Coagulation with polymers for nanofiltration pre-treatment of highly concentrated dyes: A review

Abstract

Water scarcity and strict legislation make water reuse in dye related industries like textile and leather become more important. Among the different types of dyes, soluble dyes are the most problematic. Nanofiltration was vital for the treatment of dye wastewater but the major limitation is fouling. Coagulation/flocculation can be effective to enhance nanofiltration performance towards water reuse and minimisation of fouling. The selection of the coagulant type (metal or polymer) and dosages are very critical in this technique. Factors that improved the coagulation were studied in detail and suitable metal coagulants were presented. Cationic, anionic and natural polymers as flocculant aids were also reported for successfully enhancing dye removal. Adding a suitable type of metal coagulant-polymer at an optimum dosage and mixing conditions increases the dye removal at a wider range of operating pH and reduces the production of sludge. In-depth studies on the effect of metal coagulant-polymer on membrane fouling are still lacking and visualisation techniques might be helpful in this regard.

Nanofiltration of hazardous Congo red dye: Performance and flux decline analysis

“…It can be seen from Fig. 4 that the high fouling at pH 7 might be due to the larger dye aggregates attracted by the positive charge on the membrane surface leading to pore blockage [33,34]. Also, low electrostatic repulsion (in comparison to that under pH 9) between the dye molecule and membrane surface might cause the penetration of dye molecules into the membrane pores.…”

Application of AzollaFiliculoides Biomass in Acid Black 1 Dye Adsorption from Aqueous Solution

“…Therefore, the treatment of textile effluent and especially dye removal is necessary. It has been reported that the acid and reactive dyes are resistant against the conventional treatment methods (5,9). Consequently, the many techniques such as membrane separation, electrochemical, flocculation-coagulation, reverse osmosis, ozone oxidation, biological treatments, etc.…”

“…The textile industries are known as significant dye consumer and major colorful wastewater producer (3). The dyes are defined as organic molecules with complex aromatic structure (4,5). Owing to their properties, the dyes can create an esthetic issues and many risks to public health (6,7).…”

New treatment at source approach using combination of microfiltration and nanofiltration for dyeing effluents reuse

“…Textile wastewater reuse is strongly related with membrane processes, especially nanofiltration (NF) process which has been widely studied (Tang and Chen 2002;Wenzel et al 1996;Zahrim et al 2011). Because of the reduced pore size of NF membrane (almost 10 -9 m) against the important pollutant charge of the dyeing effluent, membrane fouling represents the major limitation for the use of single NF treatment.…”

“…Coagulation/ flocculation (C/F) can be also used prior to Rierra-Torres et al (2010) found that the combination of C/F and NF almost provided more than 90 % of color retention for different dyes solutions. Zahrim et al (2011) studied the potential of coagulation flocculation to minimize the fouling of NF membrane during the treatment of highly concentrated dyes solutions. Electro-coagulation is also a new technology for the treatment of textile effluents which can be combined with NF for wastewater reuse; Aouni et al (2009) observed that following this approach, a color removal of more than 99 % was mostly obtained.…”