Stabilization of PFAS-contaminated soil with sewage sludge- and wood-based biochar sorbents.

Sustainable and effective remediation technologies for the treatment of soil contaminated with per- and polyfluoroalkyl substances (PFAS) are greatly needed. This study investigated the effects of waste-based biochars on the leaching of PFAS from a sandy soil with a low total organic carbon content (TOC) of 0.57 ± 0.04 % impacted by PFAS from aqueous film forming foam (AFFF) dispersed at a former fire-fighting facility. Six different biochars (pyrolyzed at 700-900 °C) were tested, made from clean wood chips (CWC), waste timber (WT), activated waste timber (aWT), two digested sewage sludges (DSS-1 and DSS-2) and de-watered raw sewage sludge (DWSS). Up-flow column percolation tests (15 days and 16 pore volume replacements) with 1 % biochar indicated that the dominant congener in the soil, perfluorooctane sulphonic acid (PFOS) was retained best by the aWT biochar with a 99.9 % reduction in the leachate concentration, followed by sludge-based DWSS (98.9 %) and DSS-2 and DSS-1 (97.8 % and 91.6 %, respectively). The non-activated wood-based biochars (CWC and WT) on the other hand, reduced leaching by <42.4 %. Extrapolating this to field conditions, 90 % leaching of PFOS would occur after 15 y for unamended soil, and after 1200 y and 12,000 y, respectively, for soil amended with 1 % DWSS-amended and aWT biochar. The high effectiveness of aWT and the three sludge-based biochars in reducing PFAS leaching from the soil was attributed largely to high porosity in a pore size range (>1.5 nm) that can accommodate the large PFAS molecules (>1.02-2.20 nm) combined with a high affinity to the biochar matrix. Other factors like anionic exchange capacity could play a contributing role. Sorbent effectiveness was better for long-chain than for short-chain PFAS, due to weaker, apolar interactions between the biochar and the latter's shorter hydrophobic CF2-tails. The findings were the first to demonstrate that locally sourced activated wood-waste biochars and non-activated sewage sludge biochars could be suitable sorbents for the ex situ stabilization and in situ remediation of PFAS-contaminated soil, bringing this technology one step closer to full-scale field testing.

Dataset on sinusoidally stiffened 3D printed steel plated structures.

The paper reports a series of experimental and numerical data of destructive stub column tests on additively manufactured steel parts stiffened by surface sinusoidal wave patterns. The specimens were made in 316L stainless steel and manufactured by selective laser melting (SLM). The experimental tests covered five tensile coupon tests, fourteen square hollow section (SHS) stub column tests and measurements of geometric imperfections of the stub columns. Numerical models incorporating the measured material and geometric properties were developed and analysed via GMNIA approach. The validity of the numerical models is demonstrated by their accurate replications of the load-end shortening responses of the tested specimens. The reported dataset will contribute to the stability design and characterisation of thin-walled steel plated structures with advanced stiffening patterns.

Performance assessment of the MOF adsorbent MIL-101 for removal of gaseous benzene and toluene: kinetic column modeling and simulation studies of fixed-bed adsorption.

The adsorbent MIL-101, a metal-organic framework material, was synthesized, characterized, and tested for removal of relatively low concentrations of benzene and toluene adsorbates (200 ppm) from a gas phase in a continuous flow system. Breakthrough studies were modeled based on Thomas, Yoon-Nelson, Yan, Clark, Bohart-Adams, bed-depth service time, modified dose response, Wolborska, and Gompertz in the continuous fixed-bed operation. Through statistical analysis, it was determined which type of regression is most suitable for the studied models, linear or nonlinear. By comparing the values of error functions, it was possible to infer that the Thomas model is the best match for the experimental breakthrough curves for benzene (with maximum solid-phase concentration qT=126,750 mg/g) and the Gompertz model for toluene (parameter ß=0.01 min-1). Overall, when compared to the model parameters of the linear regression, those obtained through nonlinear regression show a stronger correlation with the results found experimentally. Thus, this type of regression is more suitable for the adsorption model analysis. The liquid film and intraparticle diffusion analysis was described, and it was suggested that both types of diffusion contribute to the adsorption mechanism of benzene and toluene on MIL-101. As for the isotherms, the adsorption process was better fitted by the Freundlich isotherm. The reusability of MIL-101 after six cycles was 76.5% for benzene and 62.4% for toluene, indicating that MIL-101 was a better adsorbent for the removal of benzene in comparison with toluene.

Pilot-scale removal of persistent and mobile organic substances in granular activated carbon filters and experimental predictability at lab-scale.

Present knowledge about the fate of persistent and mobile (PM) substances in drinking water treatment is limited. Hence, this study assesses the potential of fixed-bed granular activated carbon (GAC) filters to fill the treatment gap for PM substances and the elimination predictability from lab-scale experiments. Two parallel pilot filters (GAC bed height 2 m, diameter 15 cm) with different GAC were operated for 1.5 years (ca. 47,000 BV throughput) alongside rapid small-scale column tests (RSSCT) designed based on the proportional diffusivity (PD) and the constant diffusivity (CD) approaches. Background dissolved organic matter (DOM) and a set of 17 target substances were investigated, among them 2-acrylamido-2-methylpropane sulfonate (AAMPS), adamantan-1-amine (ATA), melamine (MEL) and trifluoromethanesulfonic acid (TFMSA). Nine substances were predominantly present in the drinking water used as pilot filter influent (frequencies of detection above 80 %, median concentrations 0.003-1.868 µg/L) and their breakthrough behaviors could be observed: TFMSA was not retained at all, four substances including AAMPS and ATA reached complete breakthrough below 20,000 BV, three compounds were partially retained until the end of operation and oxypurinol was retained completely. The comparable PM candidate and DOM removal performances of both GAC aligns with their very similar surface characteristics and elemental compositions. The agreement of results between RSSCT with the pilot-scale filters were substance specific and no superior RSSCT design could be identified. However, CD-RSSCT provide a conservative removal prediction for most studied compounds. MEL adsorption was significantly underestimated by both RSSCT designs. Using the criterion of a carbon usage rate (with respect to 50 % breakthrough) below 25 mgGAC/Lwater for an economic retention by fixed-bed GAC filters, five (out of nine) substances met the requirement.

Interactions between H2O2 and dissolved organic matter during granular activated carbon-based residual H2O2 quenching from the upstream UV/H2O2 process.

Granular activated carbon (GAC) filtration can be employed to synchronously quench residual H2O2 from the upstream UV/H2O2 process and further degrade dissolved organic matter (DOM). In this study, rapid small-scale column tests (RSSCTs) were performed to clarify the mechanisms underlying the interactions between H2O2 and DOM during the GAC-based H2O2 quenching process. It was observed that GAC can catalytically decompose H2O2, with a long-lasting high efficiency (>80% for approximately 50,000 empty-bed volumes). DOM inhibited GAC-based H2O2 quenching via a pore-blocking effect, especially at high concentrations (10 mg/L), with the adsorbed DOM molecules being oxidized by the continuously generated ·OH; this further deteriorated the H2O2 quenching efficiency. In batch experiments, H2O2 could enhance DOM adsorption by GAC; however, in RSSCTs, it deteriorated DOM removal. This observation could be attributed to the different ·OH exposure in these two systems. It was also observed that aging with H2O2 and DOM altered the morphology, specific surface area, pore volume, and the surface functional groups of GAC, owing to the oxidation effect of H2O2 and ·OH on the GAC surface as well as the effect of DOM. Additionally, the changes in the content of persistent free radicals in the GAC samples were insignificant following different aging processes. This work contributes to enhancing understanding regarding the UV/H2O2-GAC filtration scheme, and promoting the application in drinking water treatment.

Dynamic Adsorption of H2S onto a Goethite-Based Material.

The use of adsorption technology to remove H2S from synthetic gas (H2S and N2) using a goethite-based adsorbent was investigated. The influence of the H2S feed concentration (150-600 mg), the adsorbent dosage (1-4 g), and the gas flow rate (210-540 cm3/min) on the breakthrough curves and H2S adsorption on the adsorbent at the breakthrough point was investigated. Dynamic column experiments were performed to provide data for the theoretical models and to verify the performance of the system in the adsorption process. The theoretical models used in the present work were found to predict the adsorption breakthrough performance reasonably well.

Water column leaching recovery manganese and ammonium sulfate from electrolytic manganese residue: extremely low water consumption toward practical applications.

Regional contamination by electrolytic manganese residue (EMR) not only composes a serious environmental problem but also leads to severe valuable resources waste. Directly recovering manganese and ammonium sulfate is a promising way, but it is still challenging to efficiently recover without high water consumption. Herein, a recovery method based on water column leaching under extremely low water consumption was firstly reported. The effect of continuous leaching and intermittent leaching on leaching behaviors, leaching trends, and spatial variations of (NH4)2SO4 and Mn with depth after leaching were fully investigated. Results indicated that some Mn-bearing soluble salts which covered on the surface of SiO2 in the micropores could be fully dissolved and transported out of the micropores in the EMR with the help of rest periods in the method of intermittent leaching, resulting in higher leaching efficiencies with comparison to continuous leaching, 73.50% of Mn and 67.71% of (NH4)2SO4 and 71.57% of Mn and 65.40% of (NH4)2SO4 were recovered by intermittent leaching and continuous leaching, respectively. This work demonstrates a practical approach to recover valuable materials from industrial solid wastes.

Assessing explicit models of per- and polyfluoroalkyl substances adsorption on anion exchange resins by rapid small-scale column tests.

Managing per- and polyfluoroalkyl substance (PFAS) contamination has gained worldwide attention due to their ubiquitous occurrence in water systems. Anion exchange resins (AERs) have been proven effective in removing both long-chain and short-chain PFASs. In this study, an explicit model was developed to describe the breakthrough behavior of an individual PFAS as a single solute onto anion exchange resin in a column filtration process. The model was further modified to predict the breakthrough curve of co-existing PFASs on AER in multi-solute systems by incorporating a separation factor describing the competitive adsorption and a blockage factor describing the loss of adsorption sites. Rapid small-scale column tests (RSSCTs) were performed with six AERs of various properties and three model PFASs in both single- and multi-solutes systems. The breakthrough behaviors of RSSCTs for both single- and multi-solute systems were found adequately described by the models developed in this study. The experiments and accompanied model simulations reveal some important relationships between the AER performance and the properties of both the AERs and the PFASs.

Understanding adsorption and biodegradation in granular activated carbon for drinking water treatment: A critical review.

Drinking water treatment plants use granular activated carbon (GAC) to adsorb and remove trace organics, but the GAC has a limited lifetime in terms of adsorptive capacity and needs to be replaced before it is exhausted. Biological degradation of target contaminants can also occur in GAC filters, which might allow the GAC to remain in service longer than expected. However, GAC biofiltration remains poorly understood and unpredictable. To increase the understanding of adsorption and biodegradation in GAC, previous studies have conducted parallel column tests that use one column of GAC (potentially biologically active) to assess overall removal via both adsorption and biodegradation, and one column with either sterilized GAC or biological non-adsorbing media to assess adsorption or biodegradation alone. Mathematical models have also been established to give insight into the adsorption and biodegradation processes in GAC. In this review, the experimental and modeling approaches and results used to distinguish between the role of adsorption and biodegradation were summarized and critically discussed. We identified several limitations: (1) using biological non-adsorbing media in column tests might lead to non-representative extents of biodegradation; (2) sterilization methods may not effectively inhibit biological activity and may affect adsorption; (3) using virgin GAC coated with biofilm could overestimate adsorption; (4) potential biofilm detachment during column experiments could lead to biased results; (5) the parallel column test approach itself is not universally applicable; (6) competitive adsorption was neglected by previous models; (7) model formulations were based on virgin GAC only. To overcome these limitations, we proposed four new approaches: the use of gamma irradiation for sterilization, a novel minicolumn test, compound-specific isotope analysis to decipher the role of adsorption and biodegradation in situ, and a new model to simulate trace organic adsorption and biodegradation in a GAC filter .

Accurate detection of reemergent anti-donor ABO antibody is crucial for safe transfusion in ABO major incompatible HSCT patient after achieved the stages of full switch to donor type.

Dynamic monitoring ABO chimera including erythroid ABO antigen and anti-A/B is crucial to not only assess the status of erythroid engraftment but also achieve personalized safety transfusion in patients post ABO incompatible hematopoietic stem cell transplantation. Transfusion support for ABO incompatible (ABOi) HSCT patients after achieved complete alteration to donor origin still remains cautious because the instant hematopoietic status on these transplant patients possibly returned to patient origin derived from early disease relapse and graft loss or failure. We reported that reemergent anti-B in a female patients (donor/patient: B/O) at the early phase after achievement complete donor type were not effectively found from partial automatic ABO blood grouping systems, which directly resulted in differential judgement of transplantation stage for about 15 days and disturbed the optimal recommendation on transfusion support. Meanwhile, the solely alteration of ABO chimera was found and earlier than changes of other markers such as MRD diagnosis, chimerism analysis by STR-PCR and sex chromosome assays, which can be an available predictors for bad transplant outcomes such as graft failure.

Remoção de carbono orgânico dissolvido de águas filtradas com tratamento complementar por pré-oxidação com ozônio e adsorção em carvão ativado / Removal of dissolved organic carbon in filtered water complemented with treatment by pre-oxidation with ozone and adsorption on activated carbon

Resumo Este trabalho teve como objetivo avaliar as remoções de carbono orgânico dissolvido presente em águas filtradas de estação de tratamento de água com tratamento complementar por pré-oxidação com ozônio e adsorção em carvão ativado granular. Para o estudo de adsorção foi utilizado o método de ensaio rápido em coluna de escala reduzida, com carvão ativado produzido de cascas de coco. Realizou-se a comparação entre as curvas de ruptura para os ensaios com e sem aplicação de ozônio. Os resultados mostraram reduções nas concentrações de carbono orgânico dissolvido no início dos ensaios e após a passagem da água com e sem pré-ozonização pelas colunas ensaio rápido em coluna de escala reduzida seguida de incrementos progressivos das concentrações à medida que se aumentou o volume de leitos tratados. Na fase final dos ensaios, os aumentos de volume de leitos tratados não causaram mudanças significativas nas concentrações efluentes de carbono orgânico dissolvido. O mesmo comportamento foi observado com relação à absorção em radiação ultravioleta a 254 nm. O uso de ozônio previamente à adsorção em carvão ativado granular, usando o método ensaio rápido em coluna de escala reduzida, resultou em maiores reduções na absorbância da luz ultravioleta em 254 nm do que nas concentrações de carbono orgânico dissolvido. As absorbâncias específicas à radiação ultravioleta das amostras ozonizadas foram menores do que as que não receberam ozônio.

Abstract The objective of this study was to evaluate the removal of dissolved organic carbon in filtered water followed by pre-oxidation with ozone and adsorption on granular activated carbon. The rapid small-scale column test was used for the adsorption essays with activated carbon produced from coconut shells. A comparison was made between the breakthrough curves for tests performed with and without pre-oxidation with ozone. The results showed reductions in dissolved organic carbon concentrations after initial passage of water with and without ozone through the rapid small-scale column test column, followed by progressive increases in concentrations along with the number of the bed volumes. In the final phase of the tests, increases in bed volumes did not cause significative changes in effluent dissolved organic carbon concentrations. The same behavior was also observed with respect to ultra-violet absorbance at 254 nm. The use of ozone prior to adsorption on GAC, using the ERCER method, caused greater reductions on UV254 absorbance than in concentrations of dissolved organic carbon. The specific ultraviolet absorbance values of samples that received ozone were lower than those that were not ozonized.

Removal of Transition Metals from Contaminated Aquifers by PRB Technology: Performance Comparison among Reactive Materials.

The most common reactive material used for the construction of a permeable reactive barrier (PRB) is zero valent iron (ZVI), however, its processing can generate corrosive effects that reduce the efficiency of the barrier. The present study makes a major contribution to understanding new reactive materials as natural and synthetic, easy to obtain, economical and environmentally friendly as possible substitutes for the traditional ZHV to be used as filters in the removal of three transition metals (Zn, Cu, Cd). To assess the ability to remove these pollutants, a series of batch and column tests were carried out at laboratory scale with these materials. Through BACH tests, four of seven substances with a removal percentage higher than 99% were prioritized (cabuya, natural clinoptilolite zeolites, sodium mordenite and mordenite). From this group of substances, column tests were performed where it is evidenced that cabuya fiber presents the lowest absorption time (≈189 h) while natural zeolite mordenite shows the highest time (≈833 h). The latter being the best option for the PRB design. The experimental values were also reproduced by the RETRASO code; through this program, the trend between the observed and simulated values with respect to the best reactive substance was corroborated.

Fixed-bed flow experiments with supported green nZVI for the remediation of contaminated waters: Effect of pH and background solution composition.

Aim of this study is to evaluate the performance of a nanocomposite material (R-nFe), consisting of nano zero valent iron (nZVI) and a cation exchange resin, for Cr(VI) reduction and heavy metals removal from contaminated water streams. The effect of pH and the background solution composition was investigated by conducting three columns tests. In Column I, the experiments were carried out using NaCl as background electrolyte while in Column II and III the background solution consisted of 50% tertiary effluents of a waste water treatment plant and 50% deionized water. The kinetics of Cr(VI) removal was found to be much faster at acidic pHs. Based on the experimental results it was calculated that the required contact time of the permeating solution with the RnFe beads for Cr(VI) removal at pH 7 is 6.5 times longer than at pH 4. The results also revealed the role of competing ions on the performance of RnFe. During the operation of the column with an inert electrolyte, such as NaCl, the RnFe bed removed an amount of Cr(VI) equivalent to 4200 mg/kg. When the column was fed with a water stream containing relatively high levels of nitrates, the RnFe removed efficiently only 190 mg/kg Cr(VI), due to the competitive consumption of nanoiron for the reduction of nitrates. The nanocomposite was found to be very efficient for the simultaneous removal of tested heavy metals, i.e. Cu, Zn, Ni, Cd and Pb, which were selectively retained in the cation exchange sites of the supporting resin matrix.

Comparing desorption properties of pollutants on bentonite particles and in compacted bentonite.

Desorption is one of the main factors causing groundwater and soil pollution. Therefore, the study of clay desorption characteristics is important for the prediction of groundwater and soil pollution. In previous studies, batch tests and column tests were used to study the desorption characteristics of pollutants on clay. However, the desorption parameters obtained via the two test methods were often quite different. To investigate differences in the desorption characteristics of different pollutants on clay particles and in compacted clay, batch and column desorption tests were conducted using cadmium chloride, fulvic acid, and sodium phosphate as the adsorbates and bentonite as the adsorbent. It was found that the unit particle surface area desorption distribution coefficients of pollutants on bentonite particles were approximately equal to the unit pore surface area distribution coefficients of pollutants in compacted bentonite. This indicates that the desorbed amount per unit of surface area is basically consistent, regardless of whether they are sorbed on particles or in compacted bentonite. A simple formula for determining the desorption retardation factor of pollutants in compacted bentonite is presented. The results of this study provide a reference for the prediction and evaluation of groundwater and soil pollution.

Chromium Removal Using Soil Loaded with Green Iron Nanoparticles.

Chromate is considered as a serious environmental problem due its toxicity. Iron nanoparticles produced by green tea polyphenols (GT-nZVI) is a powerful reductant, which can effectively reduce Cr(VI) to Cr(III). Nano ZVI suspension was initially conceived ideal for direct injection in the contaminated aquifers. However GT-nZVI presents limited mobility in calcareous aquifers. For this reason the incorporation of nanoiron in a permeable reactive barrier was investigated as an alternative mode of GT-nZVI application. Namely an amount of soil was loaded with nZVI (0.40 mmol/g of soil) and was evaluated for Cr(VI) removal by conducting batch and column tests. Batch tests were carried out by mixing soil samples, loaded with different levels of nZVI from 0.04 to 0.40 mmol per gram, with contaminated groundwater (GW) containing 1300 ppb Cr(VI). Cr(VI) concentration dropped below detection limit within 1 day using the highest nZVI dose. Soil pre-loaded with nZVI (S-nZVI) presented also high efficiency for chromates remediation, when tested under flow conditions by conducting column tests.

Electromagnetically-vibrated solid-phase microextraction for analysis of aqueous-miscible organic compound transport in soil columns.

Current methods of sampling pore water from soil columns to determine solute concentrations are slow and require relatively large volumes. Accordingly, an electromagnetically-vibrated (EMV) solid-phase microextraction (SPME) device was evaluated for determining temporal and spatial distributions of solute pore-water concentrations (solute concentration profiles) for four organic compounds, two polar (2-hexanone, 2,4-dimethyl phenol) and two nonpolar (toluene, 1,4-dichlorobenzene), in columns packed with simulated aquifer sands with different fractions of organic carbon. In batch equilibrium extraction tests, the equilibrium extraction time of the organic compounds in aqueous mixtures decreased from 30 to less than 10 min as the frequency of electromagnetic vibration increased from zero to 250 Hz. Mixture effects were not statistically significant (p > 0.05) in the extraction process using EMV SPME. Comparisons of the solute concentration profiles within the soil columns at different elapsed times measured by pore-water samples and in situ EMV SPME extractions revealed both methods were equally effective. However, EMV SPME extraction removed no solution volume and only 0.6-14% of the solute mass removed by the pore-water sample collections, substantially minimizing disturbances to solute transport and fate. Thus, the equilibrium extraction-based calibration method using EMV SPME offers an effective approach for rapidly and accurately determining solute concentration profiles in column tests with negligible solute mass loss and minimal solution flow disturbance.

Effects of thermal boundary condition on methane oxidation in landfill cover soil at different ambient temperatures.

Microbial aerobic methane oxidation (MAMO) has been considered as an environmental-friendly method for mitigating methane emission from municipal landfill sites. Soil column has in a landfill cover under one-dimensional (1-D) condition. However, most of the published soil column tests failed to simulate 1-D heat transfer due to the use of thermal conductive boundary at the sidewall. In the present study, a heavily instrumented soil column was developed to quantify the effects of thermal boundary condition on the methane oxidation efficiency under different ambient temperatures in landfill cover soil. The sidewall of the soil column was thermally insulated to ensure 1-D heat transport as would have been typically expected in the field condition. Two soil column tests with and without thermal insulation were conducted at a range of controlled ambient temperatures from 15 to 30°C, for studying how soil moisture, matric suction, gas pressure, soil temperature and gas concentration evolve with MAMO. The test results reveal that ignoring thermal insulation in a soil column test would result in a greater loss of soil heat generation by MAMO and hence oxidation efficiency by up to 100% for the range of temperature considered. When the ambient temperature increased to 30°C (but less than the optimum temperature for MAMO), the MAMO efficiency increased abruptly at first but then decreased substantially with time, and this is likely due to the accumulation of biomass generated by MAMO.

A new method for determination of heavy metal adsorption parameters in compacted clay by batch tests.

Evaluation of adsorption properties of pollutants on artificial or natural clay strata is normally considered in investigations of soil and groundwater pollution. Batch adsorption tests can be used to obtain the adsorption parameters of clay particles; however, the results from these tests are usually very different from the adsorption of actual clay strata. If the adsorption parameters obtained by batch tests are used to directly evaluate the properties of adsorption of pollutants onto compacted clay, the predicted groundwater and soil pollution will be unsafe. Although the column diffusion tests are closer to the actual situation, they may require much more time, and diffusion and adsorption occur simultaneously in tests, making it difficult to accurately determine the adsorption parameters. To solve this problem, batch adsorption and column diffusion tests were conducted using three kinds of clay materials to investigate the mechanism of the differences in adsorption properties of heavy metal on clay particles and in compacted clay. The amount of adsorption per unit particle surface area of clay particles was found to be equal to that per unit pore surface area of compacted clay. A new simplified method was proposed to determine the adsorption parameters in compacted clay. It is easy to use and provide a reference for prediction and evaluation of soil and groundwater pollution.

Remoção do 2,4-D em amostras de águas pela adsorção em leitos fixos de carvão ativado granular em escala reduzida / Removal of 2,4-D in water samples by adsorption in fixed beds of granular activated carbon on reduced scale

RESUMO O objetivo deste trabalho foi avaliar, por meio dos testes rápidos de coluna em escala reduzida, a capacidade de adsorção do carvão ativado granular (CAG) na remoção do ácido 2,4-diclorofenoxiacético (2,4-D) em amostras de água ultrapura e de água filtrada proveniente de estação de tratamento de água. Os valores da capacidade de adsorção obtidos a partir de amostras de água ultrapura foram 67% superiores aos obtidos para água com presença de matéria orgânica natural (MON). A MON influenciou fortemente a remoção de 2,4-D competindo pelos sítios de adsorção do carvão ativado e diminuiu a capacidade de adsorção para 7,43 mg 2,4-D por grama de CAG. Para a concentração de 2,4-D no afluente igual a 7089 ± 104 µg.L-1 e relação volumeágua/volumeCAG estimado em 766, foi possível produzir água com concentração de 2,4-D inferior a 30 µg.L-1, como recomendado pela Portaria Brasileira de Potabilidade de Água, do Ministério da Saúde (Portaria MS nº 2.914/2011).

ABSTRACT The aim of this study was to assess by means of rapid tests of small-scale column the adsorption capacity of granular activated carbon (GAC) for removal of 2,4-dichlorophenoxyacetic acid (2,4-D) from samples of ultrapure water and filtered water from a water treatment plant. The adsorption capacities values obtained from distilled water samples were 67% higher than those obtained for water having natural organic matter (NOM). NOM strongly influenced the removal of 2,4-D, competing for GAC adsorption sites, and decreasing its adsorption capacity to 7 mg 2,4-D g-1 CAG. For 2,4-D concentration of 7089 ± 104 µg L-1 and the water treated volume/GAC volume at 766, it was possible to produce treated water with 2,4-D concentration less than 30 µg L-1 as recommended by Brazilian Drinking Water Legislation of the Ministry of Health (Portaria MS 2914/2011).

Adsorption of methyl tert-butyl ether (MTBE) onto ZSM-5 zeolite: Fixed-bed column tests, breakthrough curve modelling and regeneration.

ZSM-5, as a hydrophobic zeolite, has a good adsorption capacity for methyl tert-butyl ether (MTBE) in batch adsorption studies. This study explores the applicability of ZSM-5 as a reactive material in permeable reactive barriers (PRBs) to decontaminate the MTBE-containing groundwater. A series of laboratory scale fixed-bed column tests were carried out to determine the breakthrough curves and evaluate the adsorption performance of ZSM-5 towards MTBE under different operational conditions, including bed length, flow rate, initial MTBE concentration and ZSM-5 dosage, and regeneration tests were carried out at 80, 150 and 300 °C for 24 h. Dose-Response model was found to best describe the breakthrough curves. MTBE was effectively removed by the fixed-bed column packed with a ZSM-5/sand mixture with an adsorption capacity of 31.85 mg g-1 at 6 cm bed length, 1 mL min-1 flow rate, 300 mg L-1 initial MTBE concentration and 5% ZSM-5 dosage. The maximum adsorption capacity increased with the increase of bed length and the decrease of flow rate and MTBE concentration. The estimated kinetic parameters can be used to predict the dynamic behaviour of column systems. In addition, regeneration study shows that the adsorption capacity of ZSM-5 remains satisfactory (>85%) after up to four regeneration cycles.