Reference Lignin source Catalyst Reaction conditions
MacHado et al. [42 ] Peroxyformic acid lignins from eucalyptus grandis wood (EL1) EL1 + sodium borohydride TiO2 and H2 O2 Lignin concentration: 0.25 mg/mL, °C, pH 11, UV Vis radiation nm, 400 W mercury lamp, cylindrical Pyrex glass reactor, constant oxygen bubbling
Ksibi et al. [47 ] Water soluble lignin obtained from black liquor TiO2 -P25 (Degussa) Lignin concentration: 90 mg/L, °C, pH 8.2, UV-radiation nm, pyrex reactor open to air, Philips HPK 125 W lamp
Kansal et al. [48 ] Lignin from wheat straw kraft digestion TiO2 -P25 (Degussa) and ZnO Lignin concentration: 10–100 mg/L in 100 mL, ZnO catalyst dose (0.5–2.0 g/L), pH of the solution (pH 3–11), solar illumination, oxidant concentration: M to M, thin bed film slurry pond reactor, oxidant: sodium hypochlorite solution (4% available Cl2 )
Dahm and Lucia [49 ] Whitewater from industrial process water that exits in paper machines Fischer Scientific rutile TiO2 Lignin concentration: 40 mg/L in 500 mL batch reactor, °C–42°C, Rayonet photochemical chamber, 16 VWR 8-W black light, phosphor (350-nm) lamps, constant oxygen bubbling, power of illumination: 128 to 64 W, light intensity: 223–445 mW/cm3
Portjanskaja and Preis [50 ] Lignin, purchased from Aldrich TiO2 P25-N (Degussa) Lignin concentration: 100 mg/L, pH 8, batch reactor system, reactor open to air, Phillips TLD 15 W/05 low-pressure luminescent mercury UV-lamp, UV-radiation nm, power density of irradiation = 0.7 mW/cm2 , visible light source
Tanaka et al. [51 ] Lignin from coniferous wood TiO2 (TiO2 —TP-2 of Fujititan) Lignin concentration: 0.003 to 0.03%, UV-radiation nm, cylindrical reaction vessel
Tonucci et al. [33 ] Ca2+ and lignin derivatives TiO2 as Degussa P25 + polyoxometalates (POM), H2 O2 Open quartz tubes (20 mL) reactor, °C, 1 atm, multirays of ten UV lamps of 15 W power each, UV-radiation nm
Miyata et al. [24 ] Picea glehnii wood flour TiO2 /polyethylene oxide (PEO) Reactor: open petri dish, °C, h, 400 W mercury lamp
Shende et al. [17 ] Kraft lignin TiO2 -ZnO-ZrO2 Lignin concentration: 1 mg/mL in 10 mL, 250 W Xenon lamp and AM 1.5 G lamp filter, power density of irradiation: 100 mW/cm2 , solar lamp simulator
Tian et al. [52 ] and Pan et al. [53 ] Kraft lignin from black liquor Ta2 O5 -IrO2 and PbO2 thin film TiO2 nanotube/PbO2 Lignin concentration: 30% (w/w), UV-radiation nm, min, power density of irradiation: 20 mW/cm2 , blue wave TM50 AS UV spot lamp, EG&G 2273 potentiostat/galvanostat to apply current, Ti/TiO2 NT/PbO2 electrode as working electrode and Pt coil as outer electrode and Ag/AgCl as reference electrode
Awungacha Lekelefac et al. [54 ], [55 ] Lignin sulfonate from paper waste water TiO2 as Degussa P25 TiO2 from sol-gel process of TiOSO4 , TTIP Lignin concentration: 500 mg/L in 200 mL, Osram Planon light source, irradiance: 30–40 W/m2 , UV-radiation λ : 280–420 nm, h, reactor open to air, recirculation system, flow rate 22.5 mL/min