capacity. In HD peat, the heavy metals adsorbed more on the top layers of the s...