Biochar as Alternative Material for Heavy Metal Adsorption from Groundwaters: Lab-Scale (Column) Experiment Review.

The purpose of this manuscript is to present a review of laboratory experiments (including methodology and results) that use biochar, a specific carbon obtained by a pyrolysis process from different feedstocks, as an alternative material for heavy metal adsorption from groundwater. In recent years, many studies have been conducted regarding the application of innovative materials to water decontamination to develop a more sustainable approach to remediation processes. The use of biochar for groundwater remediation has particularly attracted the interest of researchers because it permits the reuse of materials that would be otherwise disposed of, in accordance with circular economy, and reduces the generation of greenhouse gases if compared to the use of virgin materials. A review of the different approaches and results reported in the current literature could be useful because when applying remediation technologies at the field scale, a preliminary phase in which the suitability of the adsorbent is evaluated at the lab scale is often necessary. This paper is therefore organised with a short description of the involved metals and of the biochar production and composition. A comprehensive analysis of the current knowledge related to the use of biochar in groundwater remediation at the laboratory scale to obtain the characteristic parameters of the process that are necessary for the upscaling of the technology at the field scale is also presented. An overview of the results achieved using different experimental conditions, such as the chemical properties and dosage of biochar as well as heavy metal concentrations with their different values of pH, is reported. At the end, numerical studies useful for the interpretation of the experiment results are introduced.

A sustainable approach to enhance heavy hydrocarbons removal in landfarming treatment.

The present study aimed to evaluate the best strategy to enhance the degradation rate of heavy petroleum hydrocarbons (HPH) contaminated soil in a landfarming plant. Samples of real contaminated soil, further spiked with HPH, were treated in mesocosm reactors simulating the landfarming system. One reactor was operated without any modification compared to the real landfarming plant. The other three reactors were operated with different strategies to improve the removal rate: biostimulation (BS) through the addition of nitrogen and phosphorus; bioaugmentation (BA) with the inoculation of sludge produced in the treatment of the process water from the oil re-fining plant of the same industrial area; combination of biostimulation and bioaugmentation (BAS). The biostimulation (BS) was the most effective strategy, leading to a reduction of the remediation time by 35% as compared to the traditional treatment. Bioaugmentation (BA) also provided positive effects leading to a reduction of the remediation time by 24%; its performance improved further when the addition of sludge was combined with the increase of phosphorous (BAS). Therefore, the key tool was represented by the phosphorous availability, whereas the application of sludge was most useful to provide waste with a new possibility of reuse, thus fulfilling the principles of the circular economy. The final characterization showed that the treated soil was suitable for reuse in industrial areas according to the legislation in force.

A step forward on site-specific environmental risk assessment and insight into the main influencing factors of CECs removal from wastewater.

The presence of Contaminants of Emerging Concern (CECs) in water systems has been recognized as a potential source of risk for human health and the ecosystem. The present paper aims at evaluating the effects of different characteristics of full-scale Wastewater Treatment Plants (WWTPs) on the removal of 14 selected CECs belonging to the classes of caffeine, illicit drugs and pharmaceuticals. Particularly, the investigated plants differed because of the treatment lay-out, the type of biological process, the value of the operating parameters, the fate of the treated effluent (i.e. release into surface water or reuse), and the treatment capacity. The activity consisted of measuring concentrations of the selected CECs and also traditional water quality parameters (i.e. COD, phosphorous, nitrogen species and TSS) in the influent and effluent of 8 plants. The study highlights that biodegradable CECs (cocaine, methamphetamine, amphetamine, benzoylecgonine, 11-nor-9carboxy-Δ9-THC, lincomycin, trimethoprim, sulfamethoxazole, sulfadiazine, sulfadimethoxine, carbamazepine, ketoprofen, warfarin and caffeine) were well removed by all the WWTPs, with the best performance achieved by the MBR for antibiotics. Carbamazepine was removed at the lowest extent by all the WWTPs. The environmental risk assessed by using the site-specific value of the dilution factor resulted to be high in 3 out of 8 WWTPs for carbamazepine and less frequently for caffeine. However, the risk was reduced when the dilution factor was assumed equal to the default value of 10 as proposed by EU guidelines. Therefore, a specific determination of this factor is needed taking into account the hydraulic characteristics of the receiving water body.

Physical-Chemical Characterization of Different Carbon-Based Sorbents for Environmental Applications.

Biochar has been used in various applications, e.g., as a soil conditioner and in remediation of contaminated water, wastewater, and gaseous emissions. In the latter application, biochar was shown to be a suitable alternative to activated carbon, providing high treatment efficiency. Since biochar is a by-product of waste pyrolysis, its use allows for compliance with circular economics. Thus, this research aims to obtain a detailed characterization of three carbonaceous materials: an activated carbon (CARBOSORB NC 1240®) and two biochars (RE-CHAR® and AMBIOTON®). In particular, the objective of this work is to compare the properties of three carbonaceous materials to evaluate whether the application of the two biochars is the same as that of activated carbon. The characterization included, among others, particle size distribution, elemental analysis, pH, scanning electron microscope, pore volume, specific surface area, and ionic exchange capacity. The results showed that CARBOSORB NC 1240® presented a higher specific surface (1126.64 m2/g) than AMBIOTON® (256.23 m2/g) and RE-CHAR® (280.25 m2/g). Both biochar and activated carbon belong to the category of mesoporous media, showing a pore size between 2 and 50 nm (20-500 Å). Moreover, the chemical composition analysis shows similar C, H, and N composition in the three carbonaceous materials while a higher O composition in RE-CHAR® (9.9%) than in CARBOSORB NC 1240 ® (2.67%) and AMBIOTON® (1.10%). Differences in physical and chemical properties are determined by the feedstock and pyrolysis or gasification temperature. The results obtained allowed to compare the selected materials among each other and with other carbonaceous adsorbents.

Valorisation of residues from municipal wastewater sieving through anaerobic (co-)digestion with biological sludge.

The Circular and Green Economy principles is inspiring new approaches to municipal wastewater treatment plants (MWWTPs) design and operation. Recently, an ever-growing interest is devoted to exploring the alternatives for switching the WWTPs from being able to 'simply' removing contaminants from water to biorefinery-like plants where energy and material can be recovered. In this perspective, both wastewater and residues from process can be valorised for recovering nutrients (N and P), producing value added products (i.e. biopolymers), energy vectors and biofuels (i.e. bio-H2, bio-CH4 and bioethanol). As an additional benefit, changing the approach for WWTPs design and operation will decrease the overall amount of landfilled residues. In this context, the present research is aimed at evaluating the CH4 production potential of MWW screening units' residues. While such a stream is typically landfilled, the expected progressive increase of biodegradable matter content due to the ban on single-use plastic along with the boost of bioplastics makes the investigation of different biochemical valorisation routes more and more interesting from an environmental and economical perspective. Thus, a full-scale data collection campaign was performed to gain information on screening residues amount and properties and to analyse the relationship with influent flowrate. The most relevant residue properties were measured, and lab-scale tests were carried out to evaluate the bio-CH4 potential.

Impact of COVID19 restrictions on organic micropollutants in wastewater treatment plants and human consumption rates.

COVID19 pandemic and the consequent restrictions to constrain SARS-CoV-2 spreading produced several impacts on the worldwide population. The present study focused on 10 Organic Micropollutants (illicit drugs, pharmaceuticals including some antibiotics and caffeine) and aimed to assess: (1) if COVID19 pandemic restrictions affected the load of those contaminants released into the sewage network and consequently the removal achieved by the Wastewater Treatment Plants; (2) if pursuant to the COVID19 pandemic, there was a change in population consumption rates of the same compounds through the wastewater-based epidemiology (WBE) approach. Two full-scale wastewater treatment plants (WWTPs) located in Central Italy were chosen as case studies, which are distinguished by different characteristics of the catchment area and water treatment layouts. The study was based on a 2-years monitoring activity of the concentration of the above organic micropollutants, traditional water quality parameters (COD, TSS, nitrogen compounds, total phosphorous) and flow rate in the influent and effluent. The statistical analysis of the monitoring data showed an increase of the influent load of most of the organic micropollutants. A decrease from 22% to -18% of the median removal efficiency was observed for carbamazepine in the WWTP with the lower treatment capacity only. The other compounds were removed roughly at the same rate. The application of the WBE approach demonstrated an increase in the consumption rate of cocaine, trimethoprim, sulfamethoxazole, sulfadiazine, carbamazepine and above all caffeine during the COVID19 restrictions period. These results highlight that COVID19 pandemic affected people's lifestyle and habits also as far as drugs consumption is concerned, which in turn might have an impact on the treatment efficacy of plants and finally on the receiving water body quality. Therefore, it is mandatory to keep monitoring to improve knowledge and eventually to implement the required measures to address this new problem.

Effect of ultrasonic post-treatment on anaerobic digestion of lignocellulosic waste.

This paper evaluates the effects of ultrasonication (US) applied, individually or in combination with a mechanical treatment, to the effluent of anaerobic digestion (AD) of lignocellulosic waste, on methane (CH4) production. US of the substrate downstream of AD is a relatively novel concept aimed at improving the degradation of recalcitrant components in order to enhance the overall energy efficiency of the process. US tests were carried out on real digestate samples at different energies (500-50,000 kJ/kg total solids (TS), corresponding to sonication densities of 0.08-0.45 W/ml). AD tests were performed on mixtures of sonicated (Sus) and untreated (S) substrate at two different Sus: S ratios (25:75 and 75:25 w/w), simulating post-sonicated material recycling to the biological process. The US effect was estimated through the solubilization degree of organic matter, as well as the CH4 production yield and kinetics, which were all found to be enhanced by the treatment. At Sus: S = 75:25 and Es ≥ 20,000 kJ/kg TS (0.25 W/ml), CH4 production improved by 20% and the values of the kinetic parameters increased by 64-82%.

The Sensitivity of a Specific Denitrification Rate under the Dissolved Oxygen Pressure.

The biological denitrification process is extensively discussed in scientific literature. The process requires anoxic conditions, but the influence of residual dissolved oxygen (DO) on the efficiency is not yet adequately documented. The present research aims to fill this gap by highlighting the effects of DO on the specific denitrification rate (SDNR) and consequently on the efficiency of the process. SDNR at a temperature of 20 °C (SDNR20°C) is the parameter normally used for the sizing of the denitrification reactor in biological-activated sludge processes. A sensitivity analysis of SNDR20°C to DO variations is developed. For this purpose, two of the main empirical models illustrated in the scientific literature are taken into consideration, with the addition of a deterministic third model proposed by the authors and validated by recent experimentations on several full-scale plants. In the first two models, SDNR20°C is expressed as a function of the only variable food:microrganism ratio in denitrification (F:MDEN), while in the third one, the dependence on DO is made explicit. The sensitivity analysis highlights all the significant dependence of SDNR20°C on DO characterized by a logarithmic decrease with a very pronounced gradient in correspondence with low DO concentrations. Moreover, the analysis demonstrates the relatively small influence of F:MDEN on the SDNR20°C and on the correlation between SDNR20°C and DO. The results confirm the great importance of minimizing DO and limiting, as much as possible, the transport of oxygen in the denitrification reactor through the incoming flows and mainly the mixed liquor recycle. Solutions to achieve this result in full-scale plants are reported.

Effects of low-dosage ozone pre-treatment on the anaerobic digestion of secondary and mixed sludge.

The present study investigated the effects of ozonation pre-treatment at low-ozone dosage (below 100 mgO3/gTS0) with respect to previous studies, on the anaerobic digestion of waste-activated sludge alone and a mixture of activated sludge and primary sludge. Methane production and volatile suspended solids reduction efficiency were determined for different specific ozone dosages and compared with the values obtained in the absence of pre-treatment. Among the dosages tested in the study (from 4.8 to 73.2 mgO3/gTS0 for mixed sludge and from 3.5 to 53.6 mgO3/gTS0 for waste-activated sludge), the best results were obtained at the lowest ones: 4.8 and 3.5 mgO3/gTS0 for mixed sludge and waste-activated sludge, respectively. Indeed, at this dosage, an additional methane production of about 6% and 30% was achieved for mixed and waste-activated sludge, respectively; furthermore, the maximum CH4 production rate increased of about 21% and 33% for mixed and waste-activated sludge, respectively. With respect to the Gompertz model, the modified logistic model provided the best agreement to the experimental data of the specific methane yield production. The present study demonstrated the importance of investigating the application of low dosages when ozonation is being evaluated as a pre-treatment to enhance anaerobic digestion performance.

Experimental and numerical evaluation of Groundwater Circulation Wells as a remediation technology for persistent, low permeability contaminant source zones.

Contaminants removal stoked inside low permeability zones of aquifers is one of the most important challenge of groundwater remediation process today. Low permeability layers can be considered persistent secondary sources of contamination because they release pollutants by molecular diffusion after primary source of contamination is reduced, causing long plum tails (Back-Diffusion). In this study, the Groundwater Circulation Well (GCW) system was investigated as an alternative remediation technology to the low efficient traditional pumping technologies to restore contaminated low permeability layers of aquifers. The GCW system creates vertical groundwater circulation cells by drawing groundwater through a screen of a multi-screen well and discharging it through another screen. The suitability of this technology to remediate contaminated low permeability zones was investigated by laboratory test and numerical simulations. The collected data were used to calibrate a model created to simulate the Back-Diffusion process and to evaluate the effect of different pumping technologies on the depletion time of that process. Results show that the efficiency of the GCW is dependent on the position and on the geometry of the low permeability zones, however the GCW system appears more suitable to restore contaminated low permeability layers of aquifers than the traditional pumping technology.

A laboratory-study on the analytical determination and removal processes of THC-COOH and bezoylecgonine in the activated sludge reactor.

The present study focused on 11-nor-9carboxy-Δ9-THC (THC-COOH) and Benzoylecgonine (BE), the most common metabolites of cannabis and cocaine, respectively, present in the domestic sewage entering the wastewater treatment plants. The aims of the study were: (1) to validate the analytical method of detection in wastewater and sludge; (2) to determine contribution of biodegradation and other processes to the removal in the biological reactor of the wastewater treatment plant (WWTP) and the response of biomass to different drug concentrations. The Ultra-Performance Liquid Chromatography coupled to tandem Mass Spectrometry method showed to be repeatable and reliable (recovery>75%; repeatability<10-15%; bias uncertainty<10) for measurements in wastewater; the ultrasound assisted extraction (USE) demonstrated to be reliable as pre-treatment of activated sludge solid phase. Both drugs were fully removed from the liquid phase in the lab-scale biological reactor within 24 h. Biodegradation was the main BE removal mechanism, and the first order kinetic model provided the best fitting of the experimental data. THC-COOH was mainly removed due to a combination of adsorption and biodegradation; adsorption was better described by the pseudo-second order kinetic model and the Freundlich isotherm. Both drugs at the higher concentrations caused inhibition of nitrogen oxidation and carbon removal.

Fate of selected drugs in the wastewater treatment plants (WWTPs) for domestic sewage.

The wide diffusion of Emerging Organic Micropollutants (EOMs) in the environment is receiving increasing attention due to their potential toxicological effects on living organisms. So far, the Wastewater Treatment Plants (WWTPs) have not been designed with the purpose to remove these contaminants; therefore, they can represent the major source of release into the environment both through the effluent and the wasted sludge. The fate of EOMs in the WWTPs is still not completely known; further investigations are therefore needed to assess if it is possible to exploit the existing treatment units to reduce EOM concentrations or which processes must be implemented to this purpose. Among the wide class of EOMs, the present study focused on the following drugs of abuse: amphetamine (AM), methamphetamine (MET), 11-nor-Δ9-THC-9carboxy (THC-COOH) and benzoylecgonine (BEG). Presence and removal efficiency of these drugs in the activated sludge tank of a WWTP for domestic sewage was investigated through analyses at both full-scale and laboratory scale. Determinations conducted in the full-scale WWTP highlighted that, among the searched drugs, AM was found to be the most abundant in the influent and effluent of the biological oxidation tank, while 11-nor-Δ9-THC-9carboxy was present at the lowest concentration. Some removal took place in the units prior to the oxidation tank, although the main reduction was observed to occur in the biological oxidation reactor. All the drugs showed a wide variability of the measured concentrations during the week and the day. Taking into account results from both full-scale observations and batch tests, removals in the biological reactor were found within the following ranges: 33-84% for AM, 33-97% for MET, 33-57% for BEG and 29-83% for THC-COOH. These removals were due to a combination of adsorption and biodegradation mainly, while volatilization did not play a significant role. Other processes, e.g. hydrolysis, were likely to occur.

A study through batch tests on the analytical determination and the fate and removal of methamphetamine in the biological treatment of domestic wastewater.

Methamphetamine (MET) is one of the most used illicit drugs in Europe and is recognized as one of the Emerging Organic Micropollutants. It is discharged into the sewerage system from different sources and then enters the wastewater treatment plants. The present study aimed at providing a better knowledge of the fate of MET through the wastewater treatment plants. The study addressed two different issues: (1) optimization of the analytical methods for MET determination in both liquid and sludge phases, focusing on the effects of potentially interfering substances and (2) investigation on the behaviour of MET in the biological treatment process, with specific concern for the biomass activity at different drug concentrations. Results of the study on issue 1 highlighted that the applied analytical method for MET determination (UPLC-MS/MS) is affected by the main components of wastewater for about 9-23%, which is comparable with the uncertainties of the method (about ± 28%). The method showed also to be repeatable and reliable (recovery > 75%; repeatability < 10-15%; bias uncertainty < 30%), and relatively easy-to-use. Therefore, it can be considered suitable for measurements on routine base in the WWTPs. Batch tests conducted to address issue 2 showed total removal of 84, 90, and 96% at 50, 100, and 200 ng/L initial MET concentration, respectively, for a contact time of 6 h. The removal process was mainly ascribed to the biological activity of both heterotrophic and autotrophic bacteria. The pseudo first-order kinetic model provided the best fitting of the experimental data of the overall biological processes at all the tested concentrations. Furthermore, the respirometric tests showed that MET does not induce any inhibition. Adsorption of MET on activated sludge was always very low.

A parametric response surface study of fermentative hydrogen production from cheese whey.

Batch factorial experiments were performed on cheese whey+wastewater sludge mixtures to evaluate the influence of pH and the inoculum-to-substrate ratio (ISR) on fermentative H2 production and build a related predictive model. ISR and pH affected H2 potential and rate, and the fermentation pathways. The specific H2 yield varied from 61 (ISR=0, pH=7.0) to 371L H2/kg TOCwhey (ISR=1.44gVS/g TOC, pH=5.5). The process duration range was 5.3 (ISR=1.44gVS/g TOC, pH=7.5) - 183h (ISR=0, pH=5.5). The metabolic products included mainly acetate and butyrate followed by ethanol, while propionate was only observed once H2 production had significantly decreased. The multiple metabolic products suggested that the process was governed by several fermentation pathways, presumably overlapping and mutually competing, reducing the conversion yield into H2 compared to that expected with clostridial fermentation.

Potential of compost mixed with tuff and pozzolana in site restoration.

The present research is aimed at evaluating the potential of mixtures made of different percentages of compost (10%, 20% and 30% by volume) and inorganic waste from extraction activities (tuff and pozzolana) for site restorations. The materials alone and the mixtures were characterised from a geotechnical point of view, in order to determine the optimal percentage to be used. In particular, the oedometric test and the direct shear test were performed. Also the environmental quality of the materials was investigated through chemical characterisation and a leaching test. In addition, a lab-scale seeding test was carried out to assess the potential phytotoxicity of the mixture. Finally, at the end of the experimentation the accumulation of heavy metals in the plants was determined and the plants+artificial soil system underwent a shear stress test. The presence of compost in the percentages tested did not reduce the mechanical performances of the inorganic residues, guaranteeing good resistance and stability. In fact, the response to oedometric compression, the compression coefficient and the internal friction angle of the mixtures were quite similar to those obtained for tuff and pozzolana alone. The mixtures selected as optimal from a mechanical point of view (30% by volume of compost and 70% by volume of tuff/pozzolana), did not represent a potential hazard for the environment due to the low content and negligible leachability of heavy metals. In addition, such mixtures can provide a good substrate for revegetation thanks to the high content of organic matter and the absence of phytotoxic effects in the conditions tested.

The influence of slaughterhouse waste on fermentative H2 production from food waste: preliminary results.

The aim of this study was to evaluate the influence of slaughterhouse waste (SHW; essentially the skin, fats, and meat waste of pork, poultry, and beef) in a fermentative co-digestion process for H2 production from pre-selected organic waste taken from a refectory (food waste [FW]). Batch tests under mesophilic conditions were conducted in stirred reactors filled with different proportions of FW and SHW. The addition of 60% and 70% SHW to a mixture of SHW and FW improved H2 production compared to that in FW only, reaching H2-production yields of 145 and 109 ml g VS 0(-1), respectively, which are 1.5-2 times higher than that obtained with FW alone. Although the SHW ensured a more stable fermentative process due to its high buffering capacity, a depletion of H2 production occurred when SHW fraction was higher than 70%. Above this percentage, the formation of foam and aggregated material created non-homogenous conditions of digestion. Additionally, the increasing amount of SHW in the reactors may lead to an accumulation of long chain fatty acids (LCFAs), which are potentially toxic for anaerobic microorganisms and may inhibit the normal evolution of the fermentative process.

The potential of compost-based biobarriers for Cr(VI) removal from contaminated groundwater: column test.

This paper presents the results of a column reactor test, aiming at evaluating the performance of a biological permeable barrier made of low-cost waste materials, for Cr(VI) removal from contaminated groundwater. A 1:1 by volume mixture of green compost and siliceous gravel was tested as reactive medium in the experimental activity. A 10mg/l Cr(VI) contaminated solution was used and the residual Cr(VI) concentration along the column height and in the outlet was determined in the water samples collected daily. Also pH, redox potential and COD were analyzed. At the end of the test, the reactive medium was characterized in terms of Cr(VI) and total chromium. The Cr(VI) removal efficiency was higher than 99% during the entire experimental activity. The influence of the biological activity on Cr(VI) removal efficiency was evaluated by varying the organic carbon and nitrogen dosages in the contaminated solution fed to the system; a removal decrease was observed when the organic carbon was not enough to sustain the microbial metabolism. The Cr(VI) removal was strictly linked to the biological activity of the native biomass of compost. No Cr(III) was detected in the outlet: the Cr(III) produced was entrapped in the solid matrix. Two main processes involved were: adsorption on the organic-based matrix and reduction into Cr(III) mediated by the anaerobic microbial metabolism of the bacteria residing in green compost. Siliceous gravel was used as the structure matrix, since its contribution to the removal was almost negligible. Thanks to the proven efficiency and to the low-cost, the reactive medium used can represent a valid alternative to conventional approaches to chromium remediation.

Co-landfilling of pretreated waste: disposal and management strategies at lab-scale.

The present paper deals with the possible advantages that can be obtained by co-landfilling of municipal solid waste organic fraction (MSWOF) and bottom ash (BA) from the incineration of municipal solid waste. In particular, the aim of the research hereby presented is to check the effect exerted by different disposal (mixed or layered) and management strategies (anaerobic or semiaerobic conditions) for landfills in which MSWOF and BA are co-disposed. Three lab-scale reactors were set-up: the reactor A with mixed BA and MSWOF in anaerobic conditions, the reactor B with mixed BA and MSWOF in semiaerobic conditions, the reactor C with layered BA and MSWOF in anaerobic conditions. The results obtained showed that the aeration at the beginning of the experimental period for about 60 days led to a more rapid biodegradation of the organic matter and to an improved leachate quality in terms of both organic load and nitrogen content. Also a significant increase in the settling rate was observed at the end of the aeration phase. Therefore, the aerobic management can be advised as the most available strategy providing a more rapid biological and mechanical stabilization of the bulk waste. Otherwise, the disposal strategy did not exert any significant effect on the leachate characteristics; however, the layered configuration may be adopted in order to accelerate the main settlements.

Pretreated waste landfilling: relation between leachate characteristics and mechanical behaviour.

The present paper presents a part of a wider research effort aiming at studying the long-term behaviour of different pre-treated wastes once landfilled; in particular, this paper deals with the analysis of settlements and their correlation with the main leachate biochemical parameters (BOD, COD and pH). The municipal solid waste organic fraction (MSWOF) and bottom ash (BA) from incineration of municipal solid waste (MSW) were considered in the study and used to set up different semi-pilot landfill plants. Particularly, the FT plant contained 90 days aerobically biostabilized MSWOF, the FP plant was filled with 15 days aerobically biostabilized MSWOF and the MX plant with a 30-70% (by weight) mixture of BA and the same MSWOF used in the FP plant. The data obtained showed a faster mechanical and biological stabilization of the FT and MX plants, due to the less biodegradable organic fraction content initially present in the FT plant and to the presence of BA, having a stabilizing effect, in the MX plant. Besides, similar behaviour of FT and MX was observed, and also a strong correlation between the settlement and the biochemical parameters time profiles was identified.

Modeling of chlorophenols competitive adsorption on soils by means of the ideal adsorbed solution theory.

The adsorption of 3-chlorophenol (3-CP) and 3,5-dichlorophenol (3,5-CP) on two Italian soils was studied at 20 degrees C. Experiments on the pure components showed that 3,5-CP was more strongly adsorbed than 3-CP, and that the adsorption capacity could be related to the organic carbon fraction of the soil. Competitive adsorption data were described by the fully predictive ideal adsorbed solution (IAS) theory. To this end, the Langmuir parameters determined from pure component adsorption data were used. Results showed that at low 3,5-CP concentration (up to 5-10 mM) the model describes satisfactorily the binary system behavior, whereas at higher concentrations predictions fail, suggesting that non ideality effects in the adsorbed phase should be accounted for.