Mixture Of Humic Acid Research Articles

Removal of microcystins by PAC/UF

The removal of microcystins (MC) by powdered activated carbon adsorption/ultrafiltration (PAC/UF) was investigated, focusing on PAC dose and addition mode, MC initial concentration (expressed as MC-LR eq) and on the impact of background natural organic matter (NOM), assessed through model compounds (a mixture of tannic and humic acids) and Microcystis aeruginosa culture. Constant flow experiments were performed with a hydrophilic UF hollow-fibre membrane and a mesoporous fine-powdered activated carbon. In the absence of background NOM, PAC/UF with 10 mg/L PAC and up to 20 μg/L MC-LR eq feed concentration achieved 93–98% MC removal and a cycle-averaged permeate concentration below the drinking water guideline-value adopted by the World Health Organisation (WHO) for microcystin-LR variant. Single-pulse PAC dosing in the beginning of the UF-cycle allowed slightly lower MC concentration in the permeate compared to the multi-pulse PAC addition whereas no differences were found in terms of transmembrane pressure. Hydraulic retention time of 34 and 55 min resulted in similar permeate quality. NOM type and concentration and MC initial concentration determined the PAC dose to be used. While 10 mg/L PAC effectively controlled ca. 5 μg/L MC-LR eq in a model water with 2.5 mg/L NOM or with M. aeruginosa culture (cells and algogenic organic matter) 15 mg/L PAC were unable to achieve the WHO quality with a water containing higher concentrations of NOM (5 mg/L) and microcystins ( ca. 20 μg/L MC-LR eq).

Proton Charge and Adsorption of Humic Acid and Phosphate on Goethite

Little information is available about the changes of the proton charge of goethite in the presence of phosphate (P) and humic acid (HA). The objectives of this study were to systematically measure the proton charge of the ternary mixture and adsorption of HA and P on goethite. The potentiometric titration method was used to measure proton charges in single, binary, and ternary mixtures of goethite, HA, and P as a function of pH and ionic strengths. Results showed that proton charge in the ternary mixture became more negative with increasing pH and the loadings of HA and P. The point of zero charge (PZC) decreased linearly with the initial concentrations of HA and P. At low to intermediate pH, little variation was observed in adsorption of P on goethite in the presence of HA. A small reduction in the adsorption of P in the presence of HA was observed when compared with the control (without HA loading) at high pH. In 2008, Weng et al. developed a model describing the electrostatic interaction between HA and P at the 1‐plane of the compact part of the electrical double layer (EDL). In this study, Weng et al.'s model was used to interpret the effect of adsorbed HA on the adsorption of P on goethite as well as the nonsignificant interaction of PZC between HA and P.

Formation of haloacetamides during chlorination of dissolved organic nitrogen aspartic acid

The stability of haloacetamides (HAcAms) such as dichloroacetamide (DCAcAm) and trichloroacetamide (TCAcAm) was studied under different experimental conditions. The yield of HAcAms during aspartic acid (Asp) chlorination was measured at different molar ratio of chlorine atom to nitrogen atom (Cl/N), pH and dissolved organic carbon (DOC) mainly consisted of humic acid (HA) mixture. Ascorbic acid showed a better capacity to prevent the decay of DCAcAm and TCAcAm than the other two dechlorinating agents, thiosulfate and sodium sulfite. Lower Cl/N favored the DCAcAm formation, implying that breakpoint chlorination might minimize its generation. The pH decrease could lower the concentration of DCAcAm but favored dichloroacetonitrile (DCAN) formation. DCAcAm yield was sensitive to the DOC due to higher chlorine consumption caused by HA mixture. Two possible pathways of DCAcAm formation during Asp chlorination were proposed. Asp was an important precursor of DCAN, DCAcAm and dichloroacetic acid (DCAA), and thus removal of Asp before disinfection may be a method to prevent the formation of DCAcAm, DCAN and DCAA.

Iron(III) Bioreduction in Soil in the Presence of Added Humic Substances

Despite the broad consensus that humic substances (HS) can act as electron shuttles in bioreduction processes occurring in aquatic and terrestrial environments, no published studies have presented direct evidence that electron shuttling by HS plays a role in the mechanisms of Fe(III) bioreduction in soils. We conducted experiments in which two HS with very different chemical properties, a soil humic acid and a mixture of peat humic acid with aquatic organic matter, were added to an Ultisol and incubated under anoxic conditions to evaluate their effect on Fe(III) bioreduction by the indigenous microorganisms in the soil. Our experiments were designed to have the same initial reducing capacity available from the added HS but to have very different initial total carboxyl concentrations to examine the role of Fe(II) complexation by HS in the bioreduction process. The addition of HS significantly increased soluble Fe(II) production relative to that observed in control experiments without added HS. Moreover, after an initial period of incubation, soluble Fe(II) production was accelerated by the presence of a higher initial carboxyl content. These trends support the hypothesis that, at the initial stages of in Fe(III) bioreduction, electron shuttling dominates, whereas later Fe(II) complexation dominates. Our results apparently are the first to demonstrate directly that added HS can indeed enhance the bioreduction of Fe(III) minerals in soil by at least two different mechanisms.

Application of asymmetric flow field-flow fractionation (AsFlFFF) coupled to inductively coupled plasma mass spectrometry (ICPMS) to the quantitative characterization of natural colloids and synthetic nanoparticles

A straightforward quantification method is presented for the application of asymmetric flow field-flow fractionation (AsFlFFF) combined with inductively coupled plasma mass spectrometry (ICPMS) to the characterization of colloid-borne metal ions and nanoparticles. Reproducibility of the size calibration and recovery of elements are examined. Channel flow fluctuations are observed notably after initiation of the fractionation procedure. Their impact on quantification is considered by using (103)Rh as internal reference. Intensity ratios measured for various elements and Rh are calculated for each data point. These ratios turned out to be independent of the metal concentration and total sample solution flow introduced into the nebulizer within a range of 0.4-1.2 mL min(-1). The method is applied to study the interaction of Eu, U(VI) and Th with a mixture of humic acid and clay colloids and to the characterization of synthetic nanoparticles, namely CdSe/ZnS-MAA (mercaptoacetic acid) core/shell-coated quantum dots (QDs). Information is given not only on inorganic element composition but also on the effective hydrodynamic size under relevant conditions. Detection limits (DLs) are estimated for Ca, Al, Fe, the lanthanide Ce and the natural actinides Th and U in colloid-containing groundwater. For standard crossflow nebulizer, estimated values are 7 x 10(3), 20, 3 x 10(2), 0.1, 0.1 and 7 x 10(-2) microg L(-1), respectively. DLs for Zn and Cd in QD characterization are 28 and 11 microg L(-1), respectively.

Assessing nanofiltration fouling in drinking water treatment using fluorescence fingerprinting and LC-OCD analyses

The natural organic matter (NOM) components causing fouling of nanofiltration membranes used in drinking water applications consists in a complex mixture of humic and fulvic acids, proteins, and carbohydrates of various molecular size and functional groups. Understanding the characteristics of NOM fractions such as humic substances (HS) and biopolymers (proteins and polysaccharides) as foulants is of paramount importance to develop fouling control strategies. Fluorescence spectroscopy is becoming an increasingly popular method for characterizing NOM and shows good potential for online monitoring, as minimal sample pre-treatment and preparation is required, high instrumental sensitivity is available and the technique is non-destructive in nature. In this research an innovative approach involving both fluorescence and LC-OCD analyses is used to identify and to characterise organic membrane foulant.

Breakage and re-growth of flocs formed by alum and PACl

The efficiency of coagulation and flocculation can be significantly improved through flocs breakage and re-growth under appropriate conditions. Investigation was carried out to examine the formation, breakage and re-growth of flocs formed by kaolin or the mixture of kaolin and humic acid with aluminum sulfate (‘alum’) or polyaluminum chloride (‘PACl’). The reversibility and mechanism in the process of flocs breakage and re-growth were explored through conventional jar test procedure and continuous optical monitoring (PDA). There was full re-growth of flocs in kaolin water coagulated in charge neutrality (alum or PACl), which indicated a significant reversibility of flocs break-up process; the process displayed a distinct irreversibility in sweep flocculation. The addition of humic acid weakened the reversibility, and alum showed better shear resistance than PACl. The residual turbidity after breakage and re-growth was lower than before breakage when charge neutrality dominates the coagulate mechanism, but the result was reverse in sweep flocculation.

Nuclear magnetic resonance relaxometry as a spectroscopic probe of the coordination sphere of a paramagnetic metal bound to a humic acid mixture

Protons on water molecules are strongly affected by paramagnetic ions. Since the acid–base properties of water facilitate rapid proton exchange, a single proton nuclear magnetic resonance (NMR) signal is seen in aqueous solutions of paramagnetic ions. Proton relaxation times are significantly affected by paramagnetic species and the readily detectable single signal serves as a powerful amplifier of the information contained concerning the protons in the paramagnetic environment. Where water molecules coordinated to free paramagnetic ions and to metal complexes of ligands that form non-labile (on the NMR time scale) complexes, the effects on water in the two environments can be distinguished. This can provide information on the nature of the ligand binding sites. The example of Cu 2+ bound to the Laurentian humic acid mixture reported here using convenient low field NMR relaxometers shows that the information can enrich our understanding of complexation and speciation in the presence of complex mixture ligands characteristic of natural water systems. In this case, the data underline the role of aggregation and conformation in defining the complexation sites.

Hygroscopic growth and water uptake kinetics of two-phase aerosol particles consisting of ammonium sulfate, adipic and humic acid mixtures

The hygroscopic growth of solid aerosol particles consisting of mixtures of ammonium sulfate and either adipic acid or Aldrich humic acid sodium salt was characterized with a hygroscopicity tandem differential mobility analyzer and an electrodynamic balance. In particular, the time required for the aerosol particle phase and the surrounding water vapor to reach equilibrium at high relative humidity (RH) was investigated. Depending on the chemical composition of the particles, residence times of > 40 s were required to reach equilibrium at 85% RH, yielding up to a 7% reduction in the measured hygroscopic growth factors from measurements at 4 s residence time compared to measurements at equilibrium. We suggest that the solid organic compound, when present as the dominant component, encloses the water-soluble inorganic salt in veins and cavities, resulting in the observed slow water uptake. Comparison with predictions from the Zdanovskii–Stokes–Robinson relation shows enhanced water uptake of the mixed particles. This is explained with the presence of the salt solution in veins resulting in a negative curvature of the solution meniscus at the opening of the vein. In conclusion, it is important for studies of mixtures of water soluble compounds with insoluble material to allow for sufficient residence time at the specified humidity to reach equilibrium before the hygroscopicity measurements.

Variability Associated with Suppression of Gray Mold (Botrytis cinerea) on Geranium by Foliar Applications of Nonaerated and Aerated Compost Teas.

The use of compost teas in agriculture and urban landscapes is increasing, but there is conflicting information on which methods are suitable for obtaining compost teas that suppress disease when applied to plants. Numerous compost tea production parameters (compost source, aeration, nutrient additives, production duration, and use of application adjuvants) were tested for suppressing gray mold (Botrytis cinerea) on geranium. While individual compost tea batches did significantly reduce disease, the majority of compost teas did not significantly suppress gray mold of geranium. For nonaerated compost tea (NCT), the most consistent, significant disease suppression was associated with particular compost samples and increased production time, with little effect of periodic stirring or the addition of nutrients at the onset of production. Continuously aerating compost tea did not significantly increase disease suppression compared with nonaerated compost teas. Preparing aerated compost tea (ACT) with nutrient additives did not consistently increase disease suppression; however, 67% of ACT batches made with a mixture of kelp extract, rock dust, and humic acid significantly reduced disease. Applying ACT with spray adjuvants significantly reduced disease compared with ACT with no adjuvants. The variability in gray mold suppression from NCT and ACT applications indicates that disease control would not be commercially acceptable unless there are no other alternatives due to production constraints, e.g., organic standards.

Application of an ozonation–adsorption–ultrafiltration system for surface water treatment

Abstract Investigations are presented on the effect of the preliminary ozonation on ultrafiltration (UF) and powdered activated carbon (PAC) /UF process performance, especially on permeate flux decline and the effectiveness of model organics removal. Flat membranes from regenerated cellulose were used. A model solution was prepared as a mixture of humic acids and phenol. PAC dosage was equal to 100 mg/l−1. The ozone dosages were in the range of 1–3 mg O3 l−1 (0.2–0.6 mg O3/mg TOC). It was found that the most advantageous configuration was preliminary ozonation with an ozone dosage of 0.4 mgO3/mg TOC–UF. The permeate flux reached a value equal to the pure water flux value. Moreover, a very high effectiveness of model organics removal was obtained: TOC was reduced by about 96% and UV254 absorbance was removed completely. When PAC was added to the feed containing humic acids without ozonation, a drop in a permeate flux was observed compared to UF. Similarly, the addition of PAC to feed treated with ozone resulted in a significant drop in the permeate flux in comparison with pure water flux, regardless of ozone dosage applied.

Humic acid preparation, properties and interactions with metals lead and cadmium

Humic acid (HA) extracted from soil is investigated in terms of its cation exchange capacity (CEC), zero point of charge (zpc), oxygen containing functional group content, scanning electron microscope (SEM) images, and pH. The CEC of HA that was dried was approximately half the CEC of hydrated HA. Metal retention by HA was studied by conducting 24 h batch equilibrium tests with lead (Pb, as PbCl 2) and cadmium (Cd, as CdCl 2) and HA at pH 4 and 6, and with a mixture of HA, mackinawite and kaolinite. The reactivity of the HA towards Pb and Cd was reduced when it was combined with the mackinawite and kaolinite. The mackinawite raised the pH and dissolved some of the HA, until sufficient reactions between the metals and mixture lowered the pH enough for the dissolved HA to solidify and remove more metal from solution. HA bonding with the mackinawite and kaolinite reduced the HA sites available for metal uptake. The functional group content of the HA provided indications regarding the origin of the HA, the extent of humification and the presence of less decomposed fractions. The CEC of the HA could conservatively predict the amount of metal uptake. Low pH conditions are favorable for metal removal from solution by HA because the zpc of the HA was below pH 0.5 and because at higher pHs HA begins to dissolve. HA, especially in the hydrated phase, may represent an important material for metal removal from waters and wastewaters containing metals.

Use of equilibrium and initial metal concentrations in determining Freundlich isotherms for soils and sediments

Batch equilibrium test results of Pb and Cd retention by kaolinite, humic acid and mackinawite and mixtures of these soil/sediment materials are modeled using Freundlich isotherms with the retained metal plotted as a function of the equilibrium metal concentration, C e and as a function of the initial metal concentration, C i. When C i rather than C e is used, smaller values of K F and larger values of 1 / n are obtained and this means the isotherm is more linear. There is no significant difference in goodness of fit for the two types of isotherms based on the coefficient of determination, r 2 and a normalized deviation, Δ q. Advantages in using C i are that no data points need to be excluded when metal is completely retained by the adsorbent and it is easier to compare the same range of metal concentrations on one graph. A unified sorption variable K u is evaluated for each isotherm. Since K u represents the changing slope of the Freundlich isotherm, the value of C i or C e needs to be specified with the value of K u. A dimensionless form of K u was developed so as to permit more universal application of this parameter and K u could potentially be used in transport prediction models. r 2 and Δ q together were better able to quantify goodness of fit of the data with the Freundlich isotherm than either of the two parameters separately.

COMPARISON OF GLOMALIN AND HUMIC ACID IN EIGHT NATIVE U.S. SOILS

Two important extractable fractions of soil organic matter (SOM) arehumic acid (HA) and glomalin-related soil protein (glomalin). Optimizing the purity of each fraction is necessary to correlate fraction quantity and molecular characteristics with soil quality. Manipulation of extraction sequence and controlled precipitation of HA were used to evaluate co-extraction of HA and glomalin. Eight bulk soil samples (0 to 10 cm depth) were collected from four U.S. states (Colorado, Nebraska, Maryland, and Georgia). In Experiment 1, glomalin extraction (50 mM citrate, pH 8.0, at 121 °C) was followed by HA extraction (0.1 N NaOH at room temperature), and Experiment 2 used the reciprocal sequence. Experiment 2 HA was precipitated stepwise at pH levels 2.5, 2.0, and 1.0. Gravimetric weight, Bradford-reactive soil protein (BRSP), and immunoreactive soil protein (IRSP), along with percentages of C, N, H, and Fe, were used to compare glomalin and HA. The HA fraction from Experiment 2 contained 2-fold greater amounts of BRSP than HA from Experiment 1 and showed that pre-extraction of glomalin improved the purity of HA. The glomalin fraction from Experiment 1 contained 1.5 times the BRSP of glomalin from Experiment 2 and was twice the gravimetric weight. BRSP and gravimetric weight were concentrated in HA that precipitated at pH 2.5 or 2.0 and percentage IRSP was significantly higher in the pH 2.5 precipitate. The results indicate that glomalin should be extracted first and examined as a biomolecule separate from the humic acid mixture. Percentages C, H, N, and Fe in glomalin varied across soils and experiments. In seven soils, the changes inFe percentage in glomalin from Experiment 1 to 2 were significantly correlated with the changes in glomalin weight and %C. Iron in glomalin from Experiment 1 was related to soil pH and clay content, whereas soil organic C was positively and significantly correlated with Experiment 1 glomalin BRSP and IRSP. In Experiment 1, a recalcitrant pool of glomalin was released by treating soil with NaOH, suggesting that a fraction of glomalin is difficult to remove from soil and glomalin extraction efficiency could be improved. Refinements to extraction and purification protocols such as pretreatment of soils with HCl and sequential extraction can facilitate studies on organic matter structure and function.

Triplet states of humic acids studied by laser flash photolysis using different excitation wavelengths

The spectra and kinetics of short-lived intermediates formed from aqueous (0.1 N NaOH) solutions of the natural mixture of humic and fulvic acids (HFA) were studied by laser flash photolysis using excitation wavelengths of 337, 390, 470, and 520 nm. Laser photolysis of HFA with light of 520 and 470 nm results in the formation of triplet excited states (THFA) characterized by the broad absorption spectrum with a maximum near 630 nm and lifetimes of ∼0.15 ms in deoxygenated solutions. The formation of two types of THFA with lifetimes of ∼0.1 and 2 ms and absorption spectra with maxima at 570 nm is observed under photolysis with light of 337 and 390 nm. The estimation of quantum yields of THFA gives ∼1 and 0.3% under photolysis with excitation wavelengths of 337 and 520 nm, respectively. The rate constants of THFA quenching by molecular oxygen are equal to (7—8)·108 L mol–1 s–1.

Molecular weight characteristics of humic substances from different environments as determined by size exclusion chromatography and their statistical evaluation.

Recorded molecular weights (MWs) for humic substances (HS) range from a few hundred to millions of daltons. For purposes of defining HS as a specific class of chemical compounds, it is of particular importance to ascertain if this broad range of MWs can be attributed to actual variability in molecular properties or is simply an artifact of the analytical techniques used to characterize HS. The main objectives of this study were (1)to establish if a preferential range of MWs exists for HS and (2) to determine any consistent MW properties of HS. To reach the goal, we have undertaken an approach to measure under standardized conditions the MW characteristics of a large set of HS from different natural environments. Seventy-seven humic materials were isolated from freshwater, soil, peat, and coal, such that each possessed a different fractional composition: humic acid (HA), fulvic acid (FA), and a nonfractionated mixture of HA and FA (HF). Size exclusion chromatography (SEC) was used as the analytical technique to determine molecular weight characteristics. The MW distributions were characterized by number (Mn) and weight (Mw) average MW, and by polydispersity. The complete range of Mw values varied within 4.7-30.4 kDa. The maximum Mw values were observed for peat HF and soil HA, whereas the smallest weights were measured for river water HF. Maximum values of polydispersity (3.5-4.4) were seen for peat HF and soil HA, while much lower values (1.6-3.1) were found for all preparations isolated with XAD-resins. Statistical evaluation showed consistent Mw and Mn variations with the HS source, while polydispersity was mostly a function of the isolation procedure used. A conclusion was made that HS have a preferential range of MW values that could characterize them as a specific class of chemical compounds.

Ionization and fragmentation of humic substances in electrospray ionization Fourier transform-ion cyclotron resonance mass spectrometry.

Electrospray ionization (ESI) was combined with ultra-high-resolution Fourier transform-ion cyclotron resonance mass spectrometry (FTICR MS) to characterize complex humic and fulvic acid mixtures. Lower than expected molecular weight distributions previously observed for humics when analyzed by ESI-MS have fueled speculation about a bias in favor of low molecular weight. Multiply charged ions, ionization suppression, and sample fragmentation have all been suggested as sources of this low molecular weight bias. In this work, resolution of the individual components of humic mixtures within a 1 mass-to-charge unit window was accomplished by FTICR MS at 9.4 T. At mass resolving powers between 60,000 (high mass) and 120,000 (low mass), it was possible to determine that virtually all ions present in spectra of Suwannee River fulvic and humic acid are singly charged, thus eliminating inadequate accounting for multiply charged ions as a primary source of any low molecular weight bias. The high-resolution mass spectra also revealed the presence of molecular families containing ions that differ from each other in degree of saturation, functional group substitution (primarily CH vs N and CH4 vs O), and number of CH2 groups. Ionization suppression and ion fragmentation were addressed for humic and fulvic acid mixtures and well-characterized poly(ethylene glycol) (PEG) mixtures with average molecular weights of 8000 and 10,000. Although these high molecular weight PEG mixtures fragment extensively under traditional positive-ion mode ESI conditions, similar fragmentation could not be confirmed for humic and fulvic acid mixtures.

Influence of herbicide structure, clay acidity, and humic acid coating on acetanilide herbicide adsorption on homoionic clays.

Adsorption of chloroacetanilide herbicides on homoionic montmorillonite was studied by coupling batch equilibration and FT-IR analysis. Adsorption decreased in the order metolachlor > acetochlor > alachlor > propachlor on Ca(2+)- or Mg(2+)-saturated clays and in the order metolachlor > alachlor > acetachlor > propachlor on Al(3+)- or Fe(3+)-saturated clays. FT-IR spectra showed that the carbonyl group of the herbicide molecule was involved in bonding. For the same herbicide, adsorption of alachlor, acetachlor, and metolachlor on clay followed the order Ca(2+) approximately Mg(2+) < Al(3+) < or = Fe(3+), which coincided with the increasing acidity of homoionic clays. Adsorption of propachlor, however, showed an opposite dependence, suggesting a different governing interaction. In clay and humic acid mixtures, herbicide adsorption was less than that expected from independent additive adsorption by the individual constituents, and the deviation was dependent on the clay-to-humic acid ratio, with the greatest deviation consistently occurring at a 60:40 clay-to-humic acid ratio.

Leachability of Cu and Ni in wood ash-amended soil as impacted by humic and fulvic acid

Land application is a cost-effective way of disposing of wood ash. However, high volume wood ash application tends to increase soil pH, solubilizing soil organic matter (SOM), and enhancing metal mobility. Column studies (1.5×20 cm) were conducted to determine the leachability of Cu and Ni in an ash-amended soil. In the first study, deionized water was used to leach three columns: ash, ash mixed with topsoil, and ash mixed with topsoil overlying a spodic horizon. In the second study, humic acid (HA), fulvic acid (FA), and a mixture of humic and fulvic acids (HAFA) were used to leach ash columns. Leaching was conducted, one pore volume (PV) at a time, under unsaturated conditions. Leachate concentrations of dissolved organic carbon (DOC), Cl, Cu, and Ni, as well as pH were determined. Leachate pH ranged from ∼10 to ∼11 in the water- and acid-leached columns, respectively. In the ash-only columns, Cu leaching was in the form of soluble complexes with Cl. When wood ash was mixed with soil, Cu leached as soluble complexes with DOC at high pH (∼10). Columns with a Bh horizon had 30% less leaching of Cu, possibly due to increased metal retention. Nickel leachability was not affected to the same extent as Cu. Organic acid-leached ash columns showed lower DOC, Cu, and Ni leaching, suggesting that these two metals and DOC were precipitating out with DOC at the high ionic strengths of these solutions (>0.3 mol dm −3). Precipitation was greater in the more reactive FA-leached columns. This study shows the need to understand the system to which wood ash is applied to minimize potential harmful effects.

Removal of organic matter from water by PAC/UF system

The laboratory-scale ultrafiltration (UF) experiments were conducted to determine the effect of the presence of powdered activated carbon (PAC) on the UF process performance, in terms of flux decline and the possibilities of membranes cleaning during backwashing. Poly(vinylidene fluoride) membranes formed by the phase inversion technique were used in the UF experiments. A model solution was prepared as a mixture of humic acids (HA) and phenol in concentration of 10 and 1 mg l −1, respectively. Commercial powdered activated carbons CWZ 11 and CWZ 30 (Gryfskand Sp. z o. o., Hajnówka, Poland) were used as the adsorbents. PAC dosage was in the range of 10–100 mg PAC l −1. The process was carried out in the cross-flow system. It was found that PAC addition to the distilled water leads to a small drop in the permeate flux, regardless of PAC dose and its type. Although PAC particles are too large to block the membrane pores inside, they deposit on the membrane surface and partially can plug the surface pores. The experimental results demonstrate that the backwashing process applied in combined PAC/UF system was especially effective when PAC dosages were <20 mg PAC l −1. However, a similar permeate flux was maintained for all carbon dosages used and reached the value of about 1 m 3 m −2 d −1. Moreover, no further drop in the permeate flux for PAC addition to the solution containing foulants (HA) was observed. Effectiveness of the removal of HA and phenol from the model solutions was also investigated. In the PAC/UF system HA were removed in about 90%, whereas the complete removal of phenol was achieved for PAC dosage equal to 100 mg l −1.