Synthetic dyes or colorants are key chemicals for various industries producing textiles, food, cosmetics, pharmaceutics, printer inks, leather, and plastics. Nowadays, the textile industry is the major consumer of dyes. The mass of synthetic colorants used by this industry is estimated at the level of 1 ÷ 3 × 105 tons, in comparison with the total annual consumption of around 7 × 105 tons worldwide. Synthetic dyes are relatively easy to detect but difficult to eliminate from wastewater and surface water ecosystems because of their aromatic chemical structure. It should be highlighted that the relatively high stability of synthetic dyes leads to health and ecological concerns due to their toxic, mutagenic, and carcinogenic nature. Currently, removal of such chemicals from wastewater involves various techniques, including flocculation/coagulation, precipitation, photocatalytic degradation, biological oxidation, ion exchange, adsorption, and membrane filtration. In this review, a number of classical and modern technologies for synthetic dye removal from industry-originated wastewater were summarized and discussed. There is an increasing interest in the application of waste organic materials (e.g., compounds extracted from orange bagasse, fungus biosorbent, or green algal biomasses) as effective, low-cost, and ecologically friendly sorbents. Moreover, a number of dye removal processes are based on newly discovered carbon nanomaterials (carbon nanotubes and graphene as well as their derivatives).

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There is great interest in the search for multifunctional waste-based materials that may be applied as environmentally friendly adsorbents. Iron-rich sludge from ground drinking-water treatment plants may be considered a potential adsorbent for various water contaminants. This material is generated during ground water purification because of the excess of metal ions in water (Fe, Mn). In practice, this sludge is frequently disposed of as waste material and, so far, is not commonly applied as the adsorption base. Our research aims to explore the adsorption potential of iron sludge for selected synthetic dyes, including malachite green, ponceau 4R, and brilliant blue FCF. Experimental data were performed using iron sludge collected from the Groundwater Treatment Plant in Koszalin, Poland, and comparing it with adsorption properties of commercial activated carbons (Norit SA Super and Norit CA 1). The kinetics, adsorption isotherms, and temperature influence on the removal of target dyes were investigated and discussed. Preliminary experimental data have revealed that iron sludge can be considered an adsorbent for the removal of cationic dyes.

The main goal of this review is to summarize practical approaches concerning the application of microfluidic systems for the analysis of various biomarkers and pollutants, as well as microbes, in water and wastewater matrixes. This problem involves multidisciplinary expertise combining research knowledge from various areas, including wet chemistry, biochemistry, physical chemistry, molecular biology, genetics, signal processing, microelectronics material science, and separation science. It has been documented that fairly primitive but fast and inexpensive screening methods involving paper-based analytical devices (PADs) and micro total analytical systems (μTAS) can be considered as serious alternatives to their more advanced counterparts such as GC, HPLC, and capillary electrophoresis coupled to various sophisticated detectors (e.g., multiwavelength spectrophotometers such as UV-Vis/DAD and mass spectrometers). The main advantage of PAD- and μTAS-driven technology is that such sensing devices may work under on-site and real-time conditions and measure a number of physical parameters and chemical factors simultaneously. Moreover, hybrid miniaturized analytical systems may combine sensing and data acquisition modules with common mobile phones and electronic devices working with global positioning systems and communicating through the Internet.

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