Sorption Filters Research Articles

Oxidized cellulose: An application in the form of sorption filter materials

AbstractOxidized cellulose (oxycellulose) was very effectively used in the form of filter sheets to remove some metal ions from water and from aqueous solutions. Furthermore, oxycellulose was applied in an ion‐exchange column and in a batch process. The mechanisms of the sorption process inside oxycellulose as well as the kinetics of sorption were studied. A comparison of oxycellulose and other adsorption components such as zeolites and ion‐exchange resins was made. The affinity of oxycellulose to metal ions was determined to be in the following order: Cd2+, Zn2+ > Ni2+ ≫ Ca2+ > Mg2+ ≫ Na+. The use of oxycellulose was very effective, especially in the form of sorption filters, because this allowed us to use a simple filtration process. Moreover, the specific loading amount of the filter cake was higher for filtration than for the column process under comparable conditions. Oxycellulose in a glass column behaved similarly to an ion‐exchange resin. It showed approximately constant efficiency until the sorption capacity of the adsorbent was exhausted, and then it suddenly dropped. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Removal of As, Cd, Cr, Cu, Ni and Zn from polluted water using an iron based sorbent

In this study fixed-bed sorption filters are filled with an iron based sorbent (ferrosorp plus, FP) and used to remove a range of heavy metals (i.e. As, Cd, Cr, Cu, Ni, and Zn) from polluted water. It is found that FP is very effective at simultaneous removal of the heavy metals, and the magnitude of heavy metal removal in a decreasing order is Cd, Ni, Cr, Zn, Cu and As. Furthermore, the effect of humic acid (HA) and light on the heavy metal removal is also tested. The data show that both the presence of 100 mg/L HA and the absence of light suppress the removal, with the suppression due to HA being more significant. A mathematical model (i.e. Thomas model) is employed to study the data further and to predict the breakthrough adsorption capacities. Accordingly, capacities of 10.57, 21.85, 15.96, 12.86, 17.54, and 11.07 μmol/g are found for As, Cd, Cr, Cu, Ni and Zn, respectively, at an average inflow pH of 6.8 and heavy metal concentration of ≈2.8 μM. It is concluded that FP has high affinity to heavy metals and it can be used (e.g. as a filter medium) to treat waters containing a wide range of heavy metals, e.g. stormwater, industrial wastewater.

Nonwoven textiles for treatment of wastewaters to remove petroleum products

The expediency of using washed polypropylene fibres with a linear density of 0.33 tex treated with an organosilicon water repellent in the amount of 7% of the weight of the fibre for production of sorption filter material was demonstrated. The nonwoven filter material is recommended for treating wastewaters and removing petroleum products from the surface of water.

Composite sorption filter bags with fibre and disperse fillers

The essence of the structure and formation of a fibre-or dispersely filled knit composite filter bag was revealed. Handbook process parameters and the results of tests on experimental samples are presented. The applicability of the technology for manufacturing sorption composite filter bags with fibre and disperse fillers was demonstrated.

Arsenate removal from water using sand–red mud columns

This study describes experiments in which sorption filters, filled with chemically modified red mud (Bauxsol) or activated Bauxsol (AB) coated sand, are used to remove As(V) (arsenate) from water. Bauxsol-coated sand (BCS) and AB-coated sand (ABCS) are prepared by mixing Bauxsol or AB with wet sand and drying. Samples of the BCS and ABCS are also used in batch experiments to obtain isotherm data. The observed adsorption data fit the Langmuir model well, with adsorption maxima of 3.32 and 1.64 mg g −1 at pH values of 4.5 and 7.1, respectively for BCS; and of 2.14 mg g −1 for ABCS at a pH of 7.1. Test results show that higher arsenate adsorption capacities can be achieved for both BCS and ABCS when using the columns compared to results for batch experiments; the difference is greater for BCS. Additional batch tests, carried out for 21 days using BCS to explain the observed discrepancy, show that the equilibrium time previously used in batch experiments was too short because adsorption continued for at least 21 days and reached 87% after 21 days compared to only 35% obtained after 4 h. Fixed bed column tests, used to investigate the effects of flow rate and initial arsenate concentration indicate that the process is sensitive to both parameters, with lower flow rates (longer effective residence times in the columns) and initial arsenate concentrations providing better column performance. An examination of the combined effect of potential competing anions (i.e. silicate, phosphate, sulphate and bicarbonate) on the column performance showed that the presence of these anions in tap water slightly decreases arsenate removal. Each breakthrough curve is compared to the Thomas model, and it is found that the model may be applied to estimate the arsenate sorption capacity in columns filled with BCS and ABCS. The data obtained from both batch and column studies indicate that BCS and ABCS filtration could be effectively used to remove arsenate from water, with the latter being more efficient.

Emanation-Thermal Analysis of Fibrous Basalt Sorbents

Structural changes in basalt sorbents in the course of thermal treatment were studied by complex emanation-thermal analysis. Sorbent was prepared by two-stage treatment of staple basalt fibers with hydrochloric acid. The sorption isotherms of liquid nitrogen vapor on these new sorbents were obtained, the open surface areas were determined, and the porosity and pore size distribution of leached fibers were evaluated. The data of thermostimulated gas liberation method showed that water sorbed on porous basalt fibers occurs in two energy-different states: the main fraction of water is desorbed at 90-110°C, and the remainder, at 300-320°C. The sorbent is completely regenerated on heating to 550°C. Degradation of the fiber pore structure begins at 700°C, and fiber sintering, at temperatures greater than 1150°C. A mathematical model of emanation of the porous systems in the sintering mode was proposed, and the activation energies of emanation of the initial and porous fibers were calculated. It was found that leaching, along with formation and development of the mesopore system, generates numerous “point” defects. Due to significant sorption activity and high thermal stability, fibrous basalt sorbents can be recommended to prepare sorption filters for treatment of radiochemical production wastes.

Screening of commercial sorbents for the removal of reactive dyes

Sorption filters could be a relatively simple treatment step to remove reactive dyes from textile wastewater. Activated carbon is already used in some treatment plants (loadings approx. 100 mg g −1), and many non-regenerable products have been tested. This study aimed at identifying suitable sorbents for on-site regeneration. Zeolites, polymeric resins, ion exchangers and granulated ferric hydroxide (GEH) were tested with different reactive dyes (M 600–1500 g mol −1). Zeolites and microporous resins were not suitable due to extremely low sorption capacities. The macroporous resins without functional groups showed moderate maximum loadings (100–400 μmol g −1 or 100–400 mg g −1) but low affinity and were not suitable for large dyes (>1000 g mol −1). loadings on anion exchangers were high but regeneration was difficult for the strong basic type (S6328a, Bayer). The weak basic type (MP62, Bayer) showed the most favorable profile: max. loadings of 200–1200 μmol g −1 (230–900 mg g −1) and complete regeneration using alkaline methanol (10% water). With GEH moderate loadings of about 150 μmol g −1 were achieved. Catalytic oxidative regeneration of GEH is possible using H 2O 2.

Purification of the Water in Spent-Fuel Holding Ponds Using Radiation-Resistant Inorganic Sorbents

A system for purifying the holding pond water for spent fuel from the first two power generating units, using radiation-resistant inorganic sorbents Termoksid, was developed and put into operation at the Beloyarsk nuclear power plant. In 26 days of operation of the purification system the radioactivity of the water in both holding ponds decreased by approximately a factor of 100. Activity amounting to 6920 Ci was removed from the two ponds and concentrated on 1 m3 of the sorbent Termoksid-3A, and 62.9 Ci remained in the pond water. Removal of spent sorbent was successfully performed by hydrotransport into a special container located directly in BV-1 under the water layer. A new batch of Termoksid-3A was loaded into the sorption filter. A second purification cycle was performed for the holding pond water. As a result, the radioactivity of the water of both ponds decreased to 2·10–6 Ci/liter, which decreases the potential danger for the service workers and the environment in the case of leakage.

Fate of Volatile Organic Compounds and Pesticides In Composted Municipal Solid Waste

Composting of municipal solid waste (MSW) has many advantages including volume reduction, reduced atmospheric emissions of methane from landfills, and the potential for beneficial use of the end product. Information about the fate of volatile organic chemicals (VOCs) which are commonly present in MSW is needed to protect the environment from undesirable emissions. To achieve this goal, the present study was undertaken to evaluate the fate of four VOCs (benzene, carbon tetrachloride, dichlorobenzene, and xylene) and two pesticides (Captan and Lindane) added to simulated MSW. Volatile organic chemicals were added at three concentrations while pesticides were tested at a single concentration. All of the treatments were replicated three times and composted in 200 L aerated static pile composters. The composters were specially equipped with pumps and flow meters to aerate the feedstock at 1.12-1.68 m3/hr, sorption filters to collect volatile organic chemicals from the exiting air stream, and leachate collection vessels. The feedstock was selected to be representative of MSW after the majority of recyclable metal and glass had been removed and was spiked with organic chemicals known to commonly occur in MSW.The results showed that the majority of VOCs present in the feedstock were lost via volatilization in the initial 48 hours of composting. Concentrations of VOCs were below detection limits after one week of composting in both the leachate and compost. Thus, while aerated pile composting is effective in removing VOCs from the feedstock, the exiting air stream will need to be monitored for approximately one week and possibly treated to meet environmental quality standards.Aerobic composting reduced the initial concentrations of 275 mg/kg each of Captan and Lindane to final concentrations of 53.8 and 158.9 mg/kg, respectively, after five weeks of composting. This corresponded to half lives of 1.5 and four weeks during composting for Captan and Lindane respectively. All concentrations of both pesticides were below detection limits in all samples of air, condensate and leachate, in dicating that none of the pesticides were volatilized and all were retained by the MSW until they biodegraded.

97/00129 The use of activated charcoal and coke in a multi-way sorption (MWS) filter for air and waste gas cleaning

The variations of thermal conductivities of solid phases versus temperature for pure Sn, pure Al and Sn–0.5 wt.% Al, Sn–2.2 wt.% Al, Sn–25 wt.% Al, Sn–50 wt.% Al, Sn–75 wt.% Al binary alloys were measured with a radial heat flow apparatus. From thermal conductivity variations versus temperature, the thermal conductivities of the solid phases at their melting temperature and temperature coefficients for same materials were also found to be 60.60 ± 0.06, 208.80 ± 0.22, 69.70 ± 0.07, 80.30 ± 0.08, 112.30 ± 0.12, 142.00 ± 0.15, 188.50 ± 0.20 W/K m and 0.00098, 0.00062, 0.00127, 0.00114, 0.00112, 0.00150, 0.00116 K−1, respectively. The thermal conductivity ratios of liquid phase to solid phase for the pure Sn, pure Al and eutectic Sn–0.5 wt.% Al alloy at their melting temperature are found to be 1.11, 1.13, 1.06 with a Bridgman type directional solidification apparatus, respectively. Thus the thermal conductivities of liquid phases for pure Sn, pure Al and eutectic Sn–0.5 wt.% Al binary alloy at their melting temperature were evaluated to be 67.26, 235.94 and 73.88 W/K m, respectively by using the values of solid phase thermal conductivities and the thermal conductivity ratios of liquid phase to solid phase.

Experimental study of 210Po release from 17Li83Pb eutectic

The release of 210Po from 17Li83Pb eutectic was experimentally investigated up to 450 °C in flows of noble gases and atmospheric air at different humidity. Aerosol and sorption filters were applied for the quantitative determination of releasing polonium aerosol and gaseous fractions. The experimental results reveal the strong dependence of 210Po release rate on temperature and the state of the eutectic surface. In the eutectic temperature range from 350 to 450 °C the polonium release rate in argon is increasing from 10 −11 to 10 −9 Ci cm −2 h −1. In all tests the 210Po activity in the carrier gas was determined in aerosol and gaseous forms. Polonium in the gaseous phase was found to be in the range from 5% to 80% of the overall concentration. The total 210Po concentration in the carrier gas near the melted eutectic surface at the temperature 450 °C reached 2.7 × 10 −10 Ci 1 −1, which exceeds the permissible level by three orders of magnitude. Comparison of experimental data with estimates based on metallic polonium evaporation indicates the formation of chemical compounds of polonium with lead and in some cases with hydroxide.

Detata-Filters for Metal Preconcentration and Multielement Determination in Natural Waters

Abstract New sorption filters containing conformationally flexible aminc-carboxylic groups were proposed for preconcentration of metals. Quantitative recovery of metals was achieved in a dynamic regime at a solution flow rate up to 4 ml.min−1.cm−2 in a pH range 3–8 from solutions with high salt content and in the presence of natural complexing agents. The dynamic capacity of DETATA-filters of the heavy metals was investigated. XRF and ICP-AES methods of heavy metals determination after preconcentration on the filters were developed.

Development and application of filters for air cleaning in nuclear power plants

The development of filter systems for air cleaning in nuclear power plants will be briefly described. The result of research work on iodine filters was the basis for the use of gasketless deep-bed filters and of the multiway sorption filter in German reactor stations. The composition of the iodine release to the environment was validated with the “discriminating iodine species sampler”. The main sources for the release of elemental iodine from BWR and PWR were discovered and finally suppressed. The mechanical strength of HEPA filters is being tested at high temperatures and humidities. Prototype HEPA filters have been developed with much higher resistance against humidity, differential pressure, and corrosion. A filter for the removal of particles during extreme operating conditions such as containment venting was developed using stainless steel fibers for the filter medium. The first filter of this type has already been built and installed in a modern German PWR as a part of the containment-venting system for serious accidents.

Identification of gas-phase dimethyl sulfate and monoethyl sulfate in the Los Angeles atmosphere

Gas-phase dimethyl sulfate and monomethyl hydrogen sulfate have been identified in the atmosphere in Los Angeles. Gas-phase concentrations of these two alkyl sulfates were determined by using analytical methods based on the collection of the compounds before collection of particles using diffusion denuders and after collection of particles using resin beds or sorption filters, and specific analysis of the collected alkyl sulfates by ion chromatography. The data show the dimethyl sulfate is present in both particles and the gas phase. The concentration of total gas-phase methyl sulfates was found to vary from 34 to 178 nmol/m/sup 3/ during the smog episode studied. These species constituted a significant fraction of the total sulfur budget in the Los Angeles basin during the sampling period.