The influence of different soil constituents on the reaction kinetics of wet oxidation of the creosote compound quinoline

Creosote contaminated sites have become a widespread problem in industrialized countries. Recently, wet oxidation using high temperature, pressure, water and oxygen followed by activated sludge treatment proved to be an efficient method for removing a wide selection of creosote compounds in contaminated soils. Wet oxidation of the creosote compound quinoline was carried out in the presence of montmorillionite, quartz and humic acid. The products derived from wet oxidation were identified and treated biologically by activated sludge testing their biodegradability. The influence on the oxidation kinetics of quinoline during wet oxidation was pH dependent. Humic acid supported the oxidation of quinoline, whereas the addition of montmorillionite and quartz had either an inhibiting effect or led only to a slight increase in oxidation. In mixtures of soil constituents, especially at low contents of humic acid, the adsorption of quinoline on montmorillionite prevented oxidation at neutral pH. Thus, alkaline extraction of both quinoline and humic acid was needed for an efficient oxidation. A proposed reaction mechanism suggests that quinoline was oxidized by hydroxyl radicals formed during the oxidation of the humic acid. A wide selection of reaction products (mainly carboxylic acids, benzene and pyridine derivatives) derived from the wet oxidation of humic acid and quinoline. The reaction products from humic acid degradation had a rate limiting effect on the wet oxidation of quinoline leaving small residues of quinoline after the treatment. On the contrary, these reaction products also improved the biodegradation of products from the quinoline oxidation due to co-digestion of carboxylic acids. Therefore, the presence of soil components (mainly humic acid) improved the combined wet oxidation and biological activated sludge treatment of quinoline.     

Adsorption equilibrium of phenol onto chemically modified activated carbon F400

In this work the adsorption of phenol solutions onto activated carbon Calgon F400 has been studied. The carbon was modified by acid treatment, using soxhlet extraction with hydrochloric acid 2N for 120 cycles. The treatment did not affect significantly the surface area of the activated carbon but affected significatively the different functional groups, and thus its adsorption properties. Tóth model reproduced satisfactorily the experimental isotherm data and an adsorption enthalpy of -17.9 kJ mol-1 was found, which indicates that the process is exothermic. The pH affected significatively to the adsorption process and an empirical polynomial equation was able to reproduce maximum capacity as a function of pH. The isotherms obtained at pH 3 and 7 are very similar and showed a higher adsorption capacity compared with that obtained at pH 13. The use of phosphate buffer solutions decreased the maximum phenol adsorption capacity, due to the competitive adsorption between the phenol and phosphates. Finally, it was demonstrated that the acid treatment introduced chloride ions into the carbon, giving it properties of ion exchanger.     

Effect of humic acid on sorption of technetium by alumina

Sorption of technetium by alumina has been studied in absence as well as in presence of humic acid using ⁹⁵Tc^m as a tracer. Measurements were carried out at fixed ionic strength (0.1 M NaClO₄) under varying pH (3-10) as well as redox (aerobic and reducing anaerobic) conditions. Under aerobic conditions, negligible sorption of technetium was observed onto alumina both in absence and in presence of humic acid. However, under reducing conditions (simulated with [Sn(II)] = 10⁻⁶ M), presence of humic acid enhanced the sorption of technetium in the low pH region significantly and decreased at higher pH with respect to that in absence of humic acid. Linear additive as well as surface complexation modeling of Tc(IV) sorption in presence of humic acid indicated the predominant role of sorbed humic acid in deciding technetium sorption onto alumina.     

Consequence of chitosan treating on the adsorption of humic acid by granular activated carbon

In this work, equilibrium and kinetic adsorption of humic acid (HA) onto chitosan treated granular activated carbon (MGAC) has been investigated and compared to the granular activated carbon (GAC). The adsorption equilibrium data showed that adsorption behaviour of HA could be described reasonably well by Langmuir adsorption isotherm for GAC and Freundlich adsorption isotherm for MGAC. It was shown that pre-adsorption of chitosan onto the surface of GAC improved the adsorption capacity of HA changing the predominant adsorption mechanism. Monolayer capacities for the adsorption of HA onto GAC and MGAC were calculated 55.8 mg/g and 71.4 mg/g, respectively. Kinetic studies showed that film diffusion and intra-particle diffusion were simultaneously operating during the adsorption process for MGAC.     

Sorption of curium by silica colloids: effect of humic acid

Sorption of curium by silica colloids has been studied as a function of pH and ionic strength using (244)Cm as a tracer. The sorption was found to increase with increasing pH and reach a saturation value of ～95% at pH beyond 5.3. The effect of humic acid on the sorption of (244)Cm onto silica was studied by changing the order of addition of the metal ion and humic acid. In general, in the presence of humic acid (2 mg/L), the sorption increased at lower pH (<5) while it decreased in the pH range 6.5-8 and above pH 8, the sorption was found to increase again. As curium forms strong complex with humic acid, its presence results in the enhancement of curium sorption at lower pH. At higher pH the humic acid present in the solution competes with the surface sites for curium thus decreasing the sorption. The decrease in the Cm sorption in presence of humic acid was found to be less when humic acid was added after the addition of curium. Linear additive model qualitatively reproduced the profile of the Cm(III) sorption by silica in presence of humic acid at least in the lower pH region, however it failed to yield quantitative agreement with the experimental results. The results of the present study evidenced the incorporation of Cm into the silica matrix.     

关于《对腐植酸类标准中一些概念的质疑与建议》 一文中提出的几个问题的探讨

《对腐植酸类标准中一些概念的质疑与建议》一文中,关于腐植酸和黄腐酸的概念、关于平均碳系数的适用性、黄腐酸的界定及分析方法、腐殖酸原料和肥料产品命名和术语的规范化、分析结果"基准"的误读及分类标准等问题提出一些不同意见进行探讨,期望有利于达到统一认识,推动腐植酸肥料标准化工作正常开展.     

Adsorption capacities of poorly crystalline Fe minerals for antimonate and arsenate removal from water: adsorption properties and effects of environmental and chemical conditions

Antimonate (Sb(V)) and arsenate (As(V)) pollution frequently occur in aqueous environment and can be absorbed by poorly crystalline Fe minerals (i.e., ferrihydrite). In this study, the adsorption capacity and rate of Sb(V) and As(V) from water with fresh ferrihydrite were compared by establishing adsorption isotherms and kinetics, and the effects of ferrihydrite dosage, solution pH and humic substances on Sb(V) and As(V) adsorption were also investigated. The adsorption isotherms results showed that the equilibrium and maximum adsorption capacities of Sb(V) on ferrihydrite were approximately equal to those of As(V) under different temperatures. The results of adsorption kinetics showed that the adsorption rate of Sb(V) derived from the pseudo-second-order equation was much lower than that of As(V). In addition, the adsorption capacity and rate of Sb(V) and As(V) were greatly affected by various ferrihydrite dosage and solution pHs. The presence of humic acid and fulvic acid (FA) significantly affected the adsorption process of Sb(V) due to competition adsorption, whereas the adsorption properties of As(V) were little affected by FA under this experimental conditions.     

The reuse of dried activated sludge for adsorption of reactive dye

Adsorption processes are alternative effective methods for removal of textile dyes from aqueous solutions. The adsorption ability of adsorbent affects by physico-chemical environment for this reason in this paper effect of initial pH, dye concentrations, temperature and dye hydrolyzation were determined in a batch system for removal of reactive dye by dried activated sludge. The Langmuir isotherm model was well described of adsorption reactive dye and maximum monolayer adsorption capacity (at pH 2) of activated sludge was determined as 116, 93 and 71mgg(-1) for 20 degrees , 35 degrees and 50 degrees C, respectively. Initial pH 2, 20 degrees C and 30min contact time are suitable for removal of reactive dyes from aqueous solutions. Activated sludge was characterized by FT-IR analysis and results showed that active sludge has different functional groups and functional groups of activated sludge are able to react with dye molecules in aqueous solution. The pseudo first-order, second-order and intraparticle diffusion kinetics were used to describe the kinetic data. The pseudo second-order kinetic model was fit well over the range of contact times and also an intra particle diffusion kinetic model was fit well but in the first 30min. The dye hydrolyzation was affected adsorption capacity of biomass and adsorption capacity of biomass decreased with dye hydrolyzation from 74 to 38mgg(-1).     

Remediation of phenol-contaminated soil by a bacterial consortium and Acinetobacter calcoaceticus isolated from an industrial wastewater treatment plant

Time-course performance of a phenol-degrading indigenous bacterial consortium, and of Acinetobacter calcoaceticus var. anitratus, isolated from an industrial coal wastewater treatment plant was evaluated. This bacterial consortium was able to survive in the presence of phenol concentrations as high as 1200mgL(-1) and the consortium was more fast in degrading phenol than a pure culture of the A. calcoaceticus strain. In a batch system, 86% of phenol biodegradation occurred in around 30h at pH 6.0, while at pH 3.0, 95.2% of phenol biodegradation occurred in 8h. A high phenol biodegradation (above 95%) by the mixed culture in a bioreactor was obtained in both continuous and batch systems, but when test was carried out in coke gasification wastewater, no biodegradation was observed after 10 days at pH 9-11 for both pure strain or the isolated consortium. An activated sludge with the same bacterial consortium characterized above was mixed with a textile sludge-contaminated soil with a phenol concentration of 19.48mgkg(-1). After 20 days of bioaugmentation, the remanescent phenol concentration of the sludge-soil matrix was 1.13mgkg(-1).     

On-line coupling of size exclusion chromatography with electrospray ionization-tandem mass spectrometry for the analysis of aquatic fulvic and humic acids

A method was developed for the analysis of humic and fulvic acids by size-exclusion chromatography-electrospray ionization-tandem mass spectrometry using a completely volatile eluent. Humic and fulvic acids were separated into three peaks. These fractions occupied different mass ranges and showed differences in the fine structure of their mass spectra. The low-molecular-weight (LMW) fraction of fulvic acids is most sensitively determined by ESI-MS, and it appears that previous results obtained by infusion-ESI-MS were primarily determined by this fulvic acid fraction. The average molecular weight of this fractions turned out to be lower than that reported from infusion-ESI-MS measurements. Its scan spectra and the product ion spectra of some of its molecular anions perfectly match those previously obtained from whole fulvic acid mixtures. Obviously, a class of well-defined polycarboxylated molecules exist that occurs in all fulvic acid fractions thus far investigated. With decreasing elution time and increasing molecular weight, detection by ESI-MS loses sensitivity as compared to the parallel UV recording, and the fine structure of the scan spectra becomes increasingly uniform for both fulvic and humic acids. The average molecular weight of the HMW fraction exceeds those values calculated from infusion experiments. Scan spectra and product ion spectra of the high-molecular-weight (HMW) fraction of both the humic and the fulvic acids suggest that the HMW fraction consists of several subunits that originate from the LMW fraction.     

Oxygen uptake rate inhibition with PACT sludge

Oxygen uptake rate (OUR) experiments were performed with sludge from six laboratory-scale, continuously fed, activated sludge and PACT reactors (sludge ages of 4-, 8-, and 12-days) to evaluate the sludge's resistance to inhibitory compounds. Three inhibitory compounds with varied ability to sorb on activated carbon were tested: 3,5-dichlorophenol (3,5-DCP, strongly adsorbed), phenol (moderately adsorbed), and zinc (poorly adsorbed). The inhibitory compound concentration that reduced the unacclimated sludge's specific oxygen uptake 50% from its maximum rate was determined (IC(50)). For the organic compounds, PACT sludge resisted acute inhibition better for all sludge ages; sorption studies indicate that phenol sorbed onto the PACT sludge could account for the IC(50) difference at the higher sludge ages. With 3,5-DCP, the 4- and 8-day-old PACT and activated sludge solids sorbed similar amounts of 3,5-DCP at concentrations near the IC(50) values, yet the PACT sludge exhibited higher IC(50) values; biomass differences may have accounted for the improved resistance to inhibition. With the poorly adsorbed zinc, no difference in IC(50) or sorption was noted with the 4-day-old sludge. For the 12-day-old sludge, the PACT sludge was much more resistant to zinc exposure, with changes in the biomass rather than sorption on carbon the apparent reason.     

褐煤腐植酸吸附铜的热力学机理

为了实现腐植酸在治理重金属污染方面的资源化应用,以褐煤中提取的腐植酸为吸附剂,研究了pH值对腐植酸吸附Cu~(2+)的影响,探讨了吸附的热力学特征和作用机理。结果表明:腐植酸对Cu~(2+)的吸附明显受pH值影响,吸附量随pH值的升高而增大,pH值约5时吸附率约为95%;吸附等温线符合R-P方程、Langmuir方程、Freundlich方程及D-R方程,与R-P方程和Langmuir方程的相关程度更高;吸附过程放热,随pH值升高吸附焓增大,吸附熵由正到负逐渐减小,吸附自由能小于零且呈减小趋势;不同pH值时吸附机理有明显的差别,pH值较低时吸附作用力主要为范德华力和氢键,pH=5时配位交换反应成为主要作用。     

Equilibrium,kinetic and thermodynamic studies on the adsorption of phenol onto graphene

Graphene, a new member of carbon family, has been prepared, characterized and used as adsorbent to remove phenol from aqueous solution. The effect parameters including pH, dosage, contact time, and temperature on the adsorption properties of phenol onto graphene were investigated. The results showed that the maximum adsorption capacity can reach 28.26 mg/g at the conditions of initial phenol concentration of 50 mg/L, pH 6.3 and 285 K. Adsorption data were well described by both Freundlich and Langmuir models. The kinetic study illustrated that the adsorption of phenol onto graphene fit the pseudo second-order model. The thermodynamic parameters indicated that the adsorption of phenol onto graphene was endothermic and spontaneous.     

Adsorption of phthalic acid and its esters onto high-area activated carbon-cloth studied by in situ UV-spectroscopy

The adsorption behavior of phthalic acid and its three esters dimethyl phthalate, diethyl phthalate and diallyl phthalate onto high-area activated carbon-cloth was studied by in situ UV-spectroscopic technique. The effect of ionization of phthalic acid on its adsorption was examined by carrying out the adsorption process in three media; water, 1 M H(2)SO(4) and 0.005 M NaOH. Maximum adsorption was observed in 1 M H(2)SO(4) and almost no adsorption in 0.005 M NaOH. These results were discussed in terms of electrostatic and dispersion interactions between the adsorbate species and the carbon-cloth surface taking the point of zero charge (pH(pzc)) of the carbon-cloth into account. The adsorption process for the phthalate species studied was found to follow the first-order rate law, and the rate constants were determined. The isotherm data for the adsorption of phthalic acid and its esters were derived experimentally and fitted to Langmuir and Freundlich isotherm equations. Both equations were found to represent the experimental isotherm data almost equally well.     

Carbon isotope composition of dissolved humic and fulvic acids in the Tokachi River system

This study reports carbon isotopic ratios (Δ(14)C and δ(13)C) of dissolved humic and fulvic acids in the Tokachi River system, northern Japan. These acids have a refractory feature and they represent the largest fraction of dissolved organic matter in aquatic environments. The acids were isolated using the XAD extraction method from river water samples collected at three sites (on the upper and lower Tokachi River, and from one of its tributaries) in June 2004 and 2005. δ(13)C values were -27.8 to -26.9 ‰ for humic and fulvic acids. On the other hand, the Δ(14)C values ranged from -247 to +26 ‰ and the average values were -170 ± 79 ‰ for humic acid and -44 ± 73 ‰ for fulvic acid. The difference was attributed to the residence time of fulvic acid in the watershed being shorter than that of humic acid. The large variation suggested that humic substances have a different pathway in each watershed environment.     

Use of electrochemical techniques to characterize methamidophos and humic acid specifically adsorbed onto Pt and PtO films

Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to study methamidophos (MAP) and humic acid (HM) specifically adsorbed onto Pt and PtO films in pH-7.0 universal buffer. The approach was found to be sufficiently selective for use in studies involving adsorption of species in environmental systems (e.g., soil minerals), typically evaluated by batch experiments and high performance liquid chromatography (HPLC) or gas chromatography (GC). The proposed method allowed quantification of active hydrogen adsorption sites blocked by HM, both when this compound is adsorbed alone or co-adsorbed with MAP. At higher amounts of MAP in the adsorption solution, the compound was co-adsorbed more effectively than HM (kept at constant concentration). In the case of sequential specific adsorption, the first compound adsorbed typically predominates over the second. EIS was more effective for determining the number of blocked active sites on Pt than CV, which was superior for PtO films.     

Mobilization and deposition of iron nano and sub-micrometer particles in porous media: a glass micromodel study

Mobilization and deposition of iron nano and sub-micrometer particles (INSMP) in a porous medium were investigated using a water-saturated glass micromodel. The deposition and detachment of INSMP in the micromodel were visualized by taking serial images and experimentally verified by analysis of breakthrough curves. This first visualization study of INSMP fate showed that there were dense aggregations at the pores as the concentration of INSMP increased. The presence of dissolved humic substances (>1 ppm) significantly reduced deposition of suspended particles and enhanced detachment of the deposited particles. The mobility of INSMP in the presence of Pahokee peat fulvic acid standard II (PPFA) was higher than for Pahokee peat humic acid standard I (PPHA) due to the presence of more aromatic groups and the molecular weight in PPFA. Interfacial energy estimation based on the DLVO theory revealed that the adsorption of humic substances onto the INSMP increased the energy barrier and reduced the depth of secondary minimum between particles. The “affinity transition” in the initial deposition of INSMP within the micromodel was observed in the presence of Pahokee peat humic substances.     

Tertiary amino groups modified macroporous crosslinked poly(styrene-co-divinylbenzene) and its oxidized adsorbent: Synthesis, characterization, and adsorption behavior

Macroporous crosslinked poly(p-vinylphenyltrimethylamine) (PVPTA) and its oxidized adsorbent (OPVPTA) were synthesized and their adsorption behaviors for phenol were comparatively studied in hexane as well as in aqueous solution. The results indicated that the adsorption was enhanced after PVPTA being oxidized, and the adsorption capacity of phenol onto OPVPTA was higher than that onto the commercial Amberlite XAD-4 resin in aqueous solution. The adsorption isotherms in hexane were fitted to Langmuir and Freundlich models, and it was found that the Freundlich model was suitable for characterizing the adsorption, whereas the correlation of the equilibrium adsorption in aqueous solution was linear. The adsorption was very sensitive to the solution pH and the optimum condition was at about the neutral solution. The adsorption thermodynamic parameters were calculated and it revealed that the adsorption was an exothermic, spontaneous, and more ordered process. Investigation of the adsorption mechanism suggested that hydrogen bonding was the primary driving force for the adsorption.     

Adsorption of phenol by MMT-CTAB and WPT-CTAB: Equilibrium,kinetic, and thermodynamic study

In this study, the phenol adsorption capacity of cetyltrimethylammonium bromide modified clays (MMT-CTAB) and cetyltrimethylammonium bromide modified pulp tea (WPT-CTAB) were studied. In batch adsorption experiments performed with MMT-CTAB, the effects of parameters such contact time, phenol concentration, pH of solution and adsorbent dosage were investigated. The effect of temperature on phenol adsorption onto MMT-CTAB and WPT-CTAB was examined; equilibrium and thermodynamic studies were completed. The highest phenol removal was found at pH 4.0 for MMT-CTAB and WPT-CTAB. To analyze the kinetics of phenol adsorption onto MMT-CTAB, the pseudo first-order and pseudo second-order kinetic models were applied. The kinetic data fitted better to the pseudo second-order model than the pseudo first-order kinetic model for MMT-CTAB. The characterization of adsorbents in phenol adsorption was clarified with the FTIR technique. Thermodynamic parameters such as ΔH°, ΔS° and ΔG° were calculated for each adsorption process. The adsorption process was found to be exothermic and spontaneous for phenol adsorption by MMT-CTAB and WPT-CTAB. The results were analyzed with the Langmuir, Freundlich, Temkin and Harkins–Jura equations using linearized correlation coefficients at different temperatures. The Langmuir equation was found to best represent the equilibrium data for phenol adsorption onto MMT-CTAB and WPT-CTAB.