Special crystalline and amorphous silicates, soda/silicate compounds as well as zeolite P are offered as an alternative to zeolite A. These builders have in common that they contribute to the softening of water and thus to the inhibition of coarse precipitations which may lead to incrustations on textiles. The mechanisms of these builders are however quite different. Whereas the builder efficacy of zeolites is essentially due to the ion exchange capacity, the builder properties of the special silicates are largely determined by the dissolution kinetics and the structure of the formed silicate anions. Physicochemical investigations and washing tests show that zeolite P as well as the special silicates may partially or completely substitute zeolite A. A benefit of zeolite P is, that the calcium binding is quicker and substantially stronger in comparison to zeolite A. As a consequence, the amount of organic cobuilders (e.g. polycarboxylates) that have to be used in combination with zeolite A can be reduced in the detergent formulas. Furthermore, zeolite P exhibits a superior uptake for non-ionic surfactants in comparison to zeolite A. This is essentially due to the smaller particle size of zeolite P and may be of potential advantage for special production technologies. Additionally, zeolite P shows a better compatibility with bleach components in some detergent formulas. All silicates are distinguished from the heterogeneous zeolites by several properties : they are principally soluble, they contribute to the alkalinity of the washing liquor and they are generally more compatible to sensitive bleach components like percarbonate. Soda/silicate compounds are especially suited for the partial substitution of zeolite A. On the other hand, crystalline layered silicates (like δ-sodium disilicate) and especially certain amorphous silicates with reduced solubility may completely substitute zeolite due to their superior antiincrustation efficiency. A prerequisite for the maintainance of the good builder efficiency of the silicates is a gentle processing with a far reaching preservation of the silicate or granule structure. The possibilities to process zeolites are surely more versatile. The future market development of the silicates as well as of zeolite P depends particularly on the price development.

Special crystalline and amorphous silicates soda/silicate compounds as well as zeolite P are offered as an alternative to zeolite A. These builders have in common that they contribute to the softening of water and thus to the inhibition of coarse precipitations which may lend to incrustations on textiles The mechanisms of these builders are however quite different. Whereas the builder efficacy of zeolites is essentially due to the ion exchange capacity, the builder properties of the special silicates are largely determined by the dissolution kinetics and the structure of the formed silicate anions. Physicochemical investigations and washing tests show that zeolite P as well as the special silicates may partially or completely substitute zeolite A. A benefit of zeolite P is, that the calcium binding is quicker and substantially stronger in comparison to zeolite A. As a consequence, the amount of organic cobuilders (e.g. polycarboxylates) that have to be used in combination with Zeolite A can be reduced in the detergent formulas. Furthermore, zeolite P exhibits a superior uptake for non-ionic surfactants in comparison to zeolite A. This is essentially due to the smaller particle size of zeolite P and may be of potential advantage for special production technologies. Additionally, zeolite P shows a better compatibility with bleach components in some detergent formulas. All silicates are distinguished from the heterogeneous zeolites by several properties: they are principally soluble, they contribute to the alkalinity of the washing liquor and they are generally more compatible to sensitive bleach components like percarbonate. Soda/silicate compounds are especially suited for the partial substitution of zeolite A. On the other hand crystalline layered silicates (like delta-sodium disilicate) and especially certain amorphous silicates with reduced solubility may completely substitute zeolite due to their superior antiincrustation efficiency. A prerequisite for the maintainance of the good builder efficiency of the silicates is a gentle processing with a far reaching preservation of the silicate or granule structure. The possibilities to process zeolites are surely more versatile. The future market development of the silicates as well as of zeolite P depends particularly on the price development.

High contents of fillers such as kaolin or calcium carbonate limit the use of waste paper, especially in tissue paper production. In order to determine the effect of flotation reagents on the removal of fillers, adsorption, zeta potential, and particle size measurement,s as well as flotation experiments using model dispersions of calcium carbonate, kaolin, and cellulose fibers were carried out. The adsorption of the cationic polymer starts at low initial concentrations on the negatively charged filler surfaces and cellulose fibers. However, due to the steeper slope of the adsorption isotherm on the fillers, the polymer is preferentially adsorbed on the fillers. Furthermore, the adsorption of the polymer causes an increase in the particle size of the fillers. Anionic surfactants are generally better suited for waste paper systems containing calcium carbonate than for those with kaolin. This is due to the fact that the adsorption onto calcium carbonate occurs at lower concentrations than that onto kaolin. Calcium ions dissolved in the pulp improve the adsorption of anionic surfactant onto kaolin and are necessary for a sufficiently high recovery of the fillers.

Investigations were carried out on model systems such as filler suspensions or artificial mixtures of wood pulp and fillers. Particle size distributions and flotation recovery rates were determined as a function of the concentration of the major dissolved substances in the pulp. These measurements were correlated with results obtained from filler containing waste paper. It was found that the flotation results are significantly dependent on the type of filler, its particle size and the presence of dispersants like sodium silicate in the pulp.

AbstractUse of Surfactants for Mechanical Liquid Separation. Mechanical dewatering of finegrained solid materials can be improved by the addition of surfactants. As interface‐active substances surfactants reduce surface tension and consequently the capillary forces within the bed of solid particles. A hydrophobization of the solid surface due to the adsorption of surfactants may contribute to further reduction of moisture as well. The development of non‐foaming surfactants enables the use without distrubing other ongoing processes by the formation of foam. Investigations on the interaction between the adsorption behaviour, type of material surface, and contact time during dewatering processes support the optimization of dewatering agents. The use of surfactants is an attractive means of improving or replacing other methods of mechanical dewatering.

The selective flotation of kaolinite for the separation from feldspar is difficult because the two minerals have very similar surface properties and the flotation feed contains a high proportion of extremely fine particles (< 5-mu-m); nevertheless, this process is of great practical importance. The alkyl amines usually used as collectors in kaolinite flotation processes only give satisfactory results in strongly acidic pulps.Reagent systems based on cationic surfactants were developed to enable kaolinite to be separated from feldspar by flotation in weakly acidic to neutral pulps. Special importance is attached to the addition of suitable multivalent cations in this context. Furthermore, in the presence of these multivalent cations flotation can be carried out with suitable anionic surfactants that previously could not be used because of their low effectiveness.With the help of basic studies of the charge on the minerals and the adsorption of the surfactants and the multivalent cations on the mineral surfaces, a good understanding of the action mechanism of the developed reagents was obtained. During flotation with cationic surfactants the recovery of feldspar is reduced, and the selectivity of the flotation is thus improved, as a result of aluminium ions being competitively adsorbed rather than collector ions. By contrast, in the case of flotation with anionic surfactants the activation of the kaolinite surface by the multivalent cations is the crucial precondition for selective flotation. The effectiveness of the new reagent systems was demonstrated in laboratory scale flotation tests on natural kaolinite ores.

This work is concerned with basic studies on the flotative separation of three minerals: apatite, hornblende, and magnetite. Two anionic surfactants that differed in the solubility of their calcium salts were chosen as collectors (oleate and alkylsulphosuccinate). The flotation behavior of the minerals was characterized by determing adsorption isotherms and zeta-potentials, and by carrying out microflotation tests. It was shown that both collectors are adsorbed on all mineral surfaces, but at different equilibrium concentrations. As the concentration range of the onset of adsorption on apatite is lower than that on hornblende and magnetite, apatite can be separated from a mineral mixture or a respective ore. Calcium ions are often present in the flotation pulp and influence the adsorption behavior of the collectors. Due to the slight solubility of the calcium-containing minerals, apatite and hornblende, precipitation of calcium oelate occurs, as well as adsorption of oleate when a certain concentration is reached. Higher calcium ion concentrations induce more precipitation and make oleate less effective as a collector. Because of the higher solubility of the calcium alkylsulphosuccinate, precipitation does not occur in the considered concentration range. In contrast to oleate, the adsorption of alkylsulphsuccinate is shifted to lower equilibrium concentrations by calcium ions adsorbed on the mineral surface. This makes alkylsulphosuccinate a more effective collector in water with high calcium ion concentrations. The sequence of adsorption and hence, of flotation is not influenced by calcium ions, i.e., apatite, but not hornblende, can be separated from magnetitde.

This work is concerned with basic studies on the flotative separation of three minerals: apatite, hornblende, and magnetite. Two anionic surfactants that differed in the solubility of their calcium salts were chosen as collectors (oleate and alkylsulphosuccinate). The flotation behavior of the minerals was characterized by determing adsorption isotherms and zeta-potentials, and by carrying out microflotation tests. It was shown that both collectors are adsorbed on all mineral surfaces, but at different equilibrium concentrations. As the concentration range of the onset of adsorption on apatite is lower than that on hornblende and magnetite, apatite can be separated from a mineral mixture or a respective ore. Calcium ions are often present in the flotation pulp and influence the adsorption behavior of the collectors. Due to the slight solubility of the calcium-containing minerals, apatite and hornblende, precipitation of calcium oelate occurs, as well as adsorption of oleate when a certain concentration is reached. Higher calcium ion concentrations induce more precipitation and make oleate less effective as a collector. Because of the higher solubility of the calcium alkylsulphosuccinate, precipitation does not occur in the considered concentration range. In contrast to oleate, the adsorption of alkylsulphsuccinate is shifted to lower equilibrium concentrations by calcium ions adsorbed on the mineral surface. This makes alkylsulphosuccinate a more effective collector in water with high calcium ion concentrations. The sequence of adsorption and hence, of flotation is not influenced by calcium ions, i.e., apatite, but not hornblende, can be separated from magnetitde.

Im Vergleich zur konventionellen Prozeßsteuerung stellt der Einsatz von Prozeßrechnern zur Überwachung und Führung technischer Prozesse neue Anforderungen an die Schnittstelle Mensch — Maschine. So sind bei der Gestaltung dieser Schnittstelle auf der einen Seite die Forderungen des technischen Systems, auf der anderen Seite aber besonders die Fähigkeiten und Grenzen des Menschen als Bediener zu berücksichtigen, um eine optimale Aufgabenteilung zwischen beiden zu erreichen.