Enhancing the Biodegradation of Polycyclic Aromatic Hydrocarbons: Effects of Nonionic Surfactant Addition on Biofilm Function and Structure

The application of surfactants for the bioremediation of sites contaminated with polycyclic aromatic hydrocarbons has been widely reported, because they are known to increase PAH solubility and desorption, thereby enhancing their bioavailability to biofilm microorganisms. The effects of a nonionic surfactant on the biodegradation of PAHs in porous media, as well as the fate of the surfactant, were investigated in this study. Column experiments in the presence of the surfactant showed that the degradation of the two-ring PAH alone was not significantly affected, but that there was a small enhancement of three- and four-ring PAH degradation when they were present as sole substrates and when using Triton X-100. This was due to the higher solubility of the PAHs in the presence of the surfactant. Biofilm seemed to respond well to binary mixtures of phenanthrene–naphthalene and pyrene–naphthalene, with removals of 45.5 and 24.1%, respectively, in the presence of the surfactant; however, higher biodegradations were always achieved by having just PAH mixtures without the surfactant, indicating the importance of cometabolic mechanisms over improved solubilization of PAHs. Optical sections taken using a confocal laser scanning microscope allowed observation of a heterogeneous web-like matrix of biofilm, with diverse biological aggregate structures.     

Rate Parameters for Methyl tert-Butyl Ether Biodegradation via a Radial Diffusion Model

A dimensionless radial diffusion model was employed to determine the first-order biodegradation rate of methyl tert-butyl ether (MTBE) by indigenous microorganisms at a laboratory scale in natural soils at different temperatures and oxygen concentrations. Variations in the biodegradation rate in response to different temperatures and oxygen concentrations were modeled by adjusting only the reaction-diffusion Thiele modulus to match the observed concentrations of the bulk fluid. The model can provide estimates for other unmeasured transport parameters such as intra-particle diffusion coefficient and mass-transfer coefficient at porous soil particle surfaces. Experimental data suggested that MTBE biodegradation follows first-order kinetics for different temperatures and oxygen concentrations. The biodegradation rate of MTBE by the microorganisms under different oxygen treatments (0–100%) ranged from 0.0015 to 0.0165 h?1. Similarly, the biodegradation rate of MTBE at different temperatures (288–303 K) ranged from 0.005 to 0.03 h?1, increasing with temperature. The rate reached its peak value at 20% oxygen concentration, and decreased substantially at higher oxygen concentrations.     

Influence of Supplemental Acetate on Bioremediation for Dissolved Polycyclic Aromatic Hydrocarbons

The influence of supplemental acetate on in situ bioremediation for the removal of dissolved polycyclic aromatic hydrocarbons (PAHs) in groundwater was evaluated in laboratory sand columns. Sand columns, inoculated with a soil enrichment culture, were fed with dissolved PAHs (9 mg/L naphthalene, 0.8 mg/L phenanthrene, 0.09 mg/L pyrene), nutrients, and hydrogen peroxide to sustain aerobic microbial growth. Pore water PAH concentration profiles were obtained during the study. Determinations of viable biomass, carbohydrate, and PAH sorption capacity were obtained at the conclusion of the experimental runs. Pore water profiles indicated that PAH biodegradation capability became more quickly established after 45 days in sand columns amended with acetate versus the unamended control. The endpoint pore water PAH concentration profiles were similar for both acetate-amended and unamended columns. Higher biomass in acetate-amended columns increased the overall sorption capacity of the sand medium for PAHs by 24–47%. Supplemental acetate resulted in minimal biofouling of the sand medium as the final hydraulic conductivity of the acetate-amended treatments was 36–72% of the clean sand value.     

Thermally Enhanced Vapor Extraction for Removing PAHs from Lampblack-Contaminated Soil

This work summarizes the results of a feasibility study in support of a soil venting-thermal desorption (SVTD) process for remediating lampblack-impacted soil. Lampblack is the solid residue resulting from the gasification of crude oil. The SVTD process couples soil vapor extraction with in situ heating. The objective of this study is to determine the required temperature for desorbing polycyclic aromatic hydrocarbons (PAHs), the compounds of regulatory concern, from lampblack. Bench-scale results are reported for the treatment of a soil-lampblack matrix containing 11 PAHs totaling about 4100 ppm (mg∕kg) total PAH (TPAH). Solids characterization analyses suggested that these PAHs constitute about 60% of the organic residue on a solid matrix dominated by fine-grained sand and carbon-based lampblack particles. Thin section imagery supports the conceptual model of hydrocarbons associated with the surface of sand grains. SVTD testing for the sand-lampblack solids indicates that temperatures in excess of about 250°C are sufficient to mobilize most of the PAHs. Specifically, at temperatures between 250°C and 300°C, the TPAH level in the soil-lampblack matrix was reduced to less than 100 ppm in 10 days. The dynamics of PAH removal were captured reasonably well by a mass balance accounting for the temperature dependent volatilization of an ideal PAH mixture. Both simulated and experimental results support the finding that the vast majority of the PAH removal from this sand-lampblack matrix was controlled by thermodynamic considerations (as opposed to mass transfer resistances). A small residual PAH fraction (roughly 40 ppm TPAH) was observed to persist in the solids even at temperatures in excess of 650°C. Although the specific state of these persistent PAHs is unknown, they may reside within an extremely nonvolatile residue or be otherwise strongly sequestered in the solid matrix.     

Chemical-Biological Treatment of Table Olive Manufacturing Wastewater

Wastewater generated in the table olive processing industries has been treated by means of an integrated wet air oxidation–aerobic biodegradation process. Chemical oxygen demand (COD) conversion in the range of 30–60% (6 h of treatment) has been achieved by using relatively mild conditions (443–483 K and 3.0–7.0 MPa of total pressure using air). Use of the homogeneous catalysts [copper (II)] or radical promoters (hydrogen peroxide) resulted in a higher efficiency of the process (roughly between 16 and 33% COD removal improvement depending on operating conditions). Biodegradability tests, conducted after the oxidation pretreatment, showed a negative effect with the addition of copper to the reaction media. Promoted experiments resulted in the highest values of biodegradability (measured as the ratio of biological oxygen demand to COD). The rate of the COD biodegradation was compared to the kinetics of the aerobic process without a previous chemical preoxidation. The calculated kinetic parameters showed the positive effect of the pretreatment (maximum growth rate of 0.03 ± 0.006 h?1 and 0.014 ± 0.00014 h?1). Acclimation of microorganisms to oxygenated species formed in a chemical preoxidation step enhanced the efficacy of the biodegradation (maximum growth rate of 0.04 ± 0.007 h?1).     

Adsorption of Polycyclic Aromatic Hydrocarbons in Aged Harbor Sediments

Polycyclic aromatic hydrocarbons (PAHs) are a group of hydrophobic organic contaminants which have low aqueous solubilities and are common pollutants in harbor sediments. Adsorption and desorption isotherms for PAHs are conducted to study the abiotic sorption of PAHs in uncontaminated harbor sediments in contact with the natural overlaying water. Representative 2-, 3-, and 4-ring PAHs are used to obtain PAH adsorption/desorption data. Linear adsorption onto sediment is obtained for the following PAHs: Naphthalene and 2-methyl naphthalene (2 ring), acenaphthene, anthracene, and phenanthrene (3 ring), and fluoranthene and pyrene (4 ring). Linear adsorption is followed by a significant hysteresis in desorption from sediment, due to strong retention by the aged sediment organic carbon. Sediment organic carbon–water partition coefficients (log?Koc) for the seven PAHs range from 2.49 to 4.63. Based on the sorption data for these representative PAHs, sediment organic carbon–water partition coefficients may be predicted for other PAH compounds, particularly the less soluble and the more hydrophobic PAHs (5 or more rings).     

An investigation into the ability of soft drinks to adhere to enamel

A mixed culture, isolated from soil contaminated with polycyclic aromatic hydrocarbons (PAHs), grew on and degraded fluoranthene in aqueous media supplemented with glucose, yeast extract, and peptone. Increased complex nitrogen levels in the medium promoted bacterial growth and a greater extent of fluoranthene degradation. Amendment of the media with high glucose levels also diminished specific fluoranthene degradation. The mixed culture was capable of degrading a range of other PAHs, including benzo[a]pyrene, anthracene, phenanthrene, acenaphthene, and fluorene. The mixed culture contained four predominant isolates, all of which were Gram-negative rods, three of which were identified as Pseudomonas putida, Flavobacterium sp., and Pseudomonas aeruginosa. Better degradation of a defined PAH mixture was observed with the mixed culture than with individual isolates. A reconstituted culture, prepared by combining the four individual isolates, manifested a similar PAH biodegradation performance to the original mixed culture. When compared with the mixed culture, individual isolates exhibited a relatively good capacity to remove more water-soluble PAHs (acenaphthene, fluorene, phenanthrene, fluoranthene). In contrast, removal of less water-soluble PAHs (anthracene and pyrene) was low or negligible with isolated cultures compared with the mixed culture.     

Biodegradation of Naphthalene-Contaminated Soils in Slurry Bioreactors

The effects of naphthalene concentrations and soil constituents (sand, clay, organic matter) on biodegrading naphthalene-contaminated soils using an acclimated Flavobacterium sp. were examined in continuously stirred slurry bioreactors. Soils with and without organic matter (1%) and kaolinite clay (20%) were used. Studies showed that sorption of naphthalene can be represented by the Freundlich isotherm. Among the soils investigated, clayey soil retarded the biodegradation process the most due to its desorption characteristics. Increasing the naphthalene contamination level from 500 mg∕kg to 25,000 mg∕kg doubled the biodegradation time in the slurry reactor with a soil loading of 10 g∕L. A pseudo first-order kinetic was observed for naphthalene biodegradation, and the biodegradation constant was determined to be 0.20 mg∕L∕h. A kinetic model was developed to simulate the biodegradation of naphthalene in a continuously stirred batch slurry reactor and to understand the role of solubilization (solid phase naphthalene), desorption, and biodegradation in the removal of naphthalene. Predictions using the numerical model agreed with the experimental data.     

Control of PAHs from Incineration by Activated Carbon Fibers

The aim of this research was to use activated carbon fibers (ACFs) to adsorb 16 polycyclic aromatic hydrocarbon (PAH) species from flue gas emissions during incineration. The operation conditions included the presence of three activated carbon fibers, the adsorption temperature (200, 300, and 340°C), and the weight of the ACFs. The removal efficiencies of the gaseous and solid-state PAHs were evaluated respectively. It was found that the BET surface area did not affect PAH removal when the BET surface area was enough for PAH removal and micropore volume was the determinant parameter for PAHs removal. The best adsorption temperature in this study was 300°C. The removal efficiency of PAHs was proportional to the weight of ACFs.     

Biodegradation of Aqueous Organic Matter over Seasonal Changes: Bioreactor Experiments with Indigenous Lake Water Bacteria

Artificial groundwater recharge for drinking water production involves infiltration of surface water through sandy soil and its capture into a groundwater aquifer. The transformation of aqueous organic matter is one of the central issues in this process. The purpose of this work was to assess the potential of indigenous microorganisms in the source water to contribute in the aqueous organic matter biodegradation. For this purpose, microorganisms were enriched from the source water in a fluidized-bed reactor (FBR) and used for kinetic studies on biodegradation of organic matter at ambient temperature range. Lake water (total organic carbon 5.8?mg?L?1) was continuously fed to the FBR containing porous carrier material to support biomass retention. In the inlet and outlet water there were on average 21±6 and 13±5×105?cells?mL?1, respectively. Biofilm accumulation (as volatile solids) reached 13.1?mg?g?1 dw carrier. In the continuous-flow mode and the batch tests, the highest oxygen consumption rate appeared in the summer, followed by the fall, spring, and winter. At low temperatures, the biodegradation of aqueous organic matter was relatively rapid initially for labile fractions followed by a slower phase for refractory fractions. The average temperature coefficient (Q10) in the system was 2.3 illustrating a strong temperature dependency of oxygen consumption. The isotopic analysis of dissolved inorganic carbon δ13CDIC analysis revealed 27 and 69% mineralizations of dissolved organic carbon at 23 and 6°C over 65 and 630 min, respectively. These results can be used to construct additional input parameters in modeling applications of artificial groundwater recharge process. The biological component especially, i.e., the biodegradation, is difficult to predict for on-site applications without experimental proof and thus the interpretation in this study will help formulate design predictions for the process.     

Developments in Biotechnology for Environmentally Benign Iron Ore Beneficiation

Biomineralization and biogenesis of iron ore deposits are illustrated in relation to indigenous microorganisms inhabiting iron ore mines. Aerobic and anaerobic microorganisms indigenous to iron oxide mineralization are analyzed. Microbially-induced flotation and flocculation of iron ore minerals such as hematite, alumina, calcite and quartz are discussed with respect to use of four types of microorganisms, namely, Paenibacillus polymyxa, Bacillus subtilis, Saccharomyces cerevisiae and Desulfovibrio desulfuricans. The role of the above organisms in the removal of silica, alumina, clays and apatite from hematite is illustrated with respect to mineral-specific bioreagents, surface chemical changes and microbe–mineral interaction mechanisms. Silica and alumina removal from real iron ores through biobeneficiation is outlined. Environmental benefits of biobeneficiation are demonstrated with respect to biodegradation of toxic reagents and environmentally-safe waste disposal and processing.     

Competitive Substrate Biodegradation during Surfactant-Enhanced Remediation

The impact of synthetic surfactants on the aqueous phase biodegradation of benzene, toluene, and p-xylene (BTpX) was studied using two anionic surfactants, sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS), and two nonionic surfactants, POE(20) sorbitan monooleate (T-maz-80) and octylphenolpoly(ethyleneoxy) ethanol (CA-620). Batch biodegradation experiments were performed to evaluate surfactant biodegradability using two different microbial cultures. Of the four surfactants used in this study, SDS and T-maz-80 were readily degraded by a microbial consortium obtained from an activated sludge treatment system, whereas only SDS was degraded by a microbial culture that was acclimated to BTpX. Biodegradation kinetic parameters associated with SDS and T-maz-80 degradation by the activated sludge consortium were estimated using respirometric data in conjunction with a nonlinear parameter estimation technique as μmax = 0.93 h?1, Ks = 96.18 mg∕L and μmax = 0.41 h?1, Ks = 31.92 mg∕L, respectively. When both BTpX and surfactant were present in the reactor along with BTpX-acclimated microorganisms, two distinct biodegradation patterns were seen. SDS was preferentially utilized inhibiting hydrocarbon biodegradation, whereas the other three surfactants had no impact on BTpX biodegradation. None of the four surfactants were toxic to the microbial cultures used in this study. Readily biodegradable surfactants are not very effective for subsurface remediation applications as they are rapidly consumed, and also because of their potential inhibitory effects on intrinsic hydrocarbon biodegradation. This greatly increases treatment costs as surfactant recovery and reuse are adversely affected.     

高效提取氧化锌烟尘中铟新工艺研究

采用中性浸出—酸性浸出—溶剂萃取工艺流程从含铟氧化锌烟尘中提铟。考察浸出温度、浸出时间、硫酸浓度、液固比对浸出效果的影响以及萃取剂浓度、萃取相比和初始酸度对铟萃取率的影响。结果表明,中性浸出除锌后再酸性浸出铟,铟浸出率高达91.6%,铟萃取率超过90%。     

Enhanced Soil Flushing for Simultaneous Removal of PAHs and Heavy Metals from Industrial Contaminated Soil

Polycyclic aromatic hydrocarbons (PAHs) and heavy metals are environmental concerns and must be removed to acceptable levels. This paper evaluates different flushing agents to enhance the remediation of soil contaminated with PAHs and heavy metals at a former manufactured gas plant site. Four flushing column tests at a constant hydraulic gradient of 1.2 were conducted using four different flushing agents, which included deionized water, chelant (0.2?M EDTA), surfactant (5% Igepal CA-720), and cyclodextrin (10% hydroxypropyl-β-cyclodextrin or HPCD). Additional column tests using Igepal and HPCD at a lower hydraulic gradient of 0.2 were conducted to investigate the effects of rate-limited desorption or solubilization of PAHs. The results showed that the EDTA produced the maximum metal removal from the soil compared with deionized water, Igepal, and HPCD under different hydraulic gradient conditions. The 0.2?M EDTA flushing solution removed approximately 25–75% of the toxic heavy metals found in the soil. None of the PAHs were removed from the soil when deionized water and EDTA were the flushing solutions. The PAHs removal efficiencies in the Igepal and HPCD systems decreased as the hydraulic gradient decreased. However, the surfactant-enhanced systems were more efficient in removing PAHs from the soil than the HPCD systems under high- and low-hydraulic gradients. The results also demonstrated that the removal of PAHs in surfactant-enhanced systems depended upon the micelles formation, whereas in the HPCD-enhanced systems, it depended upon the sterioselective diffusion of the PAHs to the nonpolar cavity of the HPCD. Overall, this study showed that the contaminant removal in soil flushing systems depends on the flushing solution affinity and selectivity toward the target contaminant and the existing hydraulic gradient condition.     

Development of a Four-Phase Remedial Scheme to Clean Up Petroleum-Hydrocarbon Contaminated Soils

In this study, a four-phase remedial scheme was developed for in situ cleanup of petroleum-hydrocarbon contaminated soils. The developed remedial scheme contained the following four phases: surfactant flushing, groundwater flushing, chemical oxidation using KMnO4 as the oxidant, and enhanced bioremediation. Laboratory bench-scale experiments were performed to evaluate the effectiveness of this developed remedial scheme on the treatment of diesel oil contaminated soils. In the surfactant and groundwater flushing batch experiment (the first and second phases), biodegradable surfactant, Simple Green (SG) (5% by weight) was applied to flush diesel oil contaminated soils with initial total petroleum-hydrocarbon (TPH) concentration of approximately 31,500??mg?kg-1. Results show that more than 90% of TPH could be removed after flushing with 40 pore volumes (PVs) of SG, followed by 25?PVs of groundwater. In the KMnO4 oxidation experiment (third phase) with initial soil TPH concentration at approximately 4,900??mg?kg-1, up to 65% of TPH removal efficiency can be obtained when 1% by weight of KMnO4 was applied for oxidation. Results also reveal that the slight increase in TPH removal was observed in experiments with SG addition (0.1% by volume) owing to increased dissolution and desorption of TPH from soils. In the enhanced bioremediation (fourth phase) batch experiments, a petroleum-hydrocarbon degrading bacterium was isolated from the soil materials after the KMnO4 oxidation experiments and identified as Pseudomonas sp. via biochemical tests and further confirmation of DNA sequencing. Results from biodegradation experiments indicate that the isolated bacterium, which survived after KMnO4 oxidation process, was capable of degrading TPH caused by diesel oils, and caused the TPH to drop from 2,105 to 487??mg?kg-1 within 15?days of incubation. The effectiveness of the four-phase remedial scheme was further confirmed by a semicontinuous batch experiment. Results from this study indicate that the four-phase scheme is a promising technology for the treatment of petroleum-hydrocarbon contaminated soils.     

萃取－旋流电积工艺从镓锗浸出液中生产阴极铜

介绍了某冶炼厂采用萃取－旋流电积工艺从镓锗浸出液中生产阴极铜的工业化应用情况。在铜的萃取生产过程中,通过优化反萃液酸度、萃取温度,同时监控浸出液中有害杂质含量和增设活性白土有机相净化装置,有效解决了铜萃取率低、分相慢和萃取有机相降解等技术问题;在铜的旋流电积生产中,采用钛基二氧化铅阳极替代钛基贵金属阳极、溶气泵加气浮澄清除油装置替换二级纤维改性材料除油装置,通过铜离子浓度电积终点准确控制、古尔胶助剂添加量、铜电积循环液温度优化,解决了阴极铜析出质量差、钛基贵金属阳极损耗大等生产难题,阴极铜的质量和阳极寿命均得到明显改善。     

Electrolytic Oxidation of Polynuclear Aromatic Hydrocarbons from Creosote Solution Using TI/IRO2 and TI/SNO2 Circular Mesh Electrodes

The electrooxidation of polynuclear aromatic hydrocarbons (PAHs) in solution was investigated. Most of the PAHs compounds are toxic and hardly biodegradable, so that a chemical or physicochemical treatment is required. In this paper, we reported treatment of synthetic creosote oily effluent (COE) containing several PAHs by using Ti/IrO2 and Ti/SnO2 circular or cylindrical mesh anode electrodes. COE was prepared with distilled water and a commercial creosote solution in the presence of an amphoteric surfactant (CAS). In addition to anode material, different operating parameters were investigated such as current density, reaction time, recycling flow rate, and oxygen injection flow rate. The first series of experiments carried out in the recirculating batch reactor showed that circular Ti/SnO2 electrode was found to be more effective in removing PAHs than circular or cylindrical Ti/IrO2 electrodes. Current density and retention time played important roles for PAHs degradation efficiency, whereas circulation flow rate and oxygen injection slightly influenced the removal efficiency. Finally, the best and simplest operating conditions (82–84% of PAHs removal) determined for PAHs degradation in COE were obtained at a current density of 15?mA/cm2 through 90 min of treatment with a recycling rate of 3.6 L/min but without O2 injection in the close loop. Likewise, in the recirculating batch tests, PAHs decomposition exhibited behaviors of the fist-order reaction with a rate coefficient (k) of 0.015?min?1. The energy consumption was 7.5?kWh/m3. The second series of experiment using successively batch and continuous treatment of COE shows that the percentage of PAHs degradation could be maintained above 80% up to 18 h of treatment, thereafter, removal efficiency decreased owing to the formation of organic substances on the electrodes surface.     

Technical note: a simplified procedure for vitamin E determination in beef muscle

A simplified method for the determination of alpha-tocopherol concentration in beef muscle was developed and evaluated. The method consists of a saponification step applied to 1-g samples of intact, fresh muscle, followed by a single isooctane extraction of the saponified samples. alpha-Tocopherol in the extract was separated by normal phase chromatography and quantified by fluorescence detection. A single extraction with the simplified method accounted for 95% of the total muscle alpha-tocopherol concentration obtained by two extractions with the Arnold et al. (J. Food Sci. 58:28, 1993) method. Recovery of added alpha-tocopherol standard after two extractions of a saponified muscle sample was 91% for the simplified method, which was not different (alpha = .78) from recovery using the Arnold method, and the efficiency of the single extraction in the simplified method was 89%. The coefficients of variation for the simplified and Arnold methods were both 3.1%. This method should permit the duplicate analysis of 100 fresh muscle samples within 24 h.     

Potential for 17β-Estradiol and Estrone Degradation in a Recharge Aquifer System

The potential for degradation of two important endocrine disrupting chemicals, 17β-estradiol (E2) and estrone (E1) in a wastewater effluent recharged aquifer system was assessed using lab scale microcosms. Biotransformation by microorganisms present in the aquifer material was found to be the major mode of removal for both organic contaminants in the microcosms. The addition of ultrafiltered secondary effluent, simulating recharge of aquifer, did not significantly alter the behavior of both E2 and E1 in the aquifer microcosms. A significant difference in E2 removal rates in microcosms that received E2 as a concentrated stock in methanol as opposed to direct dissolution of E2 into groundwater shows that the presence of methanol could alter the biodegradation kinetics of the organic pollutant of interest. The rapid utilization of methanol by indigenous methanol degraders, which was present as an alternative carbon substrate, caused rapid depletion of oxygen and, hence, development of anoxic conditions in the microcosms. Increased oxygen supply led to corresponding improved E2 biotransformation rates, indicating that E2 degradation under anoxic conditions was much slower than under aerobic conditions. On the other hand, in the presence of a high initial concentration of methanol, E1 was more persistent in the medium under aerobic conditions than under anoxic conditions. Apparently, the initial high concentration of methanol had an inhibitory effect on aerobic E1 degraders in the microcosms.     

Statistical modeling of solvent extraction equilibria: extraction of copper from sulfuric acid and ammoniacal solutions by mixtures of LIX 64N and SME 529

The statistical modeling of the equilibria in the solvent extraction of copper from sulfuric acid and ammoniacal sulfate solutions by mixtures of LIX 64N and SME 529 has been carried out. This study employed an incomplete three-level factorial design involving four variables,viz., the copper and sulfuric acid or ammonia concentrations in the aqueous phase and the concentrations of the two extractants in the organic phase. The equilibrium models showed that the active oximes in LIX 64N and SME 529 are completely compatible as regards the extraction of copper without any synergistic effects between the reagents being observed. The percentage of copper extracted increases with increased extractant concentration in the organic phase, but is affected adversely by increased sulfuric acid and copper sulfate concentrations in the aqueous phase. As expected, the equilibrium extraction of copper is influenced by the diluent, with higher copper extractions being attained with mixtures of LIX 64N and SME 529 in MSB-210 as compared with Escaid 100, a diluent having a higher aromatic content and giving rise to a lower degree of oxime aggregation. The copper loading efficiency of the reagents is high for extractions from ammoniacal solution — 86.6 pct and 89.4 pct copper in the diluents MSB-210 and Escaid 100, respectively, at the center points of the experimental designvs 47.0 pct and 43.3 pct in the case of sulfuric acid solution extractions. Copper loading efficiencies greater than 100 pct are attainable in ammoniacal media, particularly in situations where the aqueous copper concentration is greatly in excess of the combined extradant concentration. This overloading is attributable to the uptake of ammonia by the hydroxyoximes and can be expected to increase with increasing aromatic content of the diluent, as in the case of Escaid 100, as a result of decreased oxime aggregation.