ABSTRACT
Membrane filtration is an effective technique for separating micro- and nano-sized oil droplets from harmful oil-contaminated waters produced by numerous industrial activities. However, significant flux reduction discourages the extensive application of this technology; therefore, developing antifouling membranes is necessary. For this purpose, various titanium dioxide/carbon nanotube (TiO2/CNT) nanocomposites (containing 1, 2, and 5 wt.% multi-walled CNTs) were used for the modification of polyvinylidene fluoride (PVDF) ultrafilter (250 kDa) membrane surfaces. The effects of surface modifications were compared in relation to the flux, the filtration resistance, the flux recovery ratio, and the purification efficiency. TiO2/CNT2% composite modification reduced both irreversible and total filtration resistances the most during the filtration of 100 ppm oil emulsions. The fluxes were approximately 4-7 times higher compared to the unmodified PVDF membrane, depending on the used transmembrane pressure (510, 900, and 1340 L/m2h fluxes were measured at 0.1, 0.2, and 0.3 MPa pressures, respectively). Moreover, the flux recovery ratio (up to 68%) and the purification efficiency (95.1-99.8%) were also significantly higher because of the surface modification, and the beneficial effects were more dominant at higher transmembrane pressures. TiO2/CNT2% nanocomposites are promising to be applied to modify membranes used for oil-water separation and achieve outstanding flux, cleanability, and purification efficiency.
ABSTRACT
Surgical treatment of liver metastases, under certain conditions, can be a step of a multidisciplinary treatment strategy for advanced malignant disease. Nevertheless, it is not the same if metachronous or synchronous metastases are planned to be treated. Indications for surgery are the most clearly defined and accepted in cases of colorectal and neuroendocrine liver metastases. At the same time, the steps of the traditional oncotherapy has changed in the management of synchronous colorectal metastases: the novel concept of the treatment strategy is removing the liver metastases before the colorectal primary. The role of surgery is less clear and defined in the management of metastases from other, non-colorectal and non-neuroendocrine primaries. The main purpose is to evaluate which kind of criteria should be fulfilled to indicate the resection of liver metastases, which are the conditions that, when present, may provide a benefit to a patient from surgery, improving survival. These criteria have not been clarified precisely yet; randomized prospective trials are needed. Consensus recommendations in such cases could be determined based on the results of the mentioned trials.
