Removal of aluminum from some water samples by sorptive-flotation using powdered modified activated carbon as a sorbent and oleic acid as a surfactant.

Bench-scale experiments were conducted in the laboratory, aiming to remove aluminum from water. They were based on using powdered activated carbon (PAC), which was prepared from olive stones generated as plant wastes and modified with an aqueous oxidizing agent as HNO3 as an effective sorbent and oleic acid (HOL) as a surfactant. The main parameters (namely: initial solution pHs, sorbent, surfactant and aluminum concentrations, shaking time, ionic strength and the presence of foreign ions) that influence the sorptive-flotation process were examined. Good results were obtained under the optimum conditions, according to which nearly 100% of aluminum, at pH 7 and at room temperature (approximately 25 degrees C), was removed. The procedure was successfully applied to recover aluminum spiked to some natural water samples. Moreover, a sorption and flotation mechanism is suggested.     

Removal of atrazine from water using an iron photo catalyst supported on activated carbon

Atrazine is a systemic triazine herbicide, which has been classified as an endocrine disrupting pesticide of hormones and the reproductive systems of humans. Moreover, atrazine was recently considered as a potential carcinogen by several reports. The aim of this work was to synthesize and to evaluate an iron catalyst supported on activated carbon to remove atrazine from water. Five different treatment schemas were evaluated: (1) adsorption with the photocatalyst’s support alone, (2) adsorption with the supported photocatalyst alone, (3) adsorption coupled to heterogeneous Fenton reaction, (4) adsorption coupled to heterogeneous advanced oxidation with UV light and (5) adsorption coupled to heterogeneous photo assisted Fenton reaction. The photocatalyst synthesized, via the incipient wet impregnation method, showed 1176 ± 24 m²/g of Langmuir area and 1.6 % wt/wt of iron content. After 120 min of reaction time, total removal efficiencies in the treatment schemas using the photocatalyst ranged from 70 % (mainly adsorption with the photocatalyst alone) to 96 % (Adsorption and heterogeneous photo assisted Fenton reaction). The heterogeneous photo assisted Fenton reaction was the fastest and most efficient treatment schema, with results better than that reported for similar materials. The adsorption data was fitted to a kinetic model of pseudo-second order and the results of advanced oxidation process were fitted to a kinetic model of fractional order.     

Removal of organics from produced water by reverse osmosis using MFI-type zeolite membranes

Separation of an organics/water mixture was carried out by reverse osmosis using an α-alumina-supported MFI-type zeolite membrane. The organic rejection performance is strongly dependent on the ionic species and dynamic size of dissolved organics. The membrane showed high rejection efficiency for electrolytes such as pentanoic acid. An organic rejection of 96.5% with a water flux of 0.33 kg m⁻² h⁻¹ was obtained for 100 ppm pentanoic acid solution at an operation pressure of 2.76 MPa. For non-electrolyte organics, separation efficiency is governed by the molecular dynamic size; the organics with larger molecular dynamic size show higher separation efficiency. The zeolite membrane gives an organic rejection of 99.5% and 17% for 100 ppm toluene and 100 ppm ethanol, respectively, with a water flux of 0.03 kg m⁻² h⁻¹, 0.31 kg m⁻² h⁻¹ at an operation pressure of 2.76 MPa. It was observed that organic rejection and water flux were affected by the organic concentration. As pentanoic acid concentration increased from 100 ppm to 500 ppm, both organic rejection and water flux decreased slightly.     

Bioreduction of ionic mercury from wastewater in a fixed-bed bioreactor with activated carbon

Wide industrial use of mercury led to significant mercury pollution of the environment. It requires development of cleanup technologies which would allow treating large volumes of mercury contaminated water in a cost effective and environmentally friendly way. A novel bio-technology, developed from laboratory to industrial scale in Germany at HZI (former GBF), is based on enzymatic reduction of highly toxic Hg(II) to water-insoluble and relatively non-toxic Hg(0) using live mercury resistant bacteria immobilized on a porous carrier material in a fixed-bed bioreactor. Improvement of the original method was based on the use of activated carbon as a carrier for microorganisms and an adsorbent for mercury. Such integration of the process should increase the technology efficiency. In order to compare different carrier materials, activated carbon and pumice stones were used. The strain Pseudomonas putida was immobilized in bioreactors continuously fed with solutions of HgCl₂ enriched with nutrients. Simultaneously, experiments in two more reactors were run in the absence of microorganisms to investigate the influence of nutrients on the adsorption process. In the bioreactor with activated carbon, the outlet mercury concentration was approximately 50 % of that supplied with pumice. It may be concluded that the use of activated carbon in a fixed-bed bioreactor enables improvement of the technology by process integration. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

Removal of compressor oil microdroplets from water with a carbon fabric

Coalescence of KHA-30 compressor oil microdroplets on a carbon fabric, aimed to remove them from air and water streams used for compressor cooling, was examined.     

Mechanism of powdered activated carbon enhancing caproate production

Caproate, produced by microbial chain elongation process, is potential to replace the diversified fossil-based products, contributing to carbon neutrality. However, its production performance is far from industrial application, so the cost-effective enhancement measures are highly needed. This study confirmed powdered activated carbon (PAC) has a significant effect on enhancing caproate production performance. The production, yield, and selectivity of caproate were improved by more than 1-fold by the optimized PAC dosage of 15 g/L, comparing with control. Mechanism investigation from a new visual angle showed that PAC accelerated ethanol oxidation to generate acetyl-CoA, and simultaneously boosted the efficiency of reverse β oxidation (RBO) by promoting the timely reaction of butyrate and acetyl-CoA to synthesis caproate. The addition of PAC also shifted the microbial community by enriching more caproate-producing bacteria but eliminating irrelevant ones. Furthermore, metagenomic analysis revealed that PAC effectively up-regulated the functional genes encoding key enzymes responsible for ethanol oxidation and RBO pathway, which was the root cause for the improved caproate production. This study presented the intrinsic insights into the mechanism of PAC promoting caproate generation, laying a foundation to the scale production of caproate.     

Removal of trace organic compounds from multicomponent liquid mixtures. I. Adsorption of surfactant mixtures on activated carbon

This study shows how trace amounts of surfactants are adsorbed by activated carbon under competitive conditions in aqueous solution. Surfactants used as adsorbates are sodium dodecyl sulfate (SDS) and eicosaneoxyethylene hexadecyl ether (POE). Activated carbon used as an adsorbent is Pittsburgh activated carbon. Adsorption isotherms on the activated carbon were all Freundlich-type, both in the multi-solute system and in the mono-solute systems. The total adsorbed amount in the multi-solute system increases linearly with increasing molar fraction of SDS in the initial concentration. Thus, the total adsorbed amount in the multi-solute system can be estimated by the Freundlich constants, which can be determined from the single-solute equilibrium adsorptions, and molar fractions of adsorbates in the initial concentration.     

Phenol adsorption onto powdered and granular activated carbon, prepared from Eucalyptus wood

Eucalyptus grandis sawdust, a major waste from the growing Uruguayan wood industry, was used in previous work to prepare powdered activated carbon (PAC). In the present work, granular activated carbon (GAC) was prepared by mixing PAC, carboxymethyl cellulose as a binder, and kaolin as reinforcer. Ultimate analysis and surface characterization of GAC and PAC were performed. Phenol adsorption was used as a way to compare the characteristics of different PAC and GAC preparations. Kinetics and isotherms of the different GAC and PAC were performed in a shaking bath at 100 rpm and 298 K. Phenol concentrations were determined by UV spectroscopy. Some kinetics parameters were calculated; from kinetics results, external resistance to mass transfer from the bulk liquid can be neglected as the controlling step. Isotherms were fitted to Langmuir and Freundlich models, and corresponding parameters were determined. Maximum phenol uptakes for all carbons were determined and correlated with carbon characteristics. Thermogravimertic analysis (TGA) determinations were performed in order to study adsorption characteristics and conditions for GAC regeneration after its use. The results showed that phenol is preferentially physisorbed on the carbon of the granules, though some chemisorption was detected. No adsorption was detected in the kaolin-carboxymethyl cellulose mixture.     

活性炭液相吸附去除噻吩硫化物的研究

迄今为止,国内外降低汽油硫含量的方法主要有原料加氢脱硫、汽油加氢脱硫、溶剂抽提脱硫、催化裂化脱硫、氧化脱硫、生物脱硫、吸附脱硫及组合技术,同时一些非常规技术如膜过程脱硫、等离子体和光脱硫也在积极探索之中。     

Removal of phenols from water and petroleum industry refinery effluents by activated carbon obtained from coconut coir pith

Coir pith obtained from the coir industry as waste biomass was used to prepare activated carbon by chemical activation using phosphoric acid (H₃PO₄). The influences of activation temperature and lasting time of activation on specific surface areas (SSA) of the activated carbons were observed. Physical characteristics of the activated carbon were investigated using X-ray diffraction (XRD), infra-red spectroscopy (IR), surface area analyzer, scanning electron microscopy (SEM), thermal analysis and potentiometric titration. The feasibility of using activated carbon for the removal of phenol (P), p-chlorophenol (PCP) and p-nitrophenol (PNP) from water and petroleum refinery industry effluents was investigated. The effects of contact time, adsorbent dose, ionic strength and initial concentration on the adsorption of phenols onto the activated carbon were investigated. The optimum pH for the maximum removal of phenols was 6.0. The equilibrium adsorption data of phenols were correlated to Langmuir and Freundlich isotherm models, the latter being the best fit of the experimental data. Dynamics of the sorption process and mass transfer were investigated using McKay and Urano-Tachikawa models. Adsorption kinetic data fits the Urano-Tachikawa kinetic model. The utility of the adsorbent was tested by using petroleum refinery industry effluent. The adsorbed phenols can be recovered by treatment with 0.1 M NaOH solution.     

Adsorption of organics on activated carbon cloth at zero surface coverage

Summary Adsorption properties of activated carbon cloth were investigated by gas-solid chromatography. Retention of several organic compounds was measured in the temperature range from 200 to 250°C. The gas/solid distribution coefficients and the related thermodynamic function of adsorption at zero surface coverage were determined. The obtained experimental data were used to explain the adsorbent-adsorbate interaction.     

Preconcentration method for phosphate in water using activated carbon loaded with zirconium

Summary An effective and simple method for preconcentration of phosphate in aqueous solution has been developed, using activated carbon loaded with zirconium (Zr-C*). The Zr-C* was prepared by mixing 100 ml of zirconyl nitrate solution (1 g Zr, pH 1.6) with 10 g of activated carbon at 25 ° C for three days, filtering and drying the residue in air. 10 g of the resulting material included 0.5 g to 0.6 g of zirconium. The adsorption of phosphate and its desorption depend only on the pH of solution. They occur quantitatively and instantaneously at pH below 8.0 and above 13.5, respectively. An aqueous solution with the pH adjusted to 1.5 is passed through the Zr-C* bed formed on a membrane filter paper with the aid of suction. The collected phosphate is then recovered by eluting with 40 ml of 1 M sodium hydroxide solution. Pyrophosphate, tripolyphosphate and metaphosphate behave as similar as orthophosphate.

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Anreicherungsverfahren für Phosphat in Wasser unter Verwendung von Zirkonium-beladener Aktivkohle

Zusammenfassung Ein einfaches und wirkungsvolles Anreicherungsverfahren für Phosphat in wässriger Lösung beruht auf der Verwendung von Zr-beladener Aktivkohle (Zr-C*), die durch Vermischen (3 Tage) von 100 ml Zirkonylnitratlösung (1 g Zr, pH 1,6) mit 10 g Aktivkohle, Filtern und Trocknen hergestellt wurde. 10 g des Materials enthielten 0,5–0,6 g Zirkonium. Adsorption und Desorption von Phosphat sind nur vom pH-Wert der Lösung abhängig und erfolgen quantitativ bei pH < 8,0 bzw. pH > 13,5. Die wässrige Probelösung vom pH 1,5 wird durch das auf einem Membranfilterpapier befindliche Zr-C*-Bett gesaugt und das zurückgehaltene Phosphat durch Elution mit 40 ml 1 M NaOH-Lösung wiedergewonnen. Pyrophosphat, Tripolyphosphat und Metaphosphat verhalten sich ähnlich wie Orthophosphat.

     

Removal of trace Cr(VI) from water using chitosan-iron nanowires in porous anodic alumina

Chitosan-iron nanowires in porous anodic alumina (PAA) have been successfully prepared under ambient conditions as an adsorbent. The adsorbent was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and N₂-BET surface area. The results showed that PAA can disperse and protect Fe⁰ nanorods from oxidation. The adsorption characteristics of trace Cr(VI) onto adsorbent have been examined at different initial Cr(VI) concentrations with pH 5. Batch adsorption studies show that the removal percentage of adsorbent for the removal of trace Cr(VI) is strongly dependent on the initial Cr(VI) concentrations. Langmuir and Freundlich isotherm models were used to analyze the experiment data. The adsorption of trace Cr(VI) by adsorbent is well modeled by the Langmuir isotherm and the maximum adsorption capacity of Cr(VI) is calculated as 123.95 mg/g which is very closed to the experiment results. Intraparticle diffusion study shows that the intraparticle diffusion of adsorbent is not the sole rate-controlling step. The negative value of Gibbs free energy change, ΔG^o, indicated that the process of Cr(VI) onto adsorbent was spontaneous. This work has demonstrated that chitosan-iron nanowires in porous anodic alumina as an adsorbent has promising potential for heavy metal removal at trace level.     

离子液体催化脱除芳烃中微量烯烃的研究

以室温离子液体为催化剂,对芳烃中的微量烯烃杂质进行深度脱除。考察了离子液体种类、用量、温度等不同因素对烯烃脱除效果的影响。结果表明,[bmim]Br-AlCl₃离子液体显示了优良的催化性能,在离子液体的质量分数为5%、室温、反应10min下,溴指数从原料的773.5下降到10以下,芳烃中微量烯烃脱除率达到99%以上,离子液体可重复使用,并对反应机理进行了研究。     

Adsorption of some toxic elements from water samples on modified activated carbon,activated carbon and red soil using neutron activation analysis

A simple and sensitive method for the determination of some metalloids and heavy metals in water samples is presented. The method is based on the preconcentration of the attachment of chelating functionalities with metalloids and toxic metals irreversibly and targeted towards toxic metals adsorbed on modified activated carbon, activated carbon and red soil particles at pH 3.0–9.0±0.2, followed by quantitative determination using instrumental neutron activation analysis (INAA), on the absorbers. Attachment results from attraction that may be physical, chemical, electrical, or a combination of all three. The efficient removal of metalloids and toxic metals, especially arsenic, chromium and mercury is anticipated. The adsorption capacity of the chemically modified activated carbon materials was evaluated for the above mentioned metalloid and toxic metal ions in the presence of iron ions and simulated water samples. Red soil particles containing iron was utilized in the control of oxidation-reduction reaction with metalloids and toxic metals. The preconcentration of the elements of interest on red soil particles, activated carbon and modified activated carbon at different depths, pH and oxidation states was investigated. The results obtained showed good agreement with certified values giving relative errors of less than 10%.     

Preconcentration of trace elements from pure manganese and manganese compounds with activated carbon as collector

A method is described for separation of traces of Bi, Cd, Co, Cu, Fe, In, Ni. Pb, Tl, and Zn from pure manganese and manganese compounds and their determination by flame a.a.s. After the metal or manganese dioxide samples have been dissolved in acid (and manganese salts in water) the trace elements are compleed with potassium xanthogenate. The solution is then filtered through a small filter paper covered with activated carbon, whereby complex compounds are separated from the matrix. When the charcoal is treated with acid, a trace concentrate is obtained which is nearly free of manganese. The detection limits for the analysis of 10-g samples of manganese metal are <0.5 p.p.m., and for 30-g samples of MnCl₂-4H₂O are ? 0.1 p.p.m. The relative standard deviation, in general,is lower than 5%.