Mercury removal from water using activated carbons derived from organic sewage sludge

Various types of activated carbons were developed from organic sewage sludge (SS) using H(2)SO(4), H(3)PO(4) and ZnCl(2) as chemical activation reagents, and the removal of Hg(II) from aqueous solution by these carbons was effectively demonstrated. The quality of the activated carbons was dramatically improved owing to chemical activation. ZnCl(2) activated carbon had the highest capability for Hg(II) adsorption, followed by H(3)PO(4) and H(2)SO(4) activated carbons. The adsorption was greatly affected by Hg(II) concentration, solution pH and carbon dosage, and followed Lagergren first order rate equation and Freundlich isotherm model. Desorption results indicated that around 60% to 80% of the adsorbed Hg(II) could be recovered from the carbons to 0.1 M HNO(3) solution by sonication treatment. Accordingly, it is believed that the activated carbons developed in this study are effective and practical for utilization in industrial wastewater treatment for mercury removal.     

Batch and column adsorption of herbicide fluroxypyr on different types of activated carbons from water with varied degrees of hardness and alkalinity

There has been little research into the effects of the water hardness and alkalinity of surface waters on the adsorption of herbicides on activated carbons. The aim of this study was to determine the influence of these water characteristics on fluroxypyr adsorption on different activated carbons. At low fluroxypyr surface concentrations, the amount adsorbed from distilled water was related to the surface hydrophobicity. Surface area of carbons covered by fluroxypyr molecules ranged from 60 to 65%. Variations in fluroxypyr solubility with water hardness and alkalinity showed a salting-in effect. Calcium, magnesium and bicarbonate ions were adsorbed to a varied extent on the activated carbons. The presence of fluroxypyr in solution decreased their adsorption due to a competition effect. K_F from the Freundlich equation linearly increased with water hardness due to salt-screened electrostatic repulsions between charged fluroxypyr molecules. The amount adsorbed from distilled water was largest at high fluroxypyr solution concentrations, because there was no competition between inorganic ions and fluroxypyr molecules. The column breakthrough volume and the amount adsorbed at breakthrough were smaller in tap versus distilled water. Carbon consumption was lower with activated carbon cloth than with the use of granular activated carbon.     

Leaching heavy metal from deposits of heavy metals with bacteria oxidizing elemental sulphur

Experiments were carried out on bacterial leaching heavy metals from aerobically stabilize excessive activated silt of Bortnichi Aeration Station of Kiev when adding elementary sulphur as a stimulant of the activity of acidophilic thiobacilli. It has been shown that a decrease of silt pH in the course of the process is a decisive factor of efficiency of leaching heavy metals.     

ENVIRONMENTAL AND STRUCTURAL IMPLICATIONS FOR THE RE-USE OF TYRES IN FLUVIAL AND MARINE-CONSTRUCTION PROJECTS

There is increasing interest in reclaiming tyres for use in bank-side and coastal-protection structures. However, concern has been expressed about the potential for tyres to release pollutants into the environment and to retain their long-term structural stability. This paper describes laboratory leaching tests for heavy metals from new used tyres and tyres which have been exposed to an aquatic environment for thirteen years. The results show that the limiting factor to their use could be cadmium release. Tests found evidence of the loss of ultraviolet screening agents such as carbon black, suggesting that chemical breakdown of the tyre through leaching of vulcanising chemicals is more significant in the physical breakdown of the tyre, than the reverse. Three case studies of tyre flood-protection and river-control structures are presented, which examine the ability of tyres to retain structural integrity over long periods. Based on this evidence, guidance on design principles is offered. It is concluded that tyres can be used sustainably in a river or coastal environment, subject to careful consideration of local site conditions.     

The regeneration of field-spent granular-activated carbons.

The thermal regeneration of field-spent granular-activated carbons (GAC) is being increasingly adopted as a cost-effective alternative to disposal. The success of this practice requires the adjustment of process conditions to maximise the recovery of the original carbon characteristics while minimising carbon loss. This paper describes an investigation into the regeneration of several field-spent GAC representative of those typically generated by the drinking water treatment industry. The carbons were initially investigated for their ash contents and inorganic compositions in order to determine the accumulation of metallic species that affect the regeneration process. Regeneration was conducted in steam at 800 degrees C over reaction times between 0 and 60 min in order to achieve different degrees of carbon gasification. Weight losses were determined for each condition and the resulting carbons characterised for their apparent density, porosity, surface area and aqueous adsorption characteristics. Results showed that spent carbons recovered most of their adsorption characteristics when heated to 800 degrees C under inert conditions. Steam gasification in the range of 5-10 wt% burn-off had some positive effects on the characteristics of the spent carbons which were in most cases counteracted by a reduction in the carbon yield. Steam gasification in excess of 15 wt% burn-off caused a rapid increase in the carbon mesoporosity but a significant deterioration in the carbon microporosity, BET surface area and adsorption capacity for organic species of small molecular size.     

饮用水处理中活性炭选择的试验研究

针对特征原水水质,选取5种不同种类的活性炭进行了最优活性炭种的筛选研究.试验结果表明：活性炭的吸附性能指标和动态试验是评价其吸附性能的有效方法;从形成生物活性炭的角度考虑,利用电镜技术评价活性炭对微生物的适用性是必要的.通过分析5种活性炭的吸附性能指标值,并结合电镜观察和动态试验结果,确定强度较高、表面粗糙（适于挂膜）的柱状炭C是最优炭种.     

Determination of physical and chemical properties of waste tyres in usage/storage areas

Used tyres interact with soil, water and the atmosphere during temporary or permanent storage and also when used as additive or paving materials in landscapes, asphalt, concrete and for coastal protection. Various organic and inorganic compounds can penetrate into the environment from used tyres at various rates dependent on climatic and soil conditions. In this study, laboratory leaching batch experiments were conducted to determine the heavy metals and other constituents that could possibly penetrate into the leachate created during tyre usage/storage. The results obtained in this study showed that tyres were dissolved due to their usage and the climatic and environmental conditions thus leading to soil and groundwater pollution in their usage/reuse/storage/disposal areas. Zinc concentrations were the highest among the heavy metals measured in the simulated leachate. The average weight loss for all tyre samples was calculated as 3.6‰.     

根据水质处理效果和吸附指标判断活性炭的更新周期

从水质处理效果和吸附指标两个方面对果园桥水厂两种规格活性炭的使用情况进行了系统分析，探讨了活性炭在净水过程中与水质、吸附指标的相关性，以此制定相应的更新方案，为今后的运行管理提供借鉴。     

Adsorption of phenol and reactive dye from aqueous solution on activated carbons derived from solid wastes

Activated carbons were produced from several solid wastes, namely, waste PET, waste tires, refuse derived fuel and wastes generated during lactic acid fermentation from garbage. Activated carbons having various pore size distributions were obtained by the conventional steam-activation method and via the pre-treatment method (i.e., mixture of raw materials with a metal salt, carbonization and acid treatment prior to steam-activation) that was proposed by the authors. The liquid-phase adsorption characteristics of organic compounds from aqueous solution on the activated carbons were determined to confirm the applicability of these carbons, where phenol and a reactive dye, Black5, were employed as representative adsorbates. The hydrophobic surface of the carbons prepared was also confirmed by water vapor adsorption. The characteristics of a typical commercial activated carbon were also measured and compared. It was found that the activated carbons with plentiful mesopores prepared from PET and waste tires had quite high adsorption capacity for large molecules. Therefore they are useful for wastewater treatment, especially, for removal of bulky adsorbates.     

Adsorption of Cr(III) on ozonised activated carbon. Importance of Cpi-cation interactions

The adsorption of Cr(III) in aqueous solution was investigated on a series of ozonised activated carbons, analysing the effect of oxygenated surface groups on the adsorption process. A study was carried out to determine the adsorption isotherms and the influence of the pH on the adsorption of this metal. The adsorption capacity and affinity of the adsorbent for Cr(III) increased with the increase in oxygenated acid groups on the surface of the activated carbon. These findings imply that electrostatic-type interactions predominate in the adsorption process, although the adsorption of Cr(III) on the original (basic) carbon indicates that other forces also participate in the adsorption process. Thus, the ionic exchange of protons in the -Cpi-H3O(+) interaction for Cr(III) accounts for the adsorption of cationic species in basic carbons with positive charge density. Study of the influence of pH on the adsorption of Cr(III) showed that, in each system, the maximum adsorption occurred when the charge of the carbon surface was opposite that of the species of Cr(III) present at the pH of the experiment. These results confirmed that electrostatic interactions predominate in the adsorption process.     

Selection and evaluation of adsorbents for the removal of anionic surfactants from laundry rinsing water

Low-cost adsorbents were tested to remove anionic surfactants from laundry rinsing water to allow re-use of water. Adsorbents were selected corresponding to the different surfactant adsorption mechanisms. Equilibrium adsorption studies of linear alkyl benzene sulfonate (LAS) show that ionic interaction results in a high maximum adsorption capacity on positively charged adsorbents of 0.6-1.7 gLAS/g. Non-ionic interactions, such as hydrophobic interactions of LAS with non-ionic resins or activated carbons, result in a lower adsorption capacity of 0.02-0.6 gLAS/g. Negatively charged materials, such as cation exchange resins or bentonite clay, have negligible adsorption capacities for LAS. Similar results are obtained for alpha olefin sulfonate (AOS). Cost comparison of different adsorbents shows that an inorganic anion exchange material (layered double hydroxide) and activated carbons are the most cost-effective materials in terms of the amount of surfactant adsorbed per dollar worth of adsorbent.     

Activated carbon adsorption of trichloroethylene (TCE) vapor stripped from TCE-contaminated water

Ground water contaminated with trichloroethylene (TCE) used in electronic, electric, dry cleaning and the like industries is often treated by air-stripping. In this treatment process, TCE in its vapor form is stripped from ground water by air stream and sometimes emitted into the atmosphere without any additional treatments. Activated carbon adsorption is one of the practical and useful processes for recovering the TCE vapor from the exhaust air stream. However, adsorption of the TCE vapor from the stripping air stream onto activated carbons is not so simple as that from dry air, since in the exhaust air stream the TCE vapor coexists with water vapor with relatively high concentrations. The understanding of the adsorption characteristics of the TCE vapor to be adsorbed on activated carbon in the water vapor-coexisting system is essential for successfully designing and operating the TCE recovery process. In this work, the adsorption equilibrium relations of the TCE vapor adsorption on activated carbons were elucidated as a function of various relative humidity. Activated carbon fibers (ACFs) were used as model activated carbon. The adsorption equilibrium relations were studied by the column adsorption method. The adsorption isotherms of TCE vapor adsorbed on sample ACFs were successfully correlated by the Dubinin-Radushkevich equation for both cases with and without coexistent water vapor. No effects of coexistent water vapor were found on the limiting adsorption volume. However, the adsorption characteristic energy was significantly reduced by the coexistence of water vapor and its reduction was successfully correlated with the equilibrium amount of water vapor adsorbed under the dynamic condition.     

炭龄对活性炭工艺去除南水北调水中有机物的影响

基于北方某水厂中试基地,采用新炭、2.5~3.5年炭、4.5~5.5年炭等不同炭龄的活性炭滤柱,进行为期1年的连续运行,对比研究炭龄对南水北调水源水中有机物去除效果的影响。结果表明,长期运行稳定的活性炭滤柱,主要通过生物作用去除水中的有机物;2.5~3.5年和4.5~5.5年炭龄滤柱对有机物的去除效果差异较小,但二者对三氯甲烷的去除效果优于生物膜不稳定的新炭滤柱;通过高通量测序解析发现,鞘氨醇单胞菌、DSSF69等是优势功能菌,炭龄长的生物多样性更丰富,生物膜系统更稳定。此外,活性炭滤柱对有机物的去除效果与进水有机物的污染程度相关,当进水溶解性有机物浓度较低时,活性炭滤柱会出现吸附物质逆扩散的现象,所以当水质较好时,活性炭滤池的有机物去除效果会减弱。     

Electrosorptive separation of humic substances

A method has been proposed for electrosorptive separation of humic substances, associated organic substances and cations of metals from water solutions of soil extracts. For separation we used beds of activated carbon polarized from an external EMF source. Essential differences were found in compositions of organic and inorganic substances concentrated in beds of the cathode and anode carbons. The proposed method is considered as an option of a comprehensive approach to studying the nature of humic compounds combining electrochemistry and instrumental methods of analysis.     

Scrap-tyre-rubber replacement for aggregate and filler in concrete

In this research the performance of concrete mixtures incorporating 5%, 7.5% and 10% of discarded tyre rubber as aggregate and cement replacements was investigated. Numerous projects have been conducted on replacement of aggregates by crumb rubbers but scarce data are found on cementitious filler addition in the literature. Hence to examine characteristics of tyre crumb-containing concrete, two sets of concrete specimens were made. In the first set, different percentages by weight of chipped rubber were replaced for coarse aggregates and in the second set scrap-tyre powder was replaced for cement. Selected standard durability and mechanical test were performed and the results were analysed. The mechanical tests included compressive strength, tensile strength, flexural strength and modulus of elasticity. The durability tests included permeability and water absorption. The results showed that with up to 5% replacement, in each set, no major changes on concrete characteristics would occur, however, with further increase in replacement ratios considerable changes were observed.     

Arsenic removal by iron-modified activated carbon

Iron-impregnated activated carbons have been found to be very effective in arsenic removal. Oxyanionic arsenic species such as arsenate and arsenite adsorb at the iron oxyhydroxide surface by forming complexes with the surface sites. Our goal has been to load as much iron within the carbon pores as possible while also rendering as much of the iron to be available for sorbing arsenic. Surface oxidation of carbon by HNO3/H2SO4 or by HNO3/KMnO4 increased the amount of iron that could be loaded to 7.6-8.0%; arsenic stayed below 10 ppb until 12,000 bed volumes during rapid small-scale tests (RSSCTs) using Rutland, MA groundwater (40-60 ppb arsenic, and pH of 7.6-8.0). Boehm titrations showed that surface oxidation greatly increased the concentration of carboxylic and phenolic surface groups. Iron impregnation by precipitation or iron salt evaporation was also evaluated. Iron content was increased to 9-17% with internal iron-loading, and to 33.6% with both internal and external iron loading. These iron-tailored carbons reached 25,000-34,000 bed volumes to 10 ppb arsenic breakthrough during RSSCTs. With the 33.6% iron loading, some iron peeled off.     

Adsorption of copper, lead and cobalt by activated carbon

The phenomena of lead, copper and cobalt adsorption by activated carbon from aqueous solution was studied in detail. Laboratory studies were conducted to evaluate and optimize the various process variables (i.e. carbon type, solution pH, equilibrium time and carbon dose). A quantitative determination of the adsorptive capacity of activated carbon to remove these metals was also determined.Significant differences were found in the ability of different types of activated carbons to adsorb lead, copper and cobalt from aqueous solution. Solution pH was found to be the most important parameter affecting the adsorption. It was found that there was practically no adsorption of lead, copper and cobalt by activated carbon below a well defined solution pH value for each metal. This critical solution pH value was found to be lower than the pH value associated with the formation of hydrolysis products. Of the ten commercially available activated carbons evaluated in these experiments, Barney Cheney NL 1266 was found to adsorb the largest percentage of lead, copper and cobalt. The adsorption of any single metal (lead, copper and cobalt) was hindered by the presence of the other metals; the metals apparently competed for adsorption sites.     

Anchorage of iron hydro(oxide) nanoparticles onto activated carbon to remove As(V) from water

The adsorption of arsenic (V) by granular iron hydro(oxides) has been proven to be a reliable technique. However, due to the low mechanical properties of this material, it is difficult to apply it in full scale water treatment. Hence, the aim of this research is to develop a methodology to anchor iron hydro(oxide) nanoparticles onto activated carbon, in which the iron hydro(oxide) nanoparticles will give the activated carbon an elevated active surface area for arsenic adsorption and also help avoid the blockage of the activated carbon pores. Three activated carbons were modified by employing the thermal hydrolysis of iron as the anchorage procedure. The effects of hydrolysis temperature (60-120 °C), hydrolysis time (4-16 h), and FeCl₃ concentration (0.4-3 mol Fe/L) were studied by the surface response methodology. The iron content of the modified samples ranged from 0.73 to 5.27%, with the higher end of the range pertaining to the carbons with high oxygen content. The materials containing smaller iron hydro(oxide) particles exhibited an enhanced arsenic adsorption capacity. The best adsorbent material reported an arsenic adsorption capacity of 4.56 mg As/g at 1.5 ppm As at equilibrium and pH 7.     

Chemical quality of bottled waters from three cities in eastern Alabama

Twenty-five brands of bottled waters consisting of both purified and spring types collected randomly from three Alabama cities, USA were assessed for their suitability for human consumption. Water quality constituents analyzed include pH, conductivity, alkalinity, chloride, nitrate + nitrite, sulfate, phosphate, total carbon (TC), inorganic carbon (IC), total organic carbon (TOC), and 27 elements on the inductively coupled plasma-optical emission spectrometer (ICP-OES). The results obtained were compared with US EPA drinking water standards and the European union (EU) drinking water directive. Ni was non-detectable in all the samples and Cu, Pb, Sb, Zn, Mn, Al, Cr, Mg, P, Ca, sulfate, chloride and nitrates + nitrites were all below their respective USEPA drinking water standards or EU maximum admissible concentrations (MAC). The conductivity, pH, As, Cd, Hg, Zn, Se and Tl values in some samples exceeded the EU and USEPA standards for drinking water. No sample had pH > 8.5, but seven bottled water brands analyzed were acidic (pH < 6.5). Most of the sampled brands had TOC concentrations exceeding 3 mg/l. The concentrations of most water quality constituents analyzed, in most cases, were higher in the spring water brands compared to the purified or distilled brands of bottled water. A one-way parametric analysis of variance (ANOVA) conducted on pH, conductivity, IC, TOC, Ca, Na, K, Mg, Se, sulfate, chloride and nitrate + nitrite values for 10 brands of bottled water to ascertain the homogeneity of variances within and between the brands, suggested significant differences in variances across the brands at a 95% confidence level except for selenium, sodium and calcium.