Suppressive effect of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and dioxin-like polychlorinated biphenyls transfer from feed to eggs of laying hens by activated carbon as feed additive

In this study, we investigated the suppressive effect of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DL-PCBs) transfer from the feed to the eggs of laying hens by using activated carbon as a feed additive. Four groups of six hens (White Leghorn egg-layers; age, 11 weeks) were housed as two control groups and two exposure groups for a period of 20 weeks. Two control groups were fed with either the basal feed “Control” or basal feed additing activated carbon “Control + C”. Another two exposure groups were fed with feed contaminated (about 6 ng TEQ kg⁻¹ feed) by standard solutions of PCDDs/PCDFs and DL-PCBs “Exposure” alone and contaminated feed adding activated carbon “Exposure + C”. There was no significant effect on each groups for the growth rate, biochemical blood components, and egg production: these were around the standard levels for poultry in general. Moreover the results in this study showed the availability of activated carbon as a feed additive owing to the reduction in the risk of food pollution by PCDDs/PCDFs and DL-PCBs. The concentration in the eggs of the Exposure group gradually increased following the start of egg-laying but reached a steady state after about 1 month. In contrast, the concentration for the Exposure + C group was stationary and below the maximum EU level (6 pg TEQ g⁻¹ fat). In comparison to the Exposure group, the Exposure + C group showed a significant decline in the percentage of bioaccumulation into the egg. This reduction due to activated carbon was also observed in the muscle and abdominal fat. The reductions were compound- and congener-dependent for DL-PCBs as follows: PCDDs/PCDFs, non-ortho-PCBs, and mono-ortho-PCBs were more than 90%, 80%, and 50%, respectively, irrespective of the type of tissues. Fat soluble vitamin concentrations in the eggs of the Exposure + C group showed lower trends than the Exposure group. The γ-tocopherol and α-tocopherol concentrations in eggs of Exposure + C group showed a significant reduction of about 40%. However, the addition of activated carbon into animal feed could obviate the remote potential for accidents causing unintentional food pollution with PCDDs/PCDFs and DL-PCBs.     

Influences of influent carbon source on extracellular polymeric substances (EPS) and physicochemical properties of activated sludge

It is necessary to understand the bioflocculation, settling and dewatering characteristics in the activated sludge process in order to establish more efficient operational strategies. The influences of carbon source on the extracellular polymeric substances (EPS) and flocculation, settling and dewatering properties of the activated sludge were investigated. Laboratory-scale completely mixed activated sludge processes were used to grow the activated sludge with different carbon sources of starch, glucose and sodium acetate. The sludge fed with acetate had highest loosely bound EPS (LB-EPS) and that fed with starch lowest. The amount of tightly bound EPS (TB-EPS), protein content in LB-EPS, polysaccharide content and protein contents in TB-EPS, were independent of the influent carbon source. The polysaccharide content in LB-EPS of the activated sludge fed with sodium acetate was lower slightly than those of starch and glucose. The sludge also had a nearly consistent flocs size and the sludge volume index (SVI) value. ESS content of the sludge fed with sodium acetate was higher initially, although it was similar to those fed with glucose and starch finally. However, the specific resistance to filtration and normalized capillary suction time fluctuated first, but finally were stable at around 5.0 × 10⁸ m kg⁻¹ and 3.5 s L g⁻¹ SS, respectively. Only the protein content in LB-EPS weakly correlated with the flocs size and SVI of the activated sludge. But there was no correlation between any other EPS contents or components and the physicochemical properties of the activated sludge.     

Preparation and characterisation of activated carbon from waste tea by physical activation using steam

ABSTRACT

In this study, the feasibility of preparing activated carbon from waste tea by physical activation using steam was investigated. The effects of activation temperature on yield and pore properties of the prepared activated carbon were studied. The yield decreased with increased activation temperature owing to the decomposition of cellulose and hemicellulose. The specific surface area and pore volume of the activated carbon were estimated using the Brunauer–Emmett–Teller method, Langmuir equation, and t-plot method. The specific surface area and micropore volume increased with increases in activation temperature, as additional volatile materials were released. The specific surface area significantly decreased at first but slightly increased with increasing activation time. The maximum specific surface area reached 995 m²/g at an activation temperature of 800 °C with a water flow rate of 0.075 g/min and a constant hold time of 0.5 hr. According to the nitrogen adsorption isotherms, micropores mainly developed when the activation temperature was below 800 °C, and both micropores and mesopores developed when it was above 800 °C. The results showed that activation temperature significantly affected micropore and mesopore volumes, as well as the specific surface area of the activated carbon. Overall, waste tea was found to be an attractive raw material for producing low-cost activated carbon.

Implications: Every year, a large amount of waste tea is generated after extraction. The high carbon content of waste tea showed that it can be used as raw material to produce activated carbon. This study investigated the feasibility of preparing activated carbon from waste tea by physical activation using steam. Temperature and time were found to have clear effects on pore properties. Our proposed method and raw material are more environmentally friendly and involve low cost. Furthermore, this offers a potential solution to the problems of waste tea disposal and low-cost activated carbon production.     

Decomposition of 2,2',4,4',5,5'-hexachlorobiphenyl with iron supported on an activated carbon from an ion-exchange resin

An activated carbon (AC) containing a high concentration (374 mg g⁻¹) of Fe was prepared by carbonization of an ion-exchange resin. To examine its chemical reactivity as a catalyst to decompose 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153), the decomposition parameters of temperature and time were varied under air or N₂. Decomposition at 350 °C was achieved within 15 min under air and 30 min under N₂, and the efficiency of PCB-153 decomposition was 99.7% and 98.0%, respectively. An analysis of inorganic chloride ions revealed that PCB-153 was mineralized effectively during the decomposition. The Brunauer-Emmett-Teller (BET) surface area and pore volume of the AC were measured to assess the adsorption capacity before and after the decomposition. The differences between decomposition under air and N₂ reflected the differences in the BET surface and pore volume measurements. A decomposition pathway was postulated, and the reactive characteristics of chlorine atoms loaded on the benzene rings followed the order of para > meta > ortho, which agrees with the calculated results from a density functional theory study.     

Production of sugarcane bagasse-based activated carbon for formaldehyde gas removal from potted plants exposure chamber

Agricultural wastes such as rice straw, sugar beet, and sugarcane bagasse have become a critical environmental issue due to growing agriculture demand. This study aimed to investigate the valorization possibility of sugarcane bagasse waste for activated carbon preparation. It also aimed to fully characterize the prepared activated carbon (BET surface area) via scanning electron microscope (SEM) and in terms of surface functional groups to give a basic understanding of its structure and to study the adsorption capacity of the sugarcane bagasse-based activated carbon using aqueous methylene blue (MB). The second main objective was to evaluate the performance of sugarcane bagasse-based activated carbon for indoor volatile organic compounds removal using the formaldehyde gas (HCHO) as reference model in two potted plants chambers. The first chamber was labeled the polluted chamber (containing formaldehyde gas without activated carbon) and the second was taken as the treated chamber (containing formaldehyde gas with activated carbon). The results indicated that the sugarcane bagasse-based activated carbon has a moderate BET surface area (557 m²/g) with total mesoporous volume and microporous volume of 0.310 and 0.273 cm³/g, respectively. The prepared activated carbon had remarkable adsorption capacity for MB. Formaldehyde removal rate was then found to be more than 67% in the treated chamber with the sugarcane bagasse-based activated carbon. The plants’ responses for this application as dry weight, chlorophyll contents, and protein concentration were also investigated.

Implications: Preparation of activated carbon from sugarcane bagasse (SCBAC) is a promising approach to produce cheap and efficient adsorbent for gas pollutants removal. It may be also a solution for the agricultural wastes problems in big cities, particularly in Egypt. MB adsorption tests suggest that the SCBAC have high adsorption capacity. Formaldehyde gas removal in the plant chambers indicates that the SCBAC have potential to recover volatile gases. The results confirmed that the activated carbon produced from sugarcane bagasse waste raw materials can be used as an applicable adsorbent for treating a variety of gas pollutants from the indoor environment.     

Adsorptive removal of an acid dye by lignocellulosic waste biomass activated carbon: equilibrium and kinetic studies

Chemically prepared activated carbon material derived from palm flower was used as adsorbent for removal of Amido Black dye in aqueous solution. Batch adsorption studies were performed for the removal of Amido Black 10B (AB10B), a di-azo acid dye from aqueous solutions by varying the parameters like initial solution pH, adsorbent dosage, initial dye concentration and temperature with three different particle sizes such as 100 μm, 600 μm and 1000 μm. The zero point charge was pH 2.5 and the maximum adsorption occurred at the pH 2.3. Experimental data were analyzed by model equations such as Langmuir, Freundlich and Temkin isotherms and it was found that the Freundlich isotherm model best fitted the adsorption data and the Freundlich constants varied from (K_F) 1.214, 1.077 and 0.884 for the three mesh sizes. Thermodynamic parameters such as ΔG, ΔH and ΔS were also calculated for the adsorption processes and found that the adsorption process is feasible and it was the endothermic reaction. Adsorption kinetics was determined using pseudo first-order, pseudo second-order rate equations and also Elovich model and intraparticle diffusion models. The results clearly showed that the adsorption of AB10B onto lignocellulosic waste biomass from palm flower (LCBPF) followed pseudo second-order model, and the pseudo second-order rate constants varied from 0.059 to 0.006 (g mg⁻¹ min) by varying initial adsorbate concentration from 25 mg L⁻¹ to 100 mg L⁻¹. Analysis of the adsorption data confirmed that the adsorption process not only followed intraparticle diffusion but also by the film diffusion mechanism.     

双氯芬酸的吸附去除过程与机制

研究了非甾体抗炎药双氯芬酸的吸附去除过程与机制。对吸附处理效果较好的活性炭与纳米羟基氧化铁（α-FeOOH）进行了比表面积、Zeta电位等表面特性的表征,研究比较了双氯芬酸在活性炭与α—FeOOH2种材料上的吸附去除效果与吸附机制。结果表明,在相同的实验条件下,活性炭与α-FeOOH对双氯芬酸吸附去除率可分别达到97．9％和84．3％;双氯芬酸在活性炭上的吸附主要是由于活性炭较大的比表面积与疏水分配作用,在α-FeOOH上的吸附主要是由于静电引力作用;活性炭与α-FeOOH对双氯芬酸的吸附去除效果均随pH的升高而降低;在pH=6时,活性炭与α-FeOOH对双氯芬酸钠的吸附等温线均符合Langmuir方程,单位饱和吸附量分别为109．98mg／g和58．96mg／g;活性炭对双氯芬酸具有更强的吸附能力。     

Adsorption of fulvic acid by carbon nanotubes from water

This study investigated adsorption of fulvic acid (FA) by single-walled (SWCNT) and multi-walled carbon nanotubes (MWCNT) and activated carbon. Adsorption of FA depends greatly on the adsorbent surface area and solution pH. SWCNT has higher adsorption than MWCNT and activated carbon. Lower E4/E6 (absorbance at 465 nm to that at 665 nm) and higher E2/E3 (absorbance at 250 nm to that at 365 nm) ratios of the residual FA in solution after adsorption than that of original FA in low pH ranges suggest that aromatic rich FA fractions with polar moieties readily adsorb on the adsorbents. The apparent interaction mechanisms between FA and CNT surfaces include electrostatic, hydrophobic, π-π and hydrogen-bond interactions. FA adsorption was reduced greatly with increasing pH because of the increase of electrostatic repulsion and the decrease of hydrophobic and hydrogen-bond interactions.     

Estimation and characterization of PCDD/Fs and dioxin-like PCBs from Chinese iron foundries

The iron foundry industry is considered to be a potential source of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This study investigated the emission factors and total emission amounts of PCDD/Fs and dioxin-like polychlorinated biphenyls (DL-PCBs) from iron foundries in China. The concentrations and the World Health Organization toxicity equivalents (WHO-TEQs) are presented and the congener profiles are discussed in this paper.In the present work, 26 fly ash samples were collected and tested to quantify the PCDD/Fs and DL-PCBs generated by 14 plants of different scales, and five stack gas samples were collected from two (named as EFG and LFG) of those plants. The emission levels of PCDD/Fs and DL-PCBs indicated that hot-air cupolas had lower emissions than cold-air cupolas. When iron ore lump and sinter were used as raw material, the emission factors were about 250 ng TEQ t⁻¹ of product. However, if the raw material was scrap, the emission factors varied owing to the different contents of organic materials in the raw materials. It was found that the mean WHO-TEQ values of PCDD/Fs and DL-PCBs were 144 and 34.2 pg Nm⁻³ in stack gas and 20.0 and 1.58 pg g⁻¹ in fly ash. In multiple tests, it was estimated that the mean emission factors of PCDD/Fs and DL-PCBs were 365 and 10.9 ng WHO-TEQ t⁻¹ released to residue and 2719 and 555 ng TEQ t⁻¹ released to air. The total emission amounts of PCDD/Fs and DL-PCBs from Chinese iron foundries with cupola furnaces released to residue and air were 16.8 and 146 g WHO-TEQ in 2008, respectively.     

The removal of uranium (VI) from aqueous solutions onto activated carbon developed from grinded used tire

In this study, activated carbon was prepared from waste tire by KOH chemical activation. The pore properties including the BET surface area, pore volume, pore size distribution, and average pore diameter were characterized. BET surface area of the activated carbon was determined as 558 m²/g. The adsorption of uranium ions from the aqueous solution using this activated carbon has been investigated. Various physico-chemical parameters such as pH, initial metal ion concentration, and adsorbent dosage level and equilibrium contact time were studied by a batch method. The optimum pH for adsorption was found to be 3. The removal efficiency has also been determined for the adsorption system as a function of initial concentration. The experimental results were fitted to Langmuir, Freundlich, and Dubinin–Radushkevich (D-R) isotherm models. A comparison of best-fitting was performed using the coefficient of correlation and the Langmuir isotherm was found to well represent the measured sorption data. According to the evaluation using the Langmuir equation, the saturated monolayer sorption capacity of uranium ions onto waste tire activated carbon was 158.73 mg/g. The thermodynamic equilibrium constant and the Gibbs free energy were determined and results indicated the spontaneous nature of the adsorption process. Kinetics data were best described by pseudo-second-order model.     

Effect of magnetic field on the removal of copper from aqueous solution using activated carbon derived from rice husk

Adsorptive removal of copper by activated carbon derived from modified rice husk (ACRH) was studied in the presence and absence of magnetic field (MF). The ACRH was prepared from the normal rice husk treated by NaOH solution and subsequent pyrolysis at 450 °C in the absence of oxygen. The physicochemical properties of ACRH's were determined before and after the adsorption process to delineate the adsorption mechanism. The BET analysis confirmed that the fabricated ACRH has a specific surface area of 8.244 m²/g with a mesopore to micropore ratio of 0.974. It was observed that the micropore structure gradually replaced the mesopores, and the surface area of the micropore increased (from 0.9219 to 4.1764 m²/g), and the pore diameter was also decreased from 180.381 to 46.249 Å after pyrolysis. The CHNO/S test result reveals that the carbon content was increased from 42 to 67.8% in the ACRH after pyrolysis. The batch sorption studies were performed by varying the initial adsorbate concentration, temperature, agitation speed, pH, adsorbent dose and contact time for magnetic and non-magnetic conditions to analyze the effect of the magnetic field. The univariate studies show that the maximum experimental adsorption capacity was 4.522 mg/g and 3.855 mg/g, respectively, for these two conditions (representing the magnetic impact) at 25 °C with an adsorbent dose of 2 g/L and an agitation speed of 150 rpm. It was also observed that the removal efficiency was 94.55% and 77.96% (magnetic and non-magnetic condition) at pH 7 with a concentration of 10 mg/L in 2 h. The test result on the impact of exposure time on the magnetic field suggested that the magnetic memory influenced the removal efficiency; after 40 to 60 min, the maximum removal efficiency was achieved, around 80 to 90%. The pseudo-second-order kinetic model was best fitted with the experimental data with a rate constant as 0.1749 and 0.1006 g/mg/min for these two conditions. The Temkin model delineates the adsorption isotherm suggesting the heat generated during the adsorption process is linearly abate with the coverage of the surface area of the adsorbent. The thermodynamic model confirms that the copper adsorption is spontaneous (ΔG = ? 3.91 kJ/mol and ? 6.02 kJ/mol), wherein the negative enthalpy value (ΔH = ? 36.74 kJ/mol and ? 25.74 kJ/mol) suggested that the process is exothermic irrespective of magnetic interference. The significant enhancement of copper removal was observed by incorporating the magnetic field, showing an increase in sorption capacity by 17.48% and a reduction of reaction time by 88.12%.

     

Nationwide monitoring of atmospheric PCDD/Fs and dioxin-like PCBs in South Korea

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) were measured in ambient air samples collected from different parts of South Korea in 2008, and the measured levels were used for assessing the spatial and temporal distribution of atmospheric PCDDFs and DL-PCBs in South Korea. The average concentrations of atmospheric PCDD/Fs and DL-PCBs among the 37 sites were 28 fg I-TEQ m⁻³ (ND ∼ 617) and 1 fg WHO-TEQ m⁻³ (ND ∼ 0.016). Elevated atmospheric levels of PCDD/Fs and DL-PCBs observed at residential/industrial sites and in the north-west of Korea, indicated a potential contribution and impacts of anthropogenic sources of PCDD/Fs and DL-PCBs. These levels were similar or lower than those previously reported in other ambient air surveys. Average concentrations of PCDD/Fs showed small seasonal variations (ANOVA analysis, p = 0.144). The highest concentrations of PCDD/Fs were observed during winter, followed by spring, autumn and summer. Atmospheric PCDD/Fs and DL-PCBs in South Korea rapidly decreased during the last 10 years (1998-2008), demonstrating the efficiency of stricter regulations and the application of best available technologies/best environmental practices at emission sources. Comparison of the congener profiles and principal component analysis showed that current atmospheric PCDD/Fs are mostly influenced by industrial sources and PCBs from old commercial PCB uses. Nationwide POPs monitoring will continue and allows an effective evaluation of the implementation of the Stockholm Convention on POPs.     

玉米芯掺杂对污泥基活性炭性能的影响

针对以城市污水厂剩余污泥为原料制备的污泥基活性炭微孔性差、比表面积低的缺陷,将一定比例玉米芯掺杂到污泥中以期改善活性炭性质。通过对活性炭的比表面积、孔结构、碘值、表面官能团测定以及表面电镜分析,探讨了不同比例玉米芯掺杂对活性炭物理化学性质的影响,并以苯酚和硝基苯为目标物,对比考察所制活性炭对有机物的吸附性能。实验结果表明,随着玉米芯掺杂比例的提高,活性炭微孔体积及比表面积明显增大,但活性炭表面官能团种类及数量变化不明显。所制活性炭表面都以酸性基团为主。结果显示苯酚和硝基苯吸附值与活性炭表面酸性基团含量关系密切,因此,玉米芯的掺杂对苯酚和硝基苯的吸附没有明显的促进作用。     

Monitoring of environmental contaminants in raw bovine milk and estimates of dietary intakes of children in South Korea

Persistent organic pollutants (POPs) are ubiquitous residual contaminants in the environment and in the food chain. Milk is an important matrix for monitoring POP contamination. This study determined the concentrations of POPs including polybrominated diphenyl ethers (PBDEs), hexachlorobenzene (HCB), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and dioxin-like polychlorinated biphenyls (DL-PCBs) in raw bovine milk, and the data was used to estimate dietary intakes in South Korea. The average concentrations of PBDEs, HCB, PCDD/Fs, and DL-PCBs in raw milk were 0.29 ng g⁻¹ fat, 0.50 ng g⁻¹ fat, 0.27 pg TEQ g⁻¹ fat, and 0.33 pg TEQ g⁻¹ fat, respectively. No significant relationship was found between the concentrations of analytes and the regions sampled. The dietary intakes of PBDEs from the consumption of milk was calculated to be 0.26, 0.10, and 0.05 ng kg⁻¹ bw d⁻¹ for the group of ages 0–6, 7–12, and 13–19, respectively. The dietary intakes of HCB was calculated to be 0.44, 0.16, and 0.09 ng kg⁻¹ bw d⁻¹ for the group of ages 0–6, 7–12, and 13–19, respectively. The dietary intakes of PCDD/Fs and DL-PCBs was calculated to be 0.78, 0.29, and 0.16 pg TEQ kg⁻¹ bw d⁻¹ for the group of ages 0–6, 7–12, and 13–19, respectively. These results indicated that the residual levels of PBDEs, HCB, PCDD/Fs, and DL-PCBs in raw bovine milk were within safe levels.     

Removal of tetrabromobisphenol A by conventional activated sludge, submerged membrane and membrane aerated biofilm reactors

The goal of this study was to compare removal efficiencies of tetrabromobisphenol A (TBBPA) using typical wastewater treatment technologies, and to identify the most significant mechanisms of removal. Two types of municipal wastewater reactors were studied: a full-scale conventional activated sludge (CAS) reactor with tertiary treatment; and three pilot-scale membrane bioreactors (MBRs) having different sludge retention times (SRTs). All four reactors were fed the same influent. A third reactor type, a membrane aerated biofilm reactor (MABR) was fed tap water, ammonia, and TBBPA. TBBPA in municipal influent ranged from 1 to 41 ng L⁻¹ (n = 10). The CAS effluent had an average TBBPA concentration of 0.7 ± 1.3 ng L⁻¹ (n = 3). Effluent concentrations from the MBRs were an average of 6 ± 6 ng L⁻¹ TBBPA (n = 26). Significant TBBPA removal was observed in the MABR throughout the 5 week of study (p ? 0.05). Removal of TBBPA from wastewater treatment was found to be due to a combination of adsorption and biological degradation. Based on experimental results, nitrification is likely a key process therein. No significant relationship between removal of TBBPA and SRT was identified (p ? 0.05).     

The pH-dependent adsorption of tributyltin to charcoals and soot

Widespread use of tributyltin (TBT) poses a serious environmental problem. Adsorption by black carbon (BC) may strongly affect its behavior. The adsorption of TBT to well characterized soot and two charcoals with specific surface area in the range of 62-111 m² g⁻¹ have been investigated with main focus on pH effects. The charcoals but not soot possess acidic functional groups. TBT adsorption reaches maximum at pH 6-7 for charcoals, and at pH > 6 for soot. Soot has between 1.5 and 15 times higher adsorption density (0.09-1.77 μmol m⁻²) than charcoals, but charcoals show up to 17 times higher sorption affinities than soot. TBT adsorption is successfully described by a new pH-dependent dual Langmuir model considering electrostatic and hydrophobic adsorption, and pH effects on TBT speciation and BC surface charge. It is inferred that strong sorption of the TBTOH species to BC may affect TBT toxicity.     

Concentration of DL-PCBs in fish from market of Parma city (north Italy): estimated human intake

The concentrations of 12 congeners of non-ortho and mono-ortho dioxin-like polychlorinated biphenyls (ΣDL-PCB) were measured in 30 fish samples from Parma markets by GC/MS technique. The samples were randomly purchased, choosing the species commonly found in supermarkets. The concentration of DL-PCBs estimated remained under the fixed Italian limit of 4 pg g⁻¹ ww WHO-TEQ (World Health Organization-Toxic Equivalent) in the major part of the samples, so the situation seems to be not at a level sufficient to pose a risk to human health of the Parma population. The medium daily intake for DL-PCBs for Italian consumers (Parma) was also estimated. This value generally resulted minor than 2 pg g⁻¹ ww WHO-TEQ kg⁻¹ body weight, exceeding only in four cases: eel, smooth hound, starry smooth hound and tuna.     

Preparation of activated carbon from dried pods of Prosopis cineraria with zinc chloride activation for the removal of phenol

Utilization of agrowaste materials for the production of activated carbon, as an excellent adsorbent with large surface area, is well established industrially, for dephenolation of wastewater. In the present work, dried pods of Prosopis cineraria—a novel and low-cost agrowaste material—were used to prepare activated carbons by zinc chloride activation. Batch adsorption experiments were carried out to study the effects of various physicochemical parameters such as initial phenol concentration, adsorbent dose, initial solution pH, and temperature. Pseudo-first-order second-order and diffusion kinetic models were used to identify the possible mechanisms of such adsorption process. The Langmuir and Freundlich equations were used to analyze the adsorption equilibrium. Maximum removal efficiency of 86 % was obtained with 25 mg?L^?1 of initial phenol concentration. The favorable pH for maximum phenol adsorption was 4.0. Freundlich equation represented the adsorption equilibrium data more ideally than the Langmuir. The maximum adsorption capacity obtained was 78.32 mg?g^?1 at a temperature of 30 °C and 25 mg?L^?1 initial phenol concentration. The adsorption was spontaneous and endothermic. The pseudo-second-order model, an indication of chemisorption mechanism, fitted the experimental data better than the pseudo-first-order Lagergren model. Regeneration of spent activated carbon was carried out using Pseudomonas putida MTCC 2252 as the phenol-degrading microorganism. Maximum regeneration up to 57.5 % was recorded, when loaded phenol concentration was 25 mg?L^?1. The data obtained in this study would be useful in designing and fabricating an efficient treatment plant for phenol-rich effluents.     

Diagnosis of dissolved organic matter removal by GAC treatment in biologically treated papermill effluents using advanced organic characterisation techniques

Granular activated carbon (GAC) exhaustion rates on pulp and paper effluent from South East Australia were found to be a factor of three higher (3.62 cf. 1.47 kg m⁻³) on Kraft mills compared to mills using Thermomechanical pulping supplemented by Recycled Fibre (TMP/RCF). Biological waste treatment at both mills resulted in a final effluent COD of 240 mg L⁻¹. The dissolved organic carbon (DOC) was only 1.2 times higher in the Kraft effluent (70 vs. 58 mg L⁻¹), however, GAC treatment of Kraft and TMP/RCF effluent was largely different on the DOC persisted after biological treatment. The molecular mass (636 vs. 534 g mol⁻¹) and aromaticity (5.35 vs. 4.67 L mg⁻¹ m⁻¹) of humic substances (HS) were slightly higher in the Kraft effluent. The HS aromaticity was decreased by a factor of 1.0 L mg⁻¹ m⁻¹ in both Kraft and TMP/RCF effluent. The molecular mass of the Kraft effluent increased by 50 g mol⁻¹ while the molecular mass of the TMP/RCF effluent was essentially unchanged after GAC treatment; the DOC removal efficiency of the GAC on Kraft effluent was biased towards the low molecular weight humic compounds. The rapid adsorption of this fraction, coupled with the slightly higher aromaticity of the humic components resulted in early breakthrough on the Kraft effluent. Fluorescence excitation-emission matrix analysis of the each GAC treated effluent indicated that the refractory components were higher molecular weight humics on the Kraft effluent and protein-like compounds on the TMP/RCF effluent. Although the GAC exhaustion rates are too high for an effective DOC removal option for biologically treated pulp and paper mill effluents, the study indicates that advanced organic characterisation techniques can be used to diagnose GAC performance on complex effluents with comparable bulk DOC and COD loads.     

Sorption, desorption, and degradation of (4-chloro-2-methylphenoxy)acetic acid in representative soils of the Danubian Lowland, Slovakia

Herbicide leaching through soil into groundwater greatly depends upon sorption-desorption and degradation phenomena. Batch adsorption, desorption and degradation experiments were performed with acidic herbicide MCPA and three soil types collected from their respective soil horizons. MCPA was found to be weakly sorbed by the soils with Freundlich coefficient values ranging from 0.37 to 1.03 mg^1−1/n kg⁻¹ L^1/n. It was shown that MCPA sorption positively correlated with soil organic carbon content, humic and fulvic acid carbon contents, and negatively with soil pH. The importance of soil organic matter in MCPA sorption by soils was also confirmed by performing sorption experiments after soil organic matter removal. MCPA sorption in these treated soils decreased by 37-100% compared to the original soils. A relatively large part of the sorbed MCPA was released from soils into aqueous solution after four successive desorption steps, although some hysteresis occurred during desorption of MCPA from all soils. Both sorption and desorption were depth-dependent, the A soil horizons exhibited higher retention capacity of the herbicide than B or C soil horizons. Generally, MCPA sorption decreased in the presence of phosphate and low molecular weight organic acids. Degradation of MCPA was faster in the A soil horizons than the corresponding B or C soil horizons with half-life values ranging from 4.9 to 9.6 d in topsoils and from 11.6 to 23.4 d in subsoils.