|Opis:||Colored wastewater is a problem in all textile industries. With the desire to reuse dyes, minimize contamination and increase the efficiency of dyeing, technologies are being developed that would purify wastewater in the most efficient and cost-effective way before being discharged into a watercourse. Previous research has shown that membrane adsorption is one of the more effective physical methods of separating dyes.
In the research part, we investigated the possibilities and ways by which cationic dyes can be successfully separated using cellulose-based membrane adsorbents. For this purpose, two types of cellulose-based membranes were manufactured: the first was synthesized using cellulosic nanofibrils and carboxymethylated cellulose, and the second was prepared using commercial bacterial cellulose. An additional modification was included in the experimental design, ie oxidation of bacterial cellulose and variations between the ratios of cellulose nanofibrils and carboxymethylated cellulose in order to study the effect of the presence of different functional groups on the functionality of membranes. The cationic dyes used are C.I. Basic Blue anthracnone dye 47 and C.I. Basic Yellow azo dye 29.
The methods used to analyze the physicochemical and morphological properties of the membranes are attenuated full reflectance infrared spectroscopy with Fourier transform (ATR - FTIR), goniometry, potentiometric titration and confocal optical microscopy. UV - VIS spectroscopy was used to study the adsorption efficiency and the adsorption rate (kinetics) of two cationic dyes on individual membranes.
In the ATR - FTIR spectra of membranes, the presence of cellulose 3340 cm-1 could be identified, the formation of new bonds attaching to aldehyde groups upon oxidation of the bacterial membrane of 1700 cm-1 and 890 cm-1, the presence of carboxymethylated ether groups around 1020 cm-1, the elongation of OH groups of about 1318 cm-1 and the stretching of the CH bonds at the CH2 and CH3 groups at 2898 cm-1. Considering the values of total negative charge measured by potentiometric titration, we expect the highest adsorption capacity for 4CMC4CNF + CA (Q / m = 1.0675 mmol / g) and the lowest for BCoxd (Q / m = 0.2094 mmol / g). Membranes that are more negatively charged will, as a result, have a more positively charged dye adsorbed. In addition to the membrane charge, an important factor for dye adsorption is the structure of the membrane, which is evident from micrographs. The results of the confocal optical microscopy images revealed that they are the most fibrous 4CMC4CNF + CA membranes, which can be concluded to have the highest adsorption potential due to the larger active surface.
At the conclusion of the experimental work, we found that the colored solution was almost completely discolored, which means that the separation of the cationic dye from the aqueous medium was successful. CMC / CNF based membranes were 100% efficiently removed by the anthraquinone dye, while 24.3% were effectively removed by BC and 23.6% by BCoxd. The difference in BC-based membranes was minimal. Azo dye adsorbed the membranes slightly worse, with about 7-9% CMC / CNF based membranes and 5.57% BC and 7.33% BCoxd membranes. The membranes based on 4CMC4CNF + CA were shown to be the most effective in both cases. After all the analyzes performed, we can conclude that the most effective adsorbent of the selected cationic dyes is 4CMC4CNF + CA membranes, followed by 1CMC7CNF + CA, BCoxd and BC.|