Comparative Investigations on Optimum Polymerization Conditions for the Synthesis of a Sustainable Poly(Lactic Acid)

The development of synthetic biodegradable polymers using solvent free polymerization has a unique potential to be used as sustainable polymers in biomedical applications. The aim of this work was to synthesize and characterize a sustainable class of poly(lactic acid) (PLA) under different operating conditions via direct polycondensation of lactic acid (LA). Several parameters were tested including the absence of solvents and catalysts on the polymerization, in addition to polymerization temperature and time. Polymerization conditions were evaluated using response surface method (RSM) to optimize the impact of temperature, time, and catalyst. Results showed that molecular weight (M_w) of PLA increased with increasing polymerization time. Highest M_w of 28.4 kD with relatively a broad polydispersity 1.9 was achieved at polymerization temperature 170?°C at 24 h in the free solvent polymerization. This led to a relevant inherent viscosity of 0.37 dl/g. FTIR spectra exhibited a disappearance of the characteristic peak of the hydroxyl group in LA at 3482 cm^?1 by increasing the intensity of carbonyl group. The ¹H nuclear magnetic resonance (NMR) exhibited the main chain at 5.22 ppm and the signal of methyl proton at 1.61 ppm as well as a signal at 4.33 and 1.5 assigned to the methane proton next to the terminal hydroxyl group and carboxyl group respectively. Meanwhile, the PLA synthesized with a catalyst [Sn(Oct)₂] in a free solvent demonstrated comparatively high thermal transition properties of glass transition, melting, and crystallinity temperatures of 48, 106, and 158?°C, respectively. These results are of significant interest to further expand the use of PLA in biomedical applications.     

Biosynthesis and Characterization of Poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) from Bacillus cereus S10

The biodegradable and biocompatible copolymer poly-(3-hydroxybutyrate-co-5 mol% 3-hydroxyvalerate), poly-(3HB-co-5 mol% 3HV), was synthesized by Bacillus cereus S10 and the highest yield was determined as 69.91 % at pH 7 and 30 °C after 48 h of incubation using a glucose as the sole carbon source. Poly-(3HB-co-5 mol% 3HV) was purified from bacterial biomass using chloroform. FTIR analysis showed absorption bands at 1,723, 1,274, 1,373, 1,453, 2,932 cm^?1 corresponding to C=O, C–O stretching, CH₃, –CH₂ and –CH groups, respectively. ¹H-NMR and ¹³C-NMR analysis confirmed that the copolymer was composed of 95 mol% of 3-hydroxybutrate and 5 mol% of 3-HV monomeric units. Poly-(3-HB-co-5 mol% 3HV) was used for nanoparticles preparation. The diameter of nanoparticles was 202 nm.     

Synthesis and Properties of Polyesters from Waste Grapeseed Oil: Comparison with Soybean and Rapeseed Oils

The aim of this study was to investigate the application of grapeseed oil, a waste product from the wine industry, as a renewable feedstock to make polyesters and to compare the properties of these materials with those derived from soybean and rapeseed oils. All three oils were epoxidized to give renewable epoxy monomers containing between 3.8 and 4.7 epoxides per molecule. Polymerisation was achieved with cyclic anhydrides catalysed by 4-methyl imidazole at 170 and 210 °C. Polymers produced from methyl tetrahydrophthalic anhydride (Aradur917^®) had greater tensile strength and Young’s Modulus (tensile strength = 12.8 MPa, Young’s Modulus = 1005 MPa for grapeseed) than methyl nadic anhydride (MNA) derived materials (5.6 and 468 MPa for grapeseed) due to increased volume of MNA decreasing crosslink density. Soybean and grapeseed oils produced materials with higher tensile strength (5.6–29.3 MPa) than rapeseed derived polyesters (2.5–3.9 MPa) due to a higher epoxide functionality increasing crosslinking. T _g’s of the polyesters ranged from ?36 to 62 °C and mirrored the trend in epoxide functionality with grapeseed producing higher T _g polymers (?17 to 17 °C) than soybean (?25 to 6 °C) and rapeseed (?36 to ?27 °C). Grapeseed oil showed similar properties to soybean oil in terms of T _g, thermal degradation and Young’s Modulus but produced polymers of lower tensile strength. Therefore grapeseed oil would only be a viable substitute for soybean for low stress applications or where thermal properties are more important.     

Qualitative and Quantitative Analysis of Lignin Produced from Beech Wood by Different Conditions of the Organosolv Process

Lignins in general have been extensively studied, while beech wood lignin in particular is rarely researched. In the present work, Organosolv isolated lignin from beech wood (OBL) has been characterized. The isolation was done by two methods: (a) by using sulfuric acid at 170 °C and a reaction time of 120 min and (b) at a temperature of 180 °C for 240 min. A range of analytical methods were applied including elemental analysis, FT-IR, UV–Vis, ³¹P NMR, SEC, Pyrolysis-GC/MS and HPLC to gain information about establish the purity, structure, molecular weight, thermal behavior and to determine carbohydrate residues according to the NREL protocol. FT-IR and UV–Vis spectra of OBL revealed expected typical absorptions for lignins. NREL analysis presented a carbohydrate-free lignin fraction which has not been achieved to date. TGA and DSC are used to study the thermal behavior of the isolated lignins and showed a relatively low glass transition temperatures (T_g: 123 °C) and decomposition temperatures of 348 and 381 °C. The pyrograms generated from the pyrolysis–GC/MS at 550 °C consisted mainly of fragments of syringyl, guaiacyl and hydroxyphenyl units, thereby confirming the results of the NMR analysis. Our findings support Organolsolv as an efficient method to isolate pure lignin fractions from beech wood with practical value in industry.     

Cardanol Polymerization Under Acid Conditions By Addition And Condensation Reactions

Cashew nut shell liquid (CNSL) is a byproduct of the cashew nut industry and consists predominantly of phenolic compounds that have an side chain with different degrees of unsaturation. Cardanol, one of these components, is biodegradable and widely available. Studies have revealed several polymerization reactions involving cardanol. However, the mechanisms and detailed structures of polymerization reactions have not been explored, although the final product shows different applications. In this work, we evaluated the mechanism and the products structure of the reaction of cardanol with: (i) boron trifluoride diethyl etherate (BF₃O(CH₂CH₃)₂), and (ii) formaldehyde. The characterizations were performed by FTIR, ¹H NMR, SEC and TGA. The results show that the reaction of cardanol with aldehyde produces the expected like-comb structure with a long hydrocarbon pendent chain. Nevertheless, the reaction of cardanol with BF₃O(CH₂CH₃)₂ can exhibits a more complex structure since it was identified aromatic ring linkages, besides the expected polymerization through C=C.     

Biodegradability of Epoxidized Soybean Oil Based Thermosets in Compost Soil Environment

In this study, bio-thermoset from epoxidized soybean oil (ESO) was prepared in the presence of methylhexahydrophthalic anhydride curing agent and 2-ethyl-4-methylimidazole catalyst. The crosslink densities of the synthesized ESO are ranged from 0.109 × 10^?3 to 0.308 × 10^?3 mol/cm³. The ESO bio-thermosets were exposed to the soil-burial test for 8 months. Weight change and morphology of the degraded ESO specimens were assessed. It was found that the weight loss of ESO was governed by the materials compositions, crosslink density and the soil-burial exposure time. The 3 mm thickness ESO bio-thermosets with crosslink density of 0.109 × 10^?3 mol/cm³ had fully biodegraded after soil-burial for 6 months. In addition, 16S rDNA sequencing was carried out to identify the soil microorganisms. It was suggested that Comamonas sp., Bacillus sp., Streptomyces sp. and Acinetobacter sp. are the possible soil microbes that degrade the ESO bio-thermosets in the compost soil environment.     

Catalytic gasification of tars from a dumping site

The work deals with catalytic gasification, pyrolysis and non-catalytic gasification of tar from an industrial dumping site. All experiments were carried out in a vertical stainless steel gasification reactor at 800 °C. Crushed calcined dolomite was used as the gasification catalyst. Parameters such as addition of water and air, and the influence of the catalyst in regard to the composition of the process gas were investigated. The catalytic gasification experiment in the steady state produced process gas with the composition: 56 % of H₂, 9 % of CO, 11 % of CH₄ and 12 % of CO₂ (mol.%). Concentration of the C₂ fraction was lower than 1 mol.%. Volume flow of air was later changed from 120 to 230 ml min^?1 reducing the amount of hydrogen to 51 mol.% and that of methane to 10 mol.%. Process gas created in a non-catalytic gasification process contained 26–30 mol.% of methane, 13–15 mol.% of carbon monoxide and 15–17 mol.% of the C₂ fraction and lower amounts of hydrogen (20 mol.%) and carbon dioxide (2–3 mol.%). The highest apparent conversion of tar was reached in the catalytic gasification processes. A higher rate of catalyst deactivation can be observed when water or air is not added.     

Arsenic Removal from Dilute Solutions by High Surface Area Mesoporous Iron Oxyhydroxide

Mesostructured iron oxyhydroxide (FeO _x ) and iron oxyhydroxide–phosphate (FeO _x P) composites were organized using dodecylsulfate surfactant as a template. X-ray diffraction studies depicted a lamellar structure of the product. Ion exchange and solvent extraction methods were employed for the removal of the surfactant. Carboxylate ions exchanged lamellar type mesostructured material reorganized to a wormhole-like mesoporous material when heated under N₂ atmosphere. Surfactant was completely removed by carboxylate ions as observed by the Fourier transform infrared spectra. High surface area acetate-exchanged FeO _x (230 m² g^?1) was obtained after the surfactant removal from the composite (2.8 m² g^?1). Surface area of acetate-exchanged FeO _x P was the highest (240 m²g^?1) after the removal of the surfactant. Local structure of iron species of FeO _x was investigated by X-ray absorption fine structure spectroscopy. Further, Fe···Fe bond appeared at 3.21–3.25 Å with coordination number 2–3, showing a high degree of un-saturation of Fe···Fe bonds. As compared with bulk iron oxyhydroxide and iron-intercalated montmorillonite, the mesoporous iron materials were highly effective for arsenic removal from low concentrations of aqueous solutions. Furthermore, mesoporous iron materials were stable in aqueous phase.     

Potential of biogas production from mixed leaf and food waste in anaerobic reactors

Anaerobic digestion of mixed leaf (MLW) and food wastes (FW) was used to explore the potential use of MLW as an accelerator for FW digestion in two parts for biogas production and as a waste management option in a university community. The effects of the single substrate of FW, co-digestion, ratio of MLW and FW (3:2 and 2:3) and ratio of waste feed to inoculum: F/I (0.1 and 0.4), and feeding frequency (every other day and every 2 days) were evaluated in two neutralized anaerobic reactors. The results showed that different mixture ratios with the same F/I ratio were the major factor on biogas (39.87 m³/kg VS_added) and CH₄ yield (25.99 m³/kg VS_added), including %COD removal (84.50%). Co-digestion had the same effect as F/I on biogas production. Only FW provided the lowest biogas and CH₄ yield. The use of a MLW:FW 2:3, F/I 0.4 mixture with every 2 days feeding provided higher biogas production and %COD removal than with every other day feeding. Two neutralized anaerobic reactors were suitable for digestion with a high F/I, and a wider interval feeding. This finding affirms the possibility of biogas production using MLW as the co-substrate with FW, as opposed to using FW alone.     

Stabilization of sewage sludge in the presence of nanoscale zero-valent iron (nZVI): abatement of odor and improvement of biogas production

The potential benefits of nanoscale zero-valent iron (nZVI) on sludge stabilization, either the abatement of odor or the improvement of biogas production, were investigated in this study. Two commercial-grade microscale iron powders were also utilized for comparison. Adding 0.10 wt% of nZVI in sludge during anaerobic incubation significantly reduced the concentration of H₂S in biogas by 98.0 % (96.2–98.9 %), probably attributed by reactions between sulfides and the neo-formed hydrous Fe(II)/Fe(III) oxides layer at the surface of ZVI nanoparticles. Meanwhile, the percentage of P in bioavailable fractions decreased from 76.8 to 52.5 %, possibly due to the formation of vivianite [Fe₃(PO₄)₂]. Furthermore, 0.10 wt% of nZVI in anaerobic digestion for 17 days enhanced the concentration of CH₄ in biogas by 5.1–13.2 % and improved the production of biogas and methane by 30.4 and 40.4 %, respectively. The amendment of iron nanoparticles during anaerobic digestion can not only effectively reduce H₂S in biogas, but also potentially boost methane production significantly.     

Quantification of methane emissions from full-scale open windrow composting of biowaste using an inverse dispersion technique

An inverse dispersion technique in conjunction with Open-Path Tunable-Diode-Laser-Spectroscopy (OP-TDLS) and meteorological measurements was applied to characterise methane (CH₄) emissions from an Austrian open-windrow composting plant treating source-separated biowaste. Within the measurement campaigns from July to September 2012 different operating conditions (e.g. before, during and after turning and/or sieving events) were considered to reflect the plant-specific process efficiency. In addition, the tracer technique using acetylene (C₂H₂) was applied during the measurement campaigns as a comparison to the dispersion model. Plant-specific methane emissions varied between 1.7 and 14.3 g CH₄/m³d (1.3–10.7 kg CH₄/h) under real-life management assuming a rotting volume of 18,000 m³. In addition, emission measurements indicated that the turning frequency of the open windrows appears to be a crucial factor controlling CH₄ emissions when composting biowaste. The lowest CH₄ emission was measured at a passive state of the windrows without any turning event (“standstill” and “sieving of matured compost”). Not surprisingly, higher CH₄ emissions occurred during turning events, which can be mainly attributed to the instant release of trapped CH₄. Besides the operation mode, the meteorological conditions (e.g. wind speed, atmospheric stability) may be further factors that likely affect the release of CH₄ emissions at an open windrow system. However, the maximum daily CH₄ emissions of 1 m³ rotting material of the composting plant are only 0.7–6.5% of the potential daily methane emissions released from 1 m³ of mechanically–biologically treated (MBT) waste being landfilled according to the required limit values given in the Austrian landfill ordinance.     

Dynamic studies on lead volatilization from CaO–SiO2–Al2O3 molten slag under N2–CO–CO2, N2–HCl and N2–H2S gas atmospheres

Dynamic studies on the volatilization of lead from CaO–SiO₂–Al₂O₃ molten slags were conducted in a lab-scale melting furnace from 1623 to 1773 K under different mixed gas atmospheres of CO 0.05–0.3 atm to CO₂ 0–0.3 atm to N₂ (balance), HCl 1.7 × 10^?3–6.7 × 10^?3 atm to N₂ (balance), and H₂S 3.0 × 10^?4 to 1.7 × 10^?3 atm to N₂ (balance). The slag samples consisted of the mixed powders of 20–50 wt% CaO, 30–60 wt% SiO₂, and 10–40 wt% Al₂O₃, containing 2000 ppm PbO.Results showed that the rates of volatilization of lead from the CaO–SiO₂–Al₂O₃ molten slags under the N₂–CO–CO₂, N₂–HCl, and N₂–H₂S gas atmospheres were higher than those under the simulated air (N₂–O₂), which increased with CO, HCl, and H₂S partial pressures. At \(p_{{HCl}}\)  =  \(p_{H_{2}S}\)  = 1.7 × 10^?3 atm, the apparent rate constants for the volatilization of lead under the N₂–H₂S and N₂–HCl gas atmospheres were nearly equal, which increased with a rise in temperature. Results also showed that the rate of volatilization of lead from the molten slag decreased drastically with the increasing viscosity of the molten slag, in the viscosity range lower than 3 Pa s. Consequently, the volatilization of lead from the CaO–SiO₂–Al₂O₃ molten slag was significantly influenced by CO, HCl, and H₂S partial pressures and by the viscosity of the molten slag.     

Identification of PM10 Sources in a Mediterranean Island

Due to the dry Mediterranean climate in Cyprus, particulate matter is resuspended from soils and other surfaces. From November 2002 to August 2003, gravimetric PM₁₀ measurements were carried out at three characteristic sites (traffic, residential and rural). A significant seasonal trend with high winter concentrations was observed at the traffic site. Special events, e.g. long-range transport of Sahara dust storms, were recorded over traffic, residential and rural areas in the order of six to eight events per year, with a major frequency in summer and spring periods. This contributes to the increase of 24-h EU limit value exceedances for PM₁₀ at the three investigated sites. The origin of the PM₁₀ load was determined by enrichment factors based on analyses of the local soil deposition at the investigated sites. Furthermore, positive matrix factorisation modelling was applied to find the sources of PM₁₀. Results indicate that the major emission sources affecting the PM₁₀ load were mineral soil, sea salt, road dust, oil combustion, secondary pollutants and gasoline vehicles. The natural contribution (local mineral soil and sea salt) at the three sites was in the range of 7–9 μg m^?3 in PM₁₀. Besides the Sahara dust storms and natural background concentrations, the vehicular pollution was found as the largest contributor (12–14 μg m^?3) to PM₁₀ load at the traffic site.     

Green Synthesis and Physical Properties of poly(Vinyl Alcohol) Maleated in an Aqueous Solutions

The objective of this work was to synthesize maleated poly(vinyl alcohol) (PVAM) in aqueous solution through esterification, and to seek near optimal degree of grafting and crosslinking. The effects of maleic anhydride (MA) content on the properties of PVAM were investigated. The experimental observations included characterizations by ATR–FTIR and thermo gravimetric analyses (TGA), and determinations of grafting ratio, dynamic viscosity, and swelling ratio. The percentage degree of grafting, dynamic viscosity, and particle size increased with MA content, while the swelling ratio decreased due to copolymerization of poly(vinyl alcohol) (PVA) and MA. The peaks at 945 and 918 cm^?1 in the spectrum of PVA indicated the presence of carboxylic groups, while in the spectrum of PVAM only one peak at 920 cm^?1 indicated presence of carboxylic groups, due to copolymerization of PVA and MA. Moreover, the thermal stability of PVA-g-MA was enhanced as observed from TGA. The results suggest 7:3 PVA/MA mass ratio as near optimal for PVA-g-MA.     

The impact of pretreatment and inoculum to substrate ratio on methane potential of organic wastes from various origins

Biochemical methane potentials (BMP) of two different substrates from macroalgae (MA) and market place wastes (MPW) were investigated using anaerobic granulated sludge from food industry with different ratios of substrate to inoculum (S/X). The substrates were used as MA only, MPW only, MA–MPW mixture, pretreated MA, and pretreated MA–MPW mixture. Research involved investigation of the effects of parameters such as temperature (35, 45, and 55 °C), substrate to inoculum ratio (S/X = 0.5, 2.0, 4.0, and 6.0 as g VS_substrate/g VS_inoculum), and the type of pretreatment (by microwave, thermal, and ultrasonic) on BMP. BMP assays were performed for all substrates. The highest cumulative biogas production (and BMP) were obtained for MA only at an S/X ratio of 4.0 g VS/g VS as 357 L_biogas/kg VS (197 L CH₄/kg VS) and 33 L_biogas/kg VS (17 L CH₄/kg VS), respectively, at 35 and 55 °C. For pretreated substrates, the highest cumulative biogas production and BMP were observed as 287 L_biogas/kg VS and 146 L CH₄/kg VS using pretreated macroalgae at 35 °C. Results suggested that MA only and MA–MPW mixtures are suitable substrates for biogas production. It is also concluded that any type of pretreatment has adverse effects on biogas and methane productions.     

Quantifying methane oxidation in a landfill-cover soil by gas push–pull tests

Methane (CH₄) oxidation by aerobic methanotrophs in landfill-cover soils decreases emissions of landfill-produced CH₄ to the atmosphere. To quantify in situ rates of CH₄ oxidation we performed five gas push–pull tests (GPPTs) at each of two locations in the cover soil of the Lindenstock landfill (Liestal, Switzerland) over a 4 week period. GPPTs consist of the injection of a gas mixture containing CH₄, O₂ and noble gas tracers followed by extraction from the same location. Quantification of first-order rate constants was based upon comparison of breakthrough curves of CH₄ with either Ar or CH₄ itself from a subsequent inactive GPPT containing acetylene as an inhibitor of CH₄ oxidation. The maximum calculated first-order rate constant was 24.8 ± 0.8 h^?1 at location 1 and 18.9 ± 0.6 h^?1 at location 2. In general, location 2 had higher background CH₄ concentrations in vertical profile samples than location 1. High background CH₄ concentrations in the cover soil during some experiments adversely affected GPPT breakthrough curves and data interpretation. Real-time PCR verified the presence of a large population of methanotrophs at the two GPPT locations and comparison of stable carbon isotope fractionation of CH₄ in an active GPPT and a subsequent inactive GPPT confirmed that microbial activity was responsible for the CH₄ oxidation. The GPPT was shown to be a useful tool to reproducibly estimate in situ rates of CH₄ oxidation in a landfill-cover soil when background CH₄ concentrations were low.     

Synthesis and Properties of Poly(d,l-lactide-co-p-dioxanone) Random and Segmented Copolymers

Two different polymerization routes, one-step and two-step bulk ring-opening polymerizations of d,l-lactide (LA) and p-dioxanone (PDO) monermers using stannous octoate [Sn(Oct)₂]/n-dodecanol as the initiating system, were employed to synthesize poly(d,l-lactide-co-p-dioxanone) P(LA-co-PDO) random and segmented copolymers with different compositions and chain microstructure. For the two-step copolymers, the average sequence lengths of the lactidyl (L_LA) and dioxanyl (L_PDO) units calculated from the ¹H-NMR spectra were much longer than those values for the one-step copolymers with the same LA/PDO feed ratio. Corresponding to this difference in microstructure, the two-step copolymers were semi-crystalline even when the PDO content was as low as 14.5 mol%, while the one-step copolymers were completely amorphous with PDO content below 60.6 mol%. However, irrespective of polymerization route, both types of copolymers displayed a single glass transition temperature that was in a linear relation with composition. The decrease of maximum decomposition temperature of the copolymers was in accordance with the decrease of L_PDO value. The mechanical and degradation properties of the copolymers were significantly affected by both the polymerization route and the chemical composition as well. In conclusion, the properties of P(LA-co-PDO) copolymers could be adjusted conveniently to meet specific applications by changing the composition and microstructure of the copolymers via different polymerization routes.     

Effect of Nano-SiO<Subscript>2</Subscript> and Bark Flour Content on the Physical and Mechanical Properties of Wood–Plastic Composites

The aim of this study is to evaluate the impact of nano-SiO₂ and bark flour (BF) on the natural fiber–plastic composites engineering properties made from high density polyethylene (HDPE) and beech wood flour (WF). For this purpose, WF and BF in 60 mesh size and weight ratio of (50, 0 %), (30, 20 %), (10, 40 %) and (0, 50 %) respectively were mixed with HDPE. In order to increase the interfacial adhesion between the filler and the matrix, the maleic anhydride grafted polyethylene was constantly used at 3 wt% for all formulations as a coupling agent. The nano-SiO₂ particles with weight ratio of 0, 1, 2, and 4 % were also utilized to enhance the composites properties. The materials were mixed in an internal mixer (HAAKE) and then the bark and/or wood–plastic composite samples were made utilizing an injection molding machine. The physical tests including water absorption and thickness swelling, and mechanical tests including bending characteristics and un-notched impact strength were carried out on the samples based on ASTM standard. The results indicated that as the BF content increased in the composite, mechanical and physical properties were reduced, but the given properties were increased with the addition of nano-SiO₂. The addition of nano-SiO₂ had a negative impact on the physical properties, but when it was up to 2 %, it increased the impact strength.     

Laccase-Assisted Grafting of Acrylic Acid onto Lignin for its Recovery from Wastewater

The acrylic acid (AA) in the wastewater from paint manufacturing could be recovered by grafting to lignosulfonate in the presence of laccase and tert-butyl hydroperoxide (t-BHP). The low concentration of t-BHP did not inhibit the laccase activity, but improved the radical formation on lignin by laccase reaction, then initiated AA polymerization on lignin. The results showed laccase took a significant role for AA grafting to lignin. 94 % of AA could be polymerized on lignin by laccase/t-BHP, while only 32 % of AA was grafted on lignin with the same condition without laccase. The ratio of lignin to acrylic acid also affected AA recovery, and higher concentration of acrylic acid led to high recovery rate of AA. In this reaction system, the suitable range of temperature was 30–40 °C for the chemo-enzymatic reaction. The AA grafted on lignin could be precipitated by calcium ion and recovered.     

A Study of the Photocatalytic Oxidation of Humic Acid on Anatase and Mixed-phase Anatase–Rutile TiO2 Nanoparticles

In this study, slurry photocatalytic oxidation process was investigated for natural organic matter removal from aqueous humic acid solutions by using different titanium dioxide (TiO₂) under UV-A irradiation. Bench scale experimental studies were conducted at different humic acid concentration at the range of 10–50 mg/L and different pH. Anatase and mixed-phase anatase–rutile TiO₂ nano particles used in the photocatalytic reactor. The results were evaluated in terms of the parameters that are specific to organic matter content such as dissolved organic carbon concentration, ultraviolet absorbance at 254 nm (UV₂₅₄), specific ultaviolet absorbance at 254 nm, and color (VIS₄₀₀). It was observed that increasing humic acid concentration decreases photocatalytic degradation efficiency. The reactivity of the mixed-phase anatase–rutile (Degussa P-25) TiO₂ was greater than individual anatase particles and the highest efficiency was observed at pH 3 for anatase TiO₂.