Nigel Sanders - Academia.edu (original) (raw)

Papers by Nigel Sanders

Industrial & Engineering Chemistry Fundamentals, Feb 1, 1986

Page 1. Ind. Eng. Chem. Fundam. 1986, 25, 169-171 169 Table 11. Evaluation of 1-pm Limestone (94.... more Page 1. Ind. Eng. Chem. Fundam. 1986, 25, 169-171 169 Table 11. Evaluation of 1-pm Limestone (94.6% CaC03) Particle Recovery in the Differential Reactor Ca found by limestone analysis after Ca sample, mg reaction, mg ...

Langmuir, Aug 1, 1991

Page 1. 1742 Langmuir 1991, 7, 1742-1748 Adsorption of Calcium Ions from Calcium Chloride Solutio... more Page 1. 1742 Langmuir 1991, 7, 1742-1748 Adsorption of Calcium Ions from Calcium Chloride Solutions onto Calcium Carbonate Particles? Yan C. Huang,$ Frederick M. Fowkes,ll Thomas B. Lloyd,$ and Nigel D. Sanders**% ...

Nordic Pulp & Paper Research Journal, 1993

The heats and electrokinetics of interaction of a precipitated calcium carbonate (PCC) filler wit... more The heats and electrokinetics of interaction of a precipitated calcium carbonate (PCC) filler with an anionic high molecular weight polyacrylamide (APAM) have been measured by solution microcalorimetry and by Doppler electrophoretic light scattering and electro-acoustic analyses. Detailed mechanistic studies of fillerlflocculant interaction are critical to achieving high retention aid system efficiency in filled papermaking furnishes. Variables in this work were PCC suspension solids (1-10%), APAM level (0.1-1.0%), conductivity (300-3000 pSlcm) and calcium ion concentration (10-100 mglkg as Ca). The heat development occurred in two steps with a slow secondary heat "tail" following the fast initial ("peak") response. It was found that the initial PCCIAPAM interaction was always exothermic with a "peak" heat expressed as an average per mole of APAM monomer ranging from 2.1 kJlmole at high polymer level to 40 kJlmole at low polymer level and low solids. The variation in initial heats of interaction with solids and polymer level suggest competition between flocculative (bridging) exothermic interactions and dispersive (loopinq) endothermic interactions at short times. The secondary "tails" are also observed in the electrokinetic data and likely indicate slow APAM reconformation into the more dispersive state. The study clearly shows the importance of polymer level and contact time control at low solids paper furnish conditions where the desired bridging interactions are generally at a disadvantage.

Journal of Molecular Spectroscopy, Mar 1, 1981

The microwave spectrum of methylmalonaldehyde has been measured and the molecule shown to be in a... more The microwave spectrum of methylmalonaldehyde has been measured and the molecule shown to be in an intramolecularly hydrogen-bonded (chelate ring) form in the gas phase. The spectrum shows the effects of two large amplitude internal motions: the torsion of the methyl group about its symmetry axis and the tunneling of the hydrogen-bond hydrogen through a potential barrier to an equivalent position (combined with an appropriate CH, rotation). The two motions are coupled through the torsion-inversion potential energy term of threefold symmetry in the torsional coordinate. A two vibration-plus-rotation model is developed and applied to explain the sizeable perturbations of the pure rotational transitions from a rigid rotor pattern in four ground-state sublevels. The observed torsioninversion splittings in the nondegenerate level (2.8004 cm-' for O=CH-C(CH,

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Author Institution: Department of ChemistryVibration-rotation perturbations in the microwave spec... more Author Institution: Department of ChemistryVibration-rotation perturbations in the microwave spectrum of the intramolecularly hydrogen-bonded molecule methylmalonaldehyde arise via tunneling through a barrier to C2vC_{2v}C2v symmetry. The splitting of the two lowest-lying states, 84 030 MHz for the normal isotopic species (I) and 10 776 upon deuteration of the hydrogen bond (II), has been determined by a treatment previously used on malonaldehyde. The threefold torsional barrier appears to be lowered as a consequence of the near symmetry (250 cal. For (I), 500 cal. for (II)) and varies between the tunneling levels, thus indirectly modifying the Coriolis problem. A complete analysis of the two internal motions with overall rotation is in progress."

Tappi Journal, 1993

Industrial & Engineering Chemistry Fundamentals, 1986

Nordic Pulp and Paper Research Journal, 1993

Journal of Molecular Spectroscopy, 1981

Journal of Colloid and Interface Science, 1988

Abstract The heats of immersion of a well-characterized mesoporous silica gel (Davisil 62) in sol... more Abstract The heats of immersion of a well-characterized mesoporous silica gel (Davisil 62) in solutions of six organic compounds (2-methylnaphthalene, benzothiophene, 2-methylbenzothiophene, pyridine, isoquinoline, and quinaldine) in isooctane (2,2,4-trimethylpentane) have been measured as a function of surface coverage by batch solution microcalorimetry. Adsorption isotherms at the silica/isooctane interface were obtained by conventional surface excess methods. The heat of adsorption of gaseous pyridine on silica was derived by correcting the heat of adsorption from the liquid for the bulk heats of mixing and phase change and the measured heats of wetting of silica covered with varioius preadsorbed amounts of pyridine in pyridine/isooctane solution. Connection was then made to the gas-phase adsorption data available for pyridine by the use of a rigorous thermodynamioc cycle. All of the compounds studied appeared to have site-limited adsorption (∼ 1 adsorbate per 2 surface silanol groups). 2-Methylnaphthalene and its sulfur aromatic analogs had very similar isotherms and low heats of adsorption from isooctane, in agreement with chromatographic experience. The one- and two-ring N-bases had high adsorption heats from isooctane which varied strongly with coverage (pyridine) or with adsorbate size (pyridine vs two-ring). It is argued, based upon the heats and entropies of adsorption, that the optimum hydrogen bond is the plane of the silica surface and that the observed large adsorbate steric effect reflected the geometry sensitivity of the hydrogen bond.

Langmuir, 1991