Table 2.
Current development in processes used in dye removal.
| Process | Current Development | References |
|---|---|---|
| Adsorption | Synthesizing of new, efficient, nature-based, or waste-originating adsorbents, kinetic, equilibrium and thermodynamic studies on biosorption | [42,43,44,45,46] |
| Coagulation/flocculation | Synthesizing of new, efficient, nature-based, or waste-originating coagulants and acceleration of sedimentation by magnetic field | [47,48,49,50,51,52] |
| Electro-coagulation | Ultra-sound assistance, nanofilms on cathodes and solar power usage | [53,54,55,56,57,58] |
| Electrochemical oxidation | Air-diffusion cathodes, new materials and coatings of electrodes, membrane anode and electro-peroxone process | [59,60,61,62,63,64] |
| Membrane filtration | Novel membrane materials, with addition of graphene, stabilization of membranes by biomacromolecules | [65,66,67,68,69,70] |
| Ozonation | Catalyst addition, enhancement by ultrasound and hydrodynamic cavitation | [71,72,73,74,75] |
| O3/UV | Photocatalytic membranes | [76] |
| O3/H2O2 | Proposal of the degradation mechanism, enhancement by electrolysis, heterogenous catalyst addition | [77,78,79] |
| UV/H2O2 | Measurements of cytotoxicity, mutagenicity and phytotoxicity changes, proposal of degradation mechanism, comparison of different UV sources | [80,81,82,83,84,85] |
| Photocatalytic oxidation | Synthesizing nanoparticles, efficient under visible light or difunctional catalysts, green methods of catalyst synthesis | [86,87,88,89,90,91] |
| Fenton | Fenton-like heterogenous catalysts enabling dye degradation in a wide range of pH, among the others zero-valent iron catalysts, green or one-spot synthesis of catalysts, fixed bed reactor application, implementation of sulphate radical anions | [92,93,94,95,96] |
| Photo-Fenton | Fenton-like heterogenous catalysts enabling dye degradation under visible light, waste-originating catalysts, proposal of degradation mechanism | [97,98,99,100,101,102] |
| Electro-Fenton | Kinetics and cost analysis, synthesizing of nanocomposite electrodes, air-diffusion cathode, proposal of mechanism and degradation pathways, novel orbiting electrodes reactor and recirculation flow-through reactor | [103,104,105,106,107,108] |
| Bacterial treatment | Isolation of new strains or consortia from activated sludge, oxidation ditch, palm oil mill effluent or desert soil, alkali-, halo- and thermophilic strains implementation, consortium with algae, bacteria immobilization, co-substrate addition, proposal of mechanisms, pathways genome and transcriptome analysis | [109,110,111,112,113,114,115,116,117,118,119] |
| Fungal treatment | Implementation of microbial consortium (e.g., yeast consortium with ability of lignin valorization dye treatment and biodiesel production), fungi immobilization, isolation of new strains from plant roots or effluent site | [120,121,122,123,124,125,126,127,128,129,130] |
| Enzyme treatment | Optimization of enzyme production, enzyme immobilization, metabolites and toxicity assessment | [131,132,133,134,135,136] |
| Algal treatment | Immobilization, co-contaminant influence on dye biodegradation, genetic modification of algae and cyanobacteria, graphene oxide addition and lipid production | [137,138,139,140,141] |
| Activated sludge, anaerobic sludge | Granule formation (anaerobic core with aerobic shell), metagenomic analysis in anaerobic MBR, addition of resuscitation-promoting factors, integration of anaerobic and aerobic reactors, addition of halotolerant yeast and magnetic field | [142,143,144,145,146,147,148,149,150] |
| Biofilm | Application of new biocarriers, co-substrate addition, kinetic analysis and process optimization in moving bed biofilm reactor, biomass acclimatization and optimization of anoxic/aerobic sequencing batch moving bed bioreactors | [151,152,153,154,155] |