Adsorptive removal of phosphate from aqueous solutions using iron oxide tailings

This study explored the feasibility of utilizing industrial waste iron oxide tailings for phosphate removal in laboratory experiments. The experimental work emphasized on the evaluation of phosphate adsorption and desorption characteristics of the tailing material. The adsorption isotherm, kinetics, pH effect and desorption were examined in batch experiments. Five isotherm models were used for data fitting. The three-parameter equations (Redlich-Peterson and Langmuir-Freundlich) showed more applicability than the two-parameter equations (Freundlich, Langmuir and Temkin). A modified equation for calculation of the separation factor using the Langmuir-Freundlich equation constants was developed. The initial phosphate adsorption on the tailings was rapid. The adsorption kinetics can be best described by either the simple Elovich or power function equation. The phosphate adsorption on the tailings tended to decrease with an increase of pH. A phosphate desorbability of approximately 13-14% was observed, and this low desorbability likely resulted from a strong bonding between the adsorbed PO(4)(3-)and iron oxides in the tailings. Column flow-through tests using both synthetic phosphate solution and liquid hog manure confirmed the phosphate removal ability of the tailings. Due to their low cost and high capability, this type of iron oxide tailings has the potential to be utilized for cost-effective removal of phosphate from wastewater.     

In vitro evaluation of cytotoxicity of engineered metal oxide nanoparticles

The recent advances in nanotechnology and the corresponding popular usage of nanomaterials have resulted in uncertainties regarding their environmental impacts. In this study, we used a systematic approach to study and compare the in vitro cytotoxicity of selected engineered metal oxide nanoparticles to the test organisms — E. coli. Among the seven test nano-sized metal oxides, ZnO, CuO, Al₂O_3, La₂O_3, Fe₂O_3, SnO₂ and TiO_2, ZnO showed the lowest LD₅₀ of 21.1 mg/L and TiO₂ had the highest LD₅₀ of 1104.8 mg/L. Data of ¹⁴C-glucose mineralization test paralleled the results of bacteria viability test. After regression calculation, the cytotoxicity was found to be correlated with cation charges (R² = 0.9785). The higher the cation charge is, the lower the cytotoxicity of the nano-sized metal oxide becomes. To the best of our knowledge, this finding is the first report in nanotoxicology.     

Preparation of DNA-adsorbed TiO2 particles — Augmentation of performance for environmental purification by increasing DNA adsorption by external pH regulation

We have previously developed a novel photocatalyst, DNA-attached titanium dioxide (DNA-TiO₂), useful for the recovery and decomposition of chemicals [Suzuki et al. Environ. Sci. Technol. 42, 8076, 2008]. Chemicals accumulated in DNA near the surface of TiO₂ and were degraded under UV light. The efficiency of their removal was dependent on the amount of DNA adsorbed on TiO₂, indicating the attachment of larger amounts of DNA to result in higher efficiency. In this study, we succeeded in improving the performance of DNA-TiO₂ by increasing the amount of DNA adsorbed by regulating the external pH. The adsorption of DNA by TiO₂ dramatically increased at pH2, to about fourfold that at other pH values (pH4-10). Repeating the process of DNA addition increased the adsorption further. The attached DNA was stable on the surface of TiO₂ at pH2-10 and 4-56 °C, the same as DNA-TiO₂ prepared at pH7. As the DNA-TiO₂ prepared at pH2 retained much DNA on its surface, chemicals (methylene blue, ethidium bromide, etc.) which could intercalate or react with DNA were effectively removed from solutions. The photocatalytic degradation was slow at first, but the final degradation rate was higher than for non-adsorbed TiO₂ and DNA-TiO₂ prepared at pH7. These results indicated that preparation of DNA-TiO₂ at pH2 has advantages in that much DNA can be attached and large amounts of chemicals can be concentrated in the DNA, resulting in extensive decomposition under UV light.     

Photocatalytic degradation of Acid Red 88 using Au-TiO(2) nanoparticles in aqueous solutions

Metal loaded semiconductors in general possess greater photocatalytic activity than pure semiconductors. Hence, with an attempt to achieve higher photocatalytic activity, Au-TiO₂ photocatalysts were prepared by deposition-precipitation method and used for the photocatalytic degradation of an azo dye (Acid Red 88; AR88). The materials were characterized by different analytical techniques. A possible mechanism for the photocatalytic degradation of AR88 by Au-TiO₂ in the absence and presence of other oxidizing agents (peroxomonosulfate (PMS), peroxodisulfate (PDS) & hydrogen peroxide (H₂O₂)) has been proposed. The extent of mineralization of the target pollutant was also evaluated using Total Organic Carbon (TOC) analysis.     

Release of phosphorous impurity from TiO2 anatase and rutile nanoparticles in aquatic environments and its implications

Phosphorus-bearing materials as an additive have been popularly used in nanomaterial synthesis and the residual phosphorus within the nanoparticles (NPs) can be of an environmental concern. For instance, phosphorus within pristine commercial TiO₂ NPs greatly influences the surface charge and aggregation behavior of the host TiO₂ in aquatic environments; however, it is unknown whether and how fast phosphorus is released. In this study, we focus on the phosphorus release kinetics from five types of TiO₂ NPs (i.e., 5, 10, and 50 nm anatase and 10 × 40, 30 × 40 nm rutile) under the influence of varying solution chemistries. The 50 nm anatase has the highest quantity of P (8.05 g/kg) and most leachable P dissolves within the first 2 h (i.e., 5.01 g/kg), which presents a potential pollutant source of P. Higher pH favors the phosphorus release (release order: pH 11.2 > pH 8.2 > pH 2.4), while variations in the environmentally relevant ionic strengths (0.01 M NaCl + 0.01 M NaHCO₃ and 0.04 M NaCl + 0.01 M NaHCO₃) and the presence of dissolved natural organic matter (10 mg/L) do not affect release rate greatly. X-ray Absorption Near Edge Structure results suggest that phosphate adsorbed on the pristine 50 nm anatase desorbs, and some dissolved phosphate again re-sorbs as a surface precipitate. The findings from this research may have important environmental implications such as accidental release of TiO₂ NPs and other nanomaterials that are synthesized using phosphorus containing chemicals as an ingredient.     

Greywater treatment by UVC/H2O2

Greywater treatment by UVC/H₂O₂ was investigated with regard to the removal of chemical oxygen demand (COD). A COD reduction from 225 to 30 mg l⁻¹ (overall removal of 87%) was achieved after settling overnight and subsequent irradiation for 3 h with 10 mM H₂O₂. Most of the contaminants were removed by oxidation since only 13% COD was removed by settlement.The removal of COD in the greywater followed a second-order kinetic equation, r = 0.0637[COD][H₂O₂], up to 10 mM H₂O₂. A slightly enhanced COD removal was observed at the initial pH of 10 compared with pH 3 and 7. This was attributed to the dissociation of H₂O₂ to O₂H⁻. The treatment was not affected by total concentration of carbonate (c_T) of at least 3 mM, above which operation between pH 3 and 5 was essential. The initial biodegradability of the settled greywater (as BOD₅:COD) was 0.22. After 2 h UVC/H₂O₂ treatment, a higher proportion of the residual contaminants was biodegradable (BOD₅:COD = 0.41) which indicated its potential as a pre-treatment for a biological process.     

Reduction of ClO2 demand by ClO2 oxidation and subsequent GAC filtration

The effective removal of soluble natural organic matter (NOM) during water treatment can significantly decrease the ClO(2) demand of processed water. This can be achieved through the oxidation and/or the removal of NOM. The purpose of the study was to examine the influence of ClO(2) oxidation and subsequent GAC filtration on the final ClO(2) demand of treated water. The study showed the ClO(2) demand to be strongly correlated with the abundance of high molecular fractions of NOM in treated water. As it was shown, this part of NOM was effectively removed during the GAC filtration. Moreover, the pre-treatment of water with ClO(2) considerably increased the total capacity of GAC filters for organic and inorganic (i.e. chlorites) oxidation by-products. Therefore, the oxidation of NOM molecules in conjunction with a very efficient GAC filtration can be successfully employed to control the abundance of high molecular NOM components, and thus the ClO(2) demand of finished water.     

Adsorption of As(V) and As(III) by nanocrystalline titanium dioxide

This study evaluated the effectiveness of nanocrystalline titanium dioxide (TiO(2)) in removing arsenate [As(V)] and arsenite [As(III)] and in photocatalytic oxidation of As(III). Batch adsorption and oxidation experiments were conducted with TiO(2) suspensions prepared in a 0.04 M NaCl solution and in a challenge water containing the competing anions phosphate, silicate, and carbonate. The removal of As(V) and As(III) reached equilibrium within 4h and the adsorption kinetics were described by a pseudo-second-order equation. The TiO(2) was effective for As(V) removal at pH<8 and showed a maximum removal for As(III) at pH of about 7.5 in the challenge water. The adsorption capacity of the TiO(2) for As(V) and As(III) was much higher than fumed TiO(2) (Degussa P25) and granular ferric oxide. More than 0.5 mmol/g of As(V) and As(III) was adsorbed by the TiO(2) at an equilibrium arsenic concentration of 0.6mM. The presence of the competing anions had a moderate effect on the adsorption capacities of the TiO(2) for As(III) and As(V) in a neutral pH range. In the presence of sunlight and dissolved oxygen, As(III) (26.7 microM or 2mg/L) was completely converted to As(V) in a 0.2g/L TiO(2) suspension through photocatalytic oxidation within 25 min. The nanocrystalline TiO(2) is an effective adsorbent for As(V) and As(III) and an efficient photocatalyst.     

Exceptional arsenic (III,V) removal performance of highly porous,nanostructured ZrO2 spheres for fixed bed reactors and the full-scale system modeling

Highly porous, nanostructured zirconium oxide spheres were fabricated from ZrO₂ nanoparticles with the assistance of agar powder to form spheres with size at millimeter level followed with a heat treatment at 450 °C to remove agar network, which provided a simple, low-cost, and safe process for the synthesis of ZrO₂ spheres. These ZrO₂ spheres had a dual-pore structure, in which interconnected macropores were beneficial for liquid transport and the mesopores could largely increase their surface area (about 98 m²/g) for effective contact with arsenic species in water. These ZrO₂ spheres demonstrated an even better arsenic removal performance on both As(III) and As(V) than ZrO₂ nanoparticles, and could be readily applied to commonly used fixed-bed adsorption reactors in the industry. A short bed adsorbent test was conducted to validate the calculated external mass transport coefficient and the pore diffusion coefficient. The performance of full-scale fixed bed systems with these ZrO₂ spheres as the adsorber was estimated by the validated pore surface diffusion modeling. With the empty bed contact time (EBCT) at 10 min and the initial arsenic concentration at 30 ppb, the number of bed volumes that could be treated by these dry ZrO₂ spheres reached ∼255,000 BVs and ∼271,000 BVs for As(III) and As(V), respectively, until the maximum contaminant level of 10 ppb was reached. These ZrO₂ spheres are non-toxic, highly stable, and resistant to acid and alkali, have a high arsenic adsorption capacity, and could be easily adapted for various arsenic removal apparatus. Thus, these ZrO₂ spheres may have a promising potential for their application in water treatment practice.     

Advanced water treatment with manganese oxide for the removal of 17alpha-ethynylestradiol (EE2)

Municipal wastewater is supposed to be one of the most important sources of endocrine-disrupting compounds (EDCs) in water. Therefore, advanced treatments and cost-efficient techniques should be developed to prevent the spread of this type of pollution into the environment. In this view, experiments were conducted in which the removal of 17alpha-ethynylestradiol (EE2), a synthetic and persistent estrogen, from water was monitored in three upstream bioreactors (UBRs), filled with, respectively, sand, granulated activated carbon (GAC) and MnO(2) granules. Tap water, spiked with 15,000ngEE2/L was filtered through the reactors with a hydraulic retention time of approximately 1h. The removal of EE2 in the sand, GAC and MnO(2) reactors was, respectively, 17.3%,>99.8% and 81.7%. The removal in the GAC reactor was mainly due to adsorption. The MnO(2) reactor, however, removed significantly more EE2 than could be predicted from its adsorption capacity, probably thanks to its catalytic properties. These catalytic properties could make it a cost-efficient technique for the removal of EE2, but further research at more environmentally relevant concentrations is needed.     

Hybrid photocatalysis/membrane treatment for surface waters containing low concentrations of natural organic matters

Since the mid-1990s, numerous studies on the treatment of drinking water by photocatalysis have been reported. Once optimised, the photocatalytic process can completely degrade numerous natural and artificial organic compounds. In this study, a hybrid photocatalysis/membrane process was used as a polishing treatment of surface water containing a small concentration of natural organic matters (i.e. total organic carbon (TOC) concentration of around 3mg/L) which may be difficult to remove using conventional filtration or coagulation. An optimum pH of 4.5 and a TiO(2) concentration of 0.1g/L were found to lead to the highest removal efficiencies. The relative effect of the individual processes featuring in the hybrid system (UV radiation, TiO(2) adsorption and membrane filtration) was also assessed for different pH values. The membrane separation process was accounted to remove around 18% of the initial TOC concentration, while TiO(2) adsorption alone was generally responsible for less than 5% of TOC removal during the 120 min of the experiments. However, when the natural water was only radiated by UV light, up to 70% of TOC was removed. A synergetic effect was observed when the three processes (TiO(2), UV and membrane) were used together. Comparison of removal efficiencies obtained during real and model (International Humic Substance Society) waters treatment by photocatalysis is also presented, revealing the importance of the nature of the feed in this type of treatment.     

Efficiency and energy requirements for the transformation of organic micropollutants by ozone, O3/H2O2 and UV/H2O2

The energy consumptions of conventional ozonation and the AOPs O₃/H₂O₂ and UV/H₂O₂ for transformation of organic micropollutants, namely atrazine (ATR), sulfamethoxazole (SMX) and N-nitrosodimethylamine (NDMA) were compared. Three lake waters and a wastewater were assessed. With p-chlorobenzoic acid (pCBA) as a hydroxyl radical (^•OH) probe compound, we experimentally determined the rate constants of organic matter of the selected waters for their reaction with ^•OH (k_OH,DOM), which varied from 2.0 × 10⁴ to 3.5 × 10⁴ L mgC⁻¹ s⁻¹. Based on these data we calculated ^•OH scavenging rates of the various water matrices, which were in the range 6.1-20 × 10⁴ s⁻¹. The varying scavenging rates influenced the required oxidant dose for the same degree of micropollutant transformation. In ozonation, for 90% pCBA transformation in the water with the lowest scavenging rate (lake Zürich water) the required O₃ dose was roughly 2.3 mg/L, and in the water with the highest scavenging rate (Dübendorf wastewater) it was 13.2 mg/L, corresponding to an energy consumption of 0.035 and 0.2 kWh/m³, respectively. The use of O₃/H₂O₂ increased the rate of micropollutant transformation and reduced bromate formation by 70%, but the H₂O₂ production increased the energy requirements by 20-25%. UV/H₂O₂ efficiently oxidized all examined micropollutants but energy requirements were substantially higher (For 90% pCBA conversion in lake Zürich water, 0.17-0.75 kWh/m³ were required, depending on the optical path length). Energy requirements between ozonation and UV/H₂O₂ were similar only in the case of NDMA, a compound that reacts slowly with ozone and ^•OH but is transformed efficiently by direct photolysis.     

Effect of fulvic acid on the sorption of Cu and Pb onto gamma-Al2O3

This work investigated the adsorption of Cu and Pb at the surface of gamma-Al(2)O(3) in the presence of fulvic acid to address the significance of dissolved organic matters on metal partitioning. Fulvic acid, obtained from International Humic Substance Society, represented dissolved organic matter. Fulvic acid concentrations employed herein were 1, 5, and 10 mg C/L, which simulated the relevant environmental conditions. Ion selective electrodes were employed to ascertain free Cu and Pb measurements. The maximum adsorption of 10mg C/L fulvic acid on gamma-Al(2)O(3) was 5 x 10(-2)mgC/mg gamma-Al(2)O(3). Fulvic acid promoted Cu adsorption in low pH conditions. The effects of fulvic acid on Pb adsorption were similar to those of Cu. The conditional stability constants of sorbed fulvic acids with Cu and Pb were determined to be in the order of 4 to 6 (log K). Cu and Pb species were modeled in heterogeneous systems using triple-layer model. Simulation results indicated that metal species are dominantly in complexation with fulvic acid, both in solution and at the gamma-Al(2)O(3) surface.     

Preparation and characterization of Pd/Al2O3 and Pd nanoparticles as standardized test material for chemical and biochemical studies of traffic related emissions

Palladium model particles similar to those emitted from catalytic car exhaust converters were prepared and characterized with the intention of providing a standardized material for investigations of the chemical behavior and bioavailability of traffic related Pd emissions. Two series of Pd particles were prepared and characterized in detail: Pd nanoparticles (2-4 nm) dispersed on aluminum oxide particles of a diameter range between 0.1 to 30 microm and "Pd-only" nanoparticles of 5-10 nm in diameter. The Pd/alpha-Al2O3 particles are very similar to particles emitted from catalytic converters by mechanical abrasion. The Pd-only particles are useful e.g. for exposure studies in which the presence of aluminum could lead to interferences when studying biological and biochemical effects. The sample preparation procedure of both series was optimized in order to achieve elemental particles with proper sizes and a narrow size distribution. The obtained particles were characterized by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selective area diffraction (SAD), laser granulometry and graphite furnace atomic absorption spectrometry (GFAAS) for the measurement of Pd concentrations.     

Degradation of Pb--EDTA complex by a H(2)O(2)/UV process

The degradation of PbEDTA in aqueous solution by a H(2)O(2)/UV process was studied. The effect of H(2)O(2) content, pH of the solution and the presence of nitrate were investigated. PbEDTA degradation by a H(2)O(2)/UV process was shown to be accompanied by simultaneous lead precipitation. PbEDTA was decomposed rapidly in acidic solutions while lead precipitation was achieved only when the pH of the solution was higher than 6. The presence of nitrate in significant amounts (0.04 M) inhibited remarkably the degradation of the complex and metal precipitation. The degradation of CdEDTA and ZnEDTA was also studied. It was found that the decomposition of metal-EDTA complex and metal removal by the H(2)O(2)/UV process depend greatly on the nature of the metal. CdEDTA and ZnEDTA were decomposed rapidly but metal precipitation was not achieved. The major by-products of the degradation of metal-EDTA complexes observed were nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), oxalic acid and nitrate.     

Magnetic powder MnO-Fe2O3 composite--a novel material for the removal of azo-dye from water

Fine powder adsorbents or catalysts often show better adsorptive or catalytic properties, but they encounter the difficulties of separation and recovery in application. In this study, four inexpensive magnetic powder MnO-Fe2O3 composites used as adsorbent-catalyst materials were prepared and characterized. These materials could be recovered efficiently by a magnetic separation method. Their adsorptive properties for the removal of an azo-dye, acid red B (ARB), from water and the regeneration of adsorbents containing ARB by catalytic combustion was studied. These powder adsorbents showed excellent adsorption towards ARB under acidic conditions. A very fast adsorption rate was observed and could be well described by a pseudo-second-order kinetics model. The adsorption capacity increased with increasing Fe content and surface area of the adsorbent, and the highest adsorption capacity of 105.3 mg/g was obtained at pH 3.5. The adsorption was not affected by the presence of Cl-, but was significantly affected by SO4(2-). The adsorbent containing ARB can be regenerated by catalytic combustion of adsorbed ARB at 400 degrees C in air. Laboratory experiments demonstrated that this material is reusable.     

Splitting tensile strength of concrete using ground granulated blast furnace slag and SiO2 nanoparticles as binder

In the present study, split tensile strength together with pore structure, thermal behavior and microstructure of concrete containing ground granulated blast furnace slag and SiO₂ nanoparticles have been investigated. Portland cement was replaced by different amounts of ground granulated blast furnace slag and the properties of concrete specimens were measured. Although it negatively impacts the properties of concrete at early ages, ground granulated blast furnace slag was found to improve the physical and mechanical properties of concrete up to 45 wt% at later ages. SiO₂ nanoparticles with the average particle size of 15 nm were partially added to concrete with the optimum content of ground granulated blast furnace slag and physical and mechanical properties of the specimens were studied. SiO₂ nanoparticle as a partial replacement of cement up to 3 wt% could accelerate C-S-H gel formation as a result of increased crystalline Ca(OH)₂ amount at the early age of hydration and hence increase split tensile strength of concrete specimens. The increased the SiO₂ nanoparticles’ content more than 3 wt% causes the reduced the split tensile strength because of the decreased crystalline Ca(OH)₂ content required for C-S-H gel formation. SiO₂ nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and few-harm pores.     

Field solar degradation of pesticides and emerging water contaminants mediated by polymer films containing titanium and iron oxide with synergistic heterogeneous photocatalytic activity at neutral pH

Photocatalytic degradation of phenol, nalidixic acid, mixture of pesticides, and another of emerging contaminants in water was mediated by TiO₂ and iron oxide immobilized on functionalized polyvinyl fluoride films (PVF^f-TiO₂-Fe oxide) in a compound parabolic collector (CPC) solar photoreactor. During degradation, little iron leaching (<0.2 mg L⁻¹) was observed. Phenol was efficiently degraded and mineralized at operational pH < 5 and nalidixic acid degradation was complete even at pH 7, but mineralization stopped at 35%. Pesticide mixture was slowly degraded (50%) after 150 min of irradiation. Degradation of the emergent contaminant mixture was successful for eight compounds and less efficient for six other compounds. The significant reactivity differences between tested compounds were assigned to the differences in structure namely that the presence of complexing or chelating groups enhanced the rates.PVF^f-TiO₂-Fe oxide photoactivity gradually increased during 20 days of experiments. X-ray photoelectron spectroscopy (XPS) measurements revealed significant changes on the catalyst surface. These analyses confirm that during photocatalysis mediated by PVF^f-TiO₂-Fe oxide, some iron leaching led to enlargement of the TiO₂ surface exposed to light, increasing its synergy with iron oxides and leading to enhanced pollutant degradation.     

Photoassisted reduction of metal ions and organic dye by titanium dioxide nanoparticles in aqueous solution under anoxic conditions

The photoassisted reduction of metal ions and organic dye by metal-deposited Degussa P25 TiO₂ nanoparticles was investigated. Copper and silver ions were selected as the target metal ions to modify the surface properties of TiO₂ and to enhance the photocatalytic activity of TiO₂ towards methylene blue (MB) degradation. X-ray powder diffraction (XRPD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were used to characterize the crystallinity, chemical species and morphology of metal-deposited TiO₂, respectively. Results showed that the particle size of metal-deposited TiO₂ was larger than that of Degussa P25 TiO₂. Based on XRPD patterns and XPS spectra, it was observed that the addition of formate promoted the photoreduction of metal ion by lowering its oxidation number, and subsequently enhancing the photodegradation efficiency and rate of MB. The pseudo-first-order rate constant (k_obs) for MB photodegradation by Degussa P25 TiO₂ was 3.94 × 10^− 2 min^− 1 and increased by 1.4-1.7 times in k_obs with metal-deposited TiO₂ for MB photodegradation compared to simple Degussa P25 TiO₂. The increase in mass loading of metal ions significantly enhanced the photodegradation efficiency of MB; the k_obs for MB degradation increased from 3.94 × 10^− 2 min^− 1 in the absence of metal ion to 4.64-7.28 × 10^− 2 min^− 1 for Ag/TiO₂ and to 5.14-7.61 × 10^− 2 min^− 1 for Cu/TiO₂. In addition, the electrons generated from TiO₂ can effectively reduce metal ions and MB simultaneously under anoxic conditions. However, metal ions and organic dye would compete for electrons from the illuminated TiO₂.     

Synergetic effect between photocatalytic degradation and adsorption processes on the removal of phenolic compounds from olive mill wastewater

The photocatalytic degradation of two phenolic compounds, p-coumaric acid and caffeic acid, was performed with a suspended mixture of TiO₂ and powdered activated carbon (PAC) (at pH = 3.4 and 8). Adsorption, direct photolysis and photocatalytic degradation were studied under different pH and UV light sources (sunlight vs. 365 nm UV lamps). The potential for reusing this catalyst mixture in sequential photocatalytic runs was examined as well. Quantum yields for the direct photolysis of caffeic acid under solar and artificial 365 nm light were calculated (for the first time) as 0.005 and 0.011, respectively.A higher removal rate of contaminants by either adsorption or photocatalysis was obtained at a low pH (pH 4). Furthermore, the addition of PAC increased the removal efficiency of the phenolic compounds. Fast removal of the pollutants from the solution over three sequential runs was achieved only when both TiO₂ and PAC were present. This suggests that at medium phenolic concentrations, the presence of PAC as a co-sorbent reduces surface poisoning of the TiO₂ catalyst and hence improves photocatalysis degradation of phenolic pollutants.The adsorption equilibrium of caffeic acid or p-coumaric acid on TiO₂, PAC and the combined mixture of TiO₂ and PAC follows the Langmuir isotherm model. Experiments with PAC TiO₂ mixture and olive mill wastewater (anaerobically treated and diluted by a factor of 10) showed higher removal of polyphenols than of chemical oxygen demand (COD). 87% removal of total polyphenols, compared to 58% of COD, was achieved after 24 h of exposure to 365 nm irradiation (7.6 W/m²) in the presence of a suspended mixture of TiO₂ and PAC, indicating “self-selectivity” of polyphenols.