A comparison was undertaken of the sorption response of oxycellulose and initial linters, i.e. the short fibres that adhere to cotton seed after ginning, towards Fe 2+ , Ca 2+ and Cd 2+ ions in fibrous slurries. The exceptional adsorption capability of oxycellulose towards metal ions (particularly Cd 2+ ions) was confirmed. However, such adsorption processes are quite complicated and are influenced by the solubility of oxycellulose, its composition and the character of the components released into the supernatant, as well as by the presence of other competitive substances and ions in the aqueous solution. The adsorption capacity of oxycellulose increases with increasing-COOH group content and is distinctly increased by the presence of other competitive ions in the aqueous solution. Most probably, this enhanced adsorption capacity of the support bears some analogy to the superficial aggregation (flocculation) induced by the presence of foreign substances.
Oxidized cellulose (oxycellulose) was very effectively used in the form of filter sheets to remove some metal ions from water and from aqueous solutions. Furthermore, oxycellulose was applied in an ion-exchange column and in a batch process. The mechanisms of the sorption process inside oxycellulose as well as the kinetics of sorption were studied. A comparison of oxycellulose and other adsorption components such as zeolites and ion-exchange resins was made. The affinity of oxycellulose to metal ions was determined to be in the following order:The use of oxycellulose was very effective, especially in the form of sorption filters, because this allowed us to use a simple filtration process. Moreover, the specific loading amount of the filter cake was higher for filtration than for the column process under comparable conditions. Oxycellulose in a glass column behaved similarly to an ion-exchange resin.It showed approximately constant efficiency until the sorption capacity of the adsorbent was exhausted, and then it suddenly dropped.
The dyeing of modified pulp, particularly with regard to the mechanism involved, was studied. The reaction mechanism for the modification of cellulose fibres in aqueous solution by cationic agents was also described. The results obtained were expressed in the form of adsorption isotherms. The capture of molecules, colloidal particles, etc. during the adsorption processes involving modified pulp could be explained by two possible mechanisms: (i) aggregation (coagulation or flocculation) in solution followed by adsorption and (ii) surface aggregation (coagulation or flocculation). Surface aggregation appeared to be the most likely for pulp with a low degree of modification. The typical Langmuir adsorption isotherm correlated the data obtained for unmodified pulp very well.
Vapour diffusion in a porous web material followed by its absorption or condensation is a typical process for all porous materials particularly on polymeric and natural basis. The description of kinetic weight increment increase during this process was proposed by use of a relatively simple function with adequately defined theoretical background. It was shown that this kinetic process is controlled by vapour diffusion through porous web material. This tool in connection with observations at different air relative humidity and with use of relatively simple technique enables one to evaluate the structure properties and its structure homogeneity, that is, the uniformity character of the porous stratified web material. Utilization of this description was demonstrated during moistening kinetics of paper web of different composition from primary and secondary fibres on lignocellulosic and only cellulosic basis with different ash content.
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