The application of nanoemulsions with different orange oil concentrations to remediate crude oil-contaminated soil

The petroleum industry stands out for causing significant environmental risks from contamination of the air, water and soil. The removal of organic pollutants from the environment poses a great technological challenge, making it increasingly necessary to develop efficient clean-up technologies. Surfactant solutions have been used to remediate soils and aquifers contaminated by hydrocarbons or crude oil derivatives. The aim of this study was to develop nanoemulsions and analyze their efficiency in extracting crude oil from a sand sample. The nanoemulsions were prepared by the phase inversion temperature (PIT) method. The oil phase consisted of orange oil and the nonionic surfactant ethoxylated lauryl ether (Ultrol L70) was used to stabilize the nanoemulsions. The surfactant concentrations were varied from 10 to 12 wt% and the oil phase from 5 to 20 wt%. The efficiency of extraction of oil from sand was assessed using the two nanoemulsions that presented the greatest stability (containing 5 wt% oil phase with 12 wt% surfactant and 20 wt% oil phase with 10 wt% surfactant). A 2(3) factorial experimental design with center point was used to evaluate and improve the soil washing process, varying the time, temperature and agitation speed of the system. The highest efficiencies were obtained at 45 degrees C.     

Decontamination of uranium-contaminated waste oil using supercritical fluid and nitric acid

The waste oil used in nuclear fuel processing is contaminated with uranium because of its contact with materials or environments containing uranium. Under current law, waste oil that has been contaminated with uranium is very difficult to dispose of at a radioactive waste disposal site. To dispose of the uranium-contaminated waste oil, the uranium was separated from the contaminated waste oil. Supercritical R-22 is an excellent solvent for extracting clean oil from uranium-contaminated waste oil. The critical temperature of R-22 is 96.15 °C and the critical pressure is 49.9 bar. In this study, a process to remove uranium from the uranium-contaminated waste oil using supercritical R-22 was developed. The waste oil has a small amount of additives containing N, S or P, such as amines, dithiocarbamates and dialkyldithiophosphates. It seems that these organic additives form uranium-combined compounds. For this reason, dissolution of uranium from the uranium-combined compounds using nitric acid was needed. The efficiency of the removal of uranium from the uranium-contaminated waste oil using supercritical R-22 extraction and nitric acid treatment was determined.     

Heavy metal removal from sediments by biosurfactants.

Batch washing experiments were used to evaluate the feasibility of using biosurfactants for the removal of heavy metals from sediments. Surfactin from Bacillus subtilis, rhamnolipids from Pseudomonas aeruginosa and sophorolipid from Torulopsis bombicola were evaluated using a metal-contaminated sediment (110mg/kg copper and 3300mg/kg zinc). A single washing with 0.5% rhamnolipid removed 65% of the copper and 18% of the zinc, whereas 4% sophorolipid removed 25% of the copper and 60% of the zinc. Surfactin was less effective, removing 15% of the copper and 6% of the zinc. The technique of ultrafiltration and zeta potential measurements were used to determine the mechanism of metal removal by the surfactants. It was then postulated that metal removal by the biosurfactants occurs through sorption of the surfactant on to the soil surface and complexation with the metal, detachment of the metal from the soil into the soil solution and hence association with surfactant micelles. Sequential extraction procedures were used on the sediment to determine the speciation of the heavy metals before and after surfactant washing. The carbonate and oxide fractions accounted for over 90% of the zinc present in the sediments. The organic fraction constituted over 70% of the copper. Sequential extraction of the sediments after washing with the various surfactants indicated that the biosurfactants, rhamnolipid and surfactin could remove the organically-bound copper and that the sophorolipid could remove the carbonate and oxide-bound zinc. Therefore, heavy metal removal from sediments is feasible and further research will be conducted.     

Removal of chromium (VI) from aqueous solution using treated oil palm fibre

This study proposed an oil palm by-product as a low-cost adsorbent for the removal of hexavalent chromium [Cr (VI)] from aqueous solution. Adsorption of Cr (VI) by sulphuric acid and heat-treated oil palm fibre was conducted using batch tests. The influence of pH, contact time, initial chromium concentration and adsorbent dosage on the removal of Cr (VI) from the solutions was investigated. The optimum initial pH for maximum uptake of Cr (VI) from aqueous solution was found to be 1.5. The removal efficiency was found to correlate with the initial Cr (VI) concentration, adsorbent dosage as well as the contact time between Cr (VI) and the adsorbent. The adsorption kinetics tested with pseudo first order and pseudo second order models yielded high R(2) values from 0.9254 to 0.9870 and from 0.9936 to 0.9998, respectively. The analysis of variance (ANOVA) showed significant difference between the R(2) values of the two models at 99% confidence level. The Freundlich isotherm (R(2)=0.8778) described Cr (VI) adsorption slightly better than the Langmuir isotherm (R(2)=0.8715). Difficulty in desorption of Cr (VI) suggests the suitability of treated oil palm fibre as a single-use adsorbent for Cr (VI) removal from aqueous solution.     

Copper leaching from a sandy soil: mechanism and parameters affecting EDTA extraction

A series of 24h batch tests of copper extraction from a sandy soil were performed by washing the soil with aqueous solution of ethylenediaminetetraacetic acid, EDTA. EDTA versus copper molar ratio were in the range between 1 (equimolar tests) and 13.3. The tests were performed at three selected liquid/solid ratio, 5, 12.5 and 25. Results show that decreasing the pH of the washing solution an higher copper extraction yield was achieved: an almost complete copper extraction was achieved after 23 h of mixing at a L/S = 5, and after 5 h of mixing at an L/S = 12.5. The mechanism of copper extraction was found to involve two sequential processes: the former dissolution of metal salts, that lead to an initial high concentration of both copper and some competitive cations (essentially Ca(2+)), and the following EDTA exchange reaction between calcium and copper complexes, which corresponded an increase of pH in the washing solution. A negligible extraction of Fe(3+) was also observed at the investigated operative conditions.     

Biosorption performance,combustion behavior,and leaching characteristics of olive solid waste during the removal of copper and nickel from aqueous solutions

Several researchers have proved that agricultural by-products constitute good adsorbents for removing heavy metals from aqueous solution. However, few investigations have identified efficient strategies for the adsorbent′s regeneration. Hence, a global methodology for the removal of copper and nickel metals from wastewater including metal biosorption, thermal treatment and residual ash landfill is proposed. In order to validate this strategy, olive solid waste (OSW), provided by an olive oil mill from Tunisia, were used to remove copper and nickel on batch experiments. Copper and nickel were adsorbed on a monolayer of OSW surface with maximal adsorption capacity (q _max) of 3.6 and 1.7 mg g^?1, respectively. Contaminated OSW with copper and nickel were combusted at 850 °C in an electrical furnace. About 96 % of each metal was recovered in residual ashes that present a good secondary raw material for copper and nickel production. Low leaching transfers (≤4 %) were observed for copper and nickel from residual ashes leading to the possibility to be landfilled. Therefore, the suggested process can be used as an alternative to the classical technologies for effluent decontamination.     

The effect of ionic strength and hardness of water on the non-ionic surfactant-enhanced remediation of perchloroethylene contamination

The objective of this study is to evaluate the perchloroethylene (PCE) removal by an aqueous surfactant solutions based on influential factors (ionic strength, hardness) of various groundwaters and surface waters contaminated with PCE. The experimental methods used in this study were separatory funnel experiments and batch experiments. Separatory funnel experiments were performed to determine which surfactants are good solubilizers for PCE. Batch experiments were performed to evaluate the effect of ions in sampled water for PCE removal. The results of separatory funnel experiments indicated that the surfactant polyoxyethylene (20) sorbitan monostearate (Tween 60) showed to be a predominant solubilizer for the removal of PCE (87.3%). Separatory funnel experiments also showed that the hydrophilic-lipophilic balance (HLB) number and the chemical structure of the surfactants were good indicators of surfactant effectiveness for removal of PCE from water. The results of batch experiments showed that non-ionic surfactants are affected by the ionic strength of sampled water. The % of PCE removal of the Tween 60 surfactant solution was measured to be 88.3% by batch experiments. This result was affected by the characteristics of the surfactant (HLB, chemical structures) and the ionic strength of water. Therefore, the ionic strength of contaminated water, HLB and chemical structures of surfactants must be considered in surfactant-enhanced remediation.     

Clean operations in the tanning industry: aqueous degreasing coupled to ultrafiltration

 A process of aqueous degreasing is proposed, avoiding the use of organic solvents, in order to reduce fat substances present in sheepskins. Efficiency of the new process was increased coupling the degreasing to a pressure-driven membrane operation such as ultrafiltration. Increasing ultrafiltration time from 200 to 300 minutes yielded an increase of fats removal from 46% to 55% of the initial content. At 52  °C, the permeate flux decreased only 12.7% in 300 minutes. Recycling the permeate, that is the aqueous surfactant solution, permitted to save fresh water significantly compared to the open-washing system. Studies of membrane cleaning, using an enzymatic washing solution, showed a restore of the initial flux. A theoretical analysis was developed to decribe the behaviour of the mentioned system. Received: 11 February 1999 / Accepted: 12 May 1999     

Magnetically Modified Waste Bark of Aegle marmelos Tree as a Promising Biosorbent for Uranium(VI) Sorption

Radiochemistry - Magnetically modified waste bark of the Aegle marmelos tree was prepared by using green synthesis method and was used in a batch system for U(VI) removal from aqueous solution. The...     

超声强化超临界二氧化碳除锈除油污

结合超声清洗的优势与超临界二氧化碳的特性,设计出超声强化超临界二氧化碳复合清洗实验平台,超声换能器最大发射声功率为1 200 W,换能器每工作10 s停止20 s,即一个工作周期为30 s。利用实验平台开展了CD03钢片表面除锈实验,使用ZEISSMerlin高分辨率热场发射扫描电镜对CD03钢片表面进行扫描电子显微镜(Scanning Electronic Microscopy, SEM)和能谱(Energy Dispersive Spectrometer, EDS)分析,实验结果表明,随着清洗时间的延长,铁锈在超声作用下逐渐剥落,超声作用适当的工作周期数后,清洗效果达到最佳,超声作用时间太长会造成对钢片基体的损伤。利用实验平台开展了碳钢片表面油污清除实验,使用徕卡光学显微镜对清洗后的碳钢片做表面形貌观察,利用JA2003电子天平等手段对清洗效果进行了计算分析,同样,超声强化超临界二氧化碳油污清洗也存在一个最佳清洗时间。但是,不同污染所需的最佳清洗时间不同,甚至可以相差很大。在实际的清洗中要先根据污染物的类别确定最佳清洗时间,然后进行清洗。     

超声清洗法回收冷轧厂磁过滤物中的纳米铁粉

研究一种冷轧厂磁过滤物中纳米铁粉的回收方法,采用超声清洗法除去铁粉表面的油污,得到纯净的纳米铁粉,通过试验研究超声频率、功率密度、清洗温度对除油效果的影响,采用X射线衍射和扫描电子显微镜对铁粉产品进行表征。结果表明,相对于机械搅拌清洗,采用超声清洗含油铁粉,可提高清洗液的除油能力;超声频率为40 kHz,功率密度为0.44 W/cm2,清洗温度为40℃时,用清洗液清洗4次,每次清洗时间为20 min,用去离子水漂洗至澄清,真空干燥5 h,所得纳米铁粉中铁元素的质量分数为95.75%。     

Electrodialytic removal of heavy metals from municipal solid waste incineration fly ash using ammonium citrate as assisting agent

Electrodialytic remediation, an electrochemically assisted separation method, has previously shown potential for removal of heavy metals from municipal solid waste incineration (MSWI) fly ashes. In this work electrodialytic remediation of MSWI fly ash using ammonium citrate as assisting agent was studied, and the results were compared with traditional batch extraction experiments. The application of electric current was found to increase the heavy metal release significantly compared to batch extraction experiments at comparable conditions (same liquid-to-solid ratio, same assisting agent, and same extraction time). Up to 86% Cd, 20% Pb, 62% Zn, 81% Cu and 44% Cr was removed from 75 g of MSWI fly ash in electrodialytic remediation experiments using ammonium citrate as assisting agent. The time range for the experiments varied between 5 and 70 days.     

Removal of basic dye from aqueous medium using a novel agricultural waste material: pumpkin seed hull

In this work, pumpkin seed hull (PSH), an agricultural solid waste, is proposed as a novel material for the removal of methylene blue (MB) from aqueous solutions. The effects of the initial concentration, agitation time and solution pH were studied in batch experiments at 30 degrees C. The equilibrium process was described well by the multilayer adsorption isotherm. The adsorption kinetics can be predicted by the pseudo-first-order and the modified pseudo-first-order models. The mechanism of adsorption was also studied. It was found that for a short time period the rate of adsorption is controlled by film diffusion. However, at longer adsorption times, pore-diffusion controls the rate of adsorption. Pore diffusion takes place in two distinct regimes, corresponding to diffusion in macro- and mesopores. The results demonstrate that the PSH is very effective in the removal of MB from aqueous solutions.     

Selective removal of cesium from Acid solutions with immobilized copper ferrocyanide

Copper ferrocyanide can be immobilized on Chelex-20, a technical grade chelating resin, for selective removal of cesium from neutral to acidic solutions. The immobilized copper ferrocyanide is much easier to handle than the copper ferrocyanide powder in extraction and separation of cesium from aqueous solutions. In the presence of a reducing agent such as hydrazine, the immobilized copper ferrocyanide resin is able to remove 98% of the cesium from a simulated acid waste solution in one cycle of batch experiments. The resin shows promising properties for remediation of acidic nuclear wastes and for concentration of (137)Cs from environmental samples for quantitative analysis.     

Adsorption characteristics of trivalent chromium on palm oil fuel ash

The metal uptake characteristics of ash particles obtained from the combustion of oil palm solid waste (referred to as palm oil fuel ash) are evaluated using trivalent chromium as a model adsorbate. The equilibrium and kinetic properties of Cr(III) are studied in batch stirred-tank experiments. The extent of Cr(III) removal increases with an increase in solution pH. The maximum equilibrium uptake capacity at pH 6 is 0.31 mmol/g of sorbent. A Langmuir isotherm model with pH-dependent parameters accounts very well for the measured equilibrium data. Modeling studies using a second order irreversible reaction model and a pseudo-first order kinetic model indicate that transient profiles obtained experimentally for a range of initial metal concentrations and sorbent dosages are in good agreement with calculated curves of both models. The two kinetic models can be employed for a useful summary of the experimental data so long as their rate coefficients are empirically correlated with the two system variables: initial metal concentration and sorbent dosage. Electronic Publication     

Characterisation and classification of solid wastes coming from reductive acid leaching of low-grade manganiferous ore

The present work was focused on the acid leaching process for manganese extraction in reducing environment to low-grade manganiferous ore that comes from Central Italy. The aim of this study was to establish optimum leaching operating conditions to reduce treatment costs of waste or, even better, to allow a waste valorisation as raw materials for other applications. Consequently, the main focus of the work was the characterization and classification of the solid wastes coming from the process carried out at different operating conditions; at the same moment the effect of process parameters on Mn extraction was also analysed. The effect of particles size on the manganese extraction in reductive acid leaching process was investigated, by using lactose as reducing agent. Particle size did not show a large influence on the Mn extraction yields in the investigated process conditions. This aspect suggests the use of the leaching waste for civil and/or environmental application: use of leaching solid wastes like filling material is to be applied, for example, for environmental restoration. The classification of the solid wastes, according to the Italian Laws about Release Test (RT), has demonstrated that the solid waste produced by leaching can be classifiable as "hazardous special waste". An improvement of solid washing let to reduce the SO(4)(2-) and an appropriate treatment is necessary to reduce the dangerousness of these solids. Possible application of ore and waste as raw materials in the ceramic industry was demonstrated not to be feasible.     

Adsorption of herbicide paraquat by clay mineral regenerated from spent bleaching earth

The adsorption of herbicide paraquat (as model adsorbate) in aqueous solution onto regenerated clay mineral from bleaching earth waste has been studied in a batch reaction system. The adsorption rate has been investigated under the controlled process parameters including initial pH, salinity and temperature. Based on the high affinity between cationic paraquat and clay mineral, a pseudo-second order model has been developed using experimental data to predict the rate constant of adsorption, and equilibrium adsorption capacity. The results showed that the adsorption process could be satisfactorily described with the reaction model and were reasonably explained by assuming a competitive adsorption mechanism in the ion exchange process. Further, the fitted adsorption capacity at equilibrium decreased with increasing temperature. It implied that the strong interaction might play an important role in the paraquat-clay system. Overall, the results from this study demonstrated that the clay resource regenerated from bleaching earth waste could be used as a low-cost mineral adsorbent for the removal of environmental cationic organic pollutants from the aqueous solution.     

Adsorption of phenol and p-chlorophenol from their single and bisolute aqueous solutions on Amberlite XAD-16 resin

Removal of phenol and p-chlorophenol from synthetic single and bisolute aqueous solutions at 303.15 K through adsorption on Amberlite XAD-16 resin under batch equilibrium and dynamic column experimental conditions was investigated. The equilibrium adsorption data from single component solutions were fitted to Langmuir and Freundlich adsorption isotherm models to evaluate the model parameters and the parameters in turn were used to predict the extent of adsorption from bisolute aqueous solutions using Ideal Solution Adsorption (IAS) model. The effect of pH on removal of phenol and p-chlorophenol from single and bisolute systems was studied. The breakthrough capacity and total capacity of the resin for the adsorbates at different concentrations were evaluated through column adsorption studies. Attempts were made to regenerate the resin by solvent washing using methanol as an eluent. The limited number of adsorption-desorption cycles indicated that the adsorption capacity of the resin remained unchanged.     

某产品零件成品热处理表面质量研究与应用

目的研究某产品在热处理后,表面存在的附着物对后续磷化膜质量的影响。方法将原热处理工艺中采用的三碱清洗剂更换为除油效果更好的MT-29清洗剂,用碱水清洗后,将一次热水洗改为连续两次热水洗,确保零件表面无异物。结果工艺改进前,磷化后的零件80%以上存在起皮现象,需要反复打磨,工艺改进之后,一次磷化通过率达到了100%,电泳涂漆质量满足产品要求。结论对成品热处理零件,三碱清洗剂对淬火油的清洗效果不佳,应采用专用的除油清洗剂;热水洗对成品热处理零件表面质量有一定的影响。     

Mathematical evaluation of activated carbon adsorption for surfactant recovery in a soil washing process

The performances of various soil washing processes, including surfactant recovery by selective adsorption, were evaluated using a mathematical model for partitioning a target compound and surfactant in water/sorbent system. Phenanthrene was selected as a representative hazardous organic compound and Triton X-100 as a surfactant. Two activated carbons that differed in size (Darco 20-40 mesh and >100 mesh sizes) were used in adsorption experiments. The adsorption isotherms of the chemicals were used in model simulations for various washing scenarios. The optimal process conditions were suggested to minimize the dosage of activated carbon and surfactant and the number of washings. We estimated that the requirement of surfactant could be reduced to 33% of surfactant requirements (from 265 to 86.6g) with a reuse step using 9.1g activated carbon (>100 mesh) to achieve 90% removal of phenanthrene (initially 100mg kg-soil(-1)) with a water/soil ratio of 10.