Copper removal from an industrial waste by bioleaching

Summary Copper contained in a solid industrial waste produced in a silicone manufacturing process was leached with spent iron medium from aThiobacillus ferrooxidans culture. Most effective leaching was observed in a continuously fed, dual reactor system. Spent iron medium was generated by growingT. ferrooxidans in 0.9 K iron medium at pH 1.5 in the first reactor, and was transferred to a second reactor in which it leached the copper from the waste. Leaching was effective at a pulp density of the waste material as high as 20%. In experiments run at a pulp density of 2.5%, the spent iron medium was most efficient in leaching copper when it was first diluted 100-fold with a mineral salts solution at pH 1.5. Removal of the copper from the waste appeared to involve its displacement by acid, dissolved mineral salts, and ferric iron. Potentials for practical application of this process are discussed.     

Effects of snow removal and algal photoacclimation on growth and export of ice algae

Net growth of ice algae in response to changes in overlying snow cover was studied after manipulating snow thickness on land-fast, Arctic sea ice. Parallel laboratory experiments measured the effect of changing irradiance on growth rate of the ice diatom, Nitzschia frigida. After complete removal of thick snow (≥9 cm), in situ ice algae biomass declined (over 7–12 days), while removal of thin snow layers (4–5 cm), or partial snow removal, increased net algal growth. Ice bottom ablation sometimes followed snow removal, but did not always result in net loss of algae. Similarly, in laboratory experiments, small increases in irradiance increased algal growth rate, while greater light shifts suppressed growth for 3–6 days. However, N. frigida could acclimate to relatively high irradiance (110 μmol photons m² s⁻¹). The results suggest that algal loss following removal of a thick snow layer was due to the combination of photoinhibition and bottom ablation. The smaller relative increase in irradiance after removal of thin or partial snow layers allowed algae to maintain high specific-growth rates that compensated for loss from physical mechanisms. Thus, the response of ice algae to snow loss depends both on the amount of change in snow depth and algal photophysiology. The complex response of ice algae growth and export loss to frequently changing snow fields may contribute to horizontal and temporal patchiness of ecologically and biogeochemically important variables in sea ice and should be considered in predictions of how climate change will affect Arctic marine ecosystems.     

Remote detection of algae by copepods: responses to algal size, odors and motility

Selective feeding on large algae by copepods involves remotedetection of individual particles and subsequent active captureresponses In this study we use radiotracer experiments to quantifythe clearance rates of five coexisting freshwater copepods andto investigate the relative merits of the chemoreception andmechanoreception hypotheses of remote detection Tropocyclopsand three diaptomid copepods exhibited relatively high clearancerates when feeding on low concentrations of large algae, suggestingthat most previous studies with freshwater copepods have underestimatedmaximal clearance rates and the degree of size selectivity.All five species of copepods exihibited strong selection foran intermediate-sized flagellate (25 µm Cartena) or alarge-sized nonmotile alga (80 µ.m Pediastrum) over asmall-sized flagellate (6 µ.m Chlamydomonas). The weight-specificclearance rate for Tropocylops prasmus feeding on motile Cartena(271 ml mg^–1 h^–1) was about twice that of threediaptomid copepods and more than an order-of-magnitude higherthan the estimate for Epischura lacustris feeding on its preferredalga, Pediastrum Assuming that distance chemoreception (‘smell’)is important in remote detection, we predicted that the additionof high concentrations of ‘algal odors’ would obscureany chemical gradients emanating from individual algal cellsand would thereby hinder the remote detection and active captureof large algae Contrary to this hypothesis, the addition ofamino acids, sucrose, and algal extracts had no effect on theclearance rates and selectivity of Diaptomus birgei. These results,together with recent cinematographic studies (Vanderploeg etal.,1990), suggest that mechanoreception is the primary mechanismfor the remote detection of large particles by diaptomid copepods.A raptorial cyclopoid, Tropocyclops prasinus, exhibited strongpreferences for motile algae, whereas a suspension-feeding calanoid,D birgei, did not select between motile and nonmotile cells.Motility appears to be an important factor in algal detectionfor small cyclopoid copepods but not for suspension-feedingdiaptomids     

Pectin-rich fruit wastes as biosorbents for heavy metal removal: equilibrium and kinetics

Biosorption can be used as a cost effective and efficient technique for the removal of toxic heavy metals from wastewater. Waste materials from industries such as food processing and agriculture may act as biosorbents. This study investigates the removal of cadmium by fruit wastes (derived from several citrus fruits, apples and grapes). Citrus peels were identified as the most promising biosorbent due to high metal uptake in conjunction with physical stability. Uptake was rapid with equilibrium reached after 30-80 min depending on the particle size (0.18-0.9 mm). Sorption kinetics followed a second-order model. Sorption equilibrium isotherms could be described by the Langmuir model in some cases, whereas in others an S-shaped isotherm was observed, that did not follow the Langmuir isotherm model. The metal uptake increased with pH, with uptake capacities ranging between 0.5 and 0.9 meq/g of dry peel. Due to their low cost, good uptake capacity, and rapid kinetics, citrus peels are a promising biosorbent material warranting further study.     

Equilibrium and kinetics studies of heavy metal ions biosorption on green algae waste biomass

The biosorption of Pb(II), Cd(II), and Co(II), respectively, from aqueous solution on green algae waste biomass was investigated. The green algae waste biomass was obtained from marine green algae after extraction of oil, and was used as low-cost biosorbent. Batch shaking experiments were performed to examine the effects of initial solution pH, contact time and temperature. The equilibrium biosorption data were analyzed using two isotherm models (Langmuir and Freundlich) and two kinetics models (pseudo-first order and pseudo-second order). The results indicate that Langmuir model provide best correlation of experimental data, and the pseudo-second order kinetic equation could best describe the biosorption kinetics of considered heavy metals.     

Permian algae and algal microfacies from unayzah,quassim district,saudi arabia

Summary Late Permian bioclastic calcarenite beds of the middle Khuff Formation were sampled for their algal constituents near the city of Unayzah, Quassim district in central Saudia Arabia. The algal flora includes two species of udoteacean algae (Succodium difficile andSuccodium sp.), the dasycladacean algaMizzia velebitana and two species of red algae (Gymnocodium bellerophontis, Permocalculus plumosus). Other algal floral remains found forming isolated single layers which have generally been named algal microfacies. These include a phylloid microfacies, an oncoid microfacies and algal stromatolites. The Khuff Formation is well-known for its accumulation of non-associated gas and particularly for its oil accumulation in eastern Saudi Arabia and the Arabian Gulf states.     

Degradation of urea by bacteria and algae in mass algal cultures.

Studies were conducted to determine the role of bacteria and algae in the degradation of urea in industrial waste waters. The microflora accompanying algae in continuous cultures on waste waters from the nitrogen fertilizers industry was found to include bacteria capable of intensive degradation of urea. Urea hydrolyzing bacteria are with time eliminated from the algal culture. This elimination can be attributed to algal metabolites which inhibit the development of sensitive bacteria. The Chlorella vulgaris strain used in the treatment of wast waters from the nitrogen fertilizers industry did not hydrolyse urea.     

Colour and AOX removal from pulping effluents by algae

A mixed culture of algae was used to treat pulping mill effluent in terms of removing both colour and adsorbably organic halides (AOX). The removal of AOX from pulping effluent increased with increasing initial colour value of the effluent. However, for the total mill effluent (composed of both pulping and bleaching effluents), AOX removal was found to be independent of initial colour value, and was around 70%. Up to 80% removal of colour from pulping effluent was achieved within 30 days under continuous lighting conditions. It was found that algae reduced the colour of pulping effluent of relatively low initial colour more efficiently than that of high initial colour. Under simulated field lighting conditions, up to 60% colour removal from pulping effluent was observed after 60 days of exposure, whereas for the total mill effluent it was up to 64% after 45 days. Total organic carbon and lignin (UVA₂₈₀) were also removed to a significant extent, suggesting that the mechanism of colour removal might not be transformation of the coloured lignin molecules to non-coloured ones. Analysis of alkaline extraction of the algal biomass and material balance findings indicated that the main colour removal mechanism was metabolism rather than adsorption. The experimental results were also analysed using multiple regression techniques and a mathematical model was developed to express the removal of colour from pulping effluents in terms of initial colour value, exposure time and lighting periods as well as interactions between these variables. Received: 12 January 1999 / Revision received: 25 March 1999 / Accepted: 26 March 1999     

Copper adsorption kinetics of cultured algal cells and freshwater phytoplankton with emphasis on cell surface characteristics

Comparative studies were carried out on the adsorption of copper by a range of laboratory-cultured algae and freshwater phytoplankton samples. The level of surface mucilage associated with the cultured algae ranged from high (Anabaena spiroides, Eudorina elegans) to moderate (Anabaena cylindrica, Microcystis aeruginosa) to complete absence (Chlorella vulgaris, Asterionella formosa, Aulacoseira varians, Ceratium hirundinella). With laboratory cultures, the rapid uptake, EDTA release and quantitative similarity between living and dead (glutaraldehyde-fixed) algae were consistent with physical binding of Cu at the cell surface. The higher Cu adsorption per unit surface area and longer adsorption time of mucilaginous algae in the time-course study, and the relatively high level of Cu bound to mucilage found by X-ray microanalysis suggest that mucilage played an important role in metal binding. For all species examined, Cu adsorption kinetics (external Cu concentrations 1 to 1000 mg L⁻¹) showed a clear fit to the Freundlich, but not the Langmuir isotherm, indicating a monolayer adsorption model with heterogenous binding sites. The Freundlich adsorption capacity constant (K_f) was higher in mucilaginous (3.96–12.62) compared to nonmucilaginous (0.36–3.63) species, but binding intensity (Freundlich constant 1/n) did not differ between the two cell types. The results suggest that mucilaginous algal species may have potential as biosorbents for treatment of industrial effluents containing heavy metals. Investigation of the Cu adsorption behavior of four mixed phytoplankton samples also revealed a good fit to the Freundlich, but not the Langmuir, isotherm. Freundlich constants were in the range 2.3–3.2 for samples dominated by Chlorophyta, Bacillariophyta and Cyanophyta, but recorded a value of 7.4 in the sample dominated by Dinophyta. Comparison with data from laboratory monocultures suggested that the adsorption kinetics of mixed environmental phytoplankton samples cannot be predicted simply in terms of the major algal species.     

The reactive extraction of phenylalanine with Aliquat 336: buffer co-extraction equilibrium and mass transfer kinetics

The occurrence of significant co-extraction of buffer anions by the ion exchanger Aliquat 336 is unavoidable when high levels of system buffering is required. The co-extraction will result in inaccurate equilibrium and mass-transfer characterization of such a system unless its occurrence is taken into account, making process design and control difficult. A study of the equilibrium of phenylalanine extraction using Aliquat 336, a system where high levels of hydroxyl co-extraction occurs, was used as a model case to develop a method of accounting for co-extraction in mass-transfer modeling. Analysis of the equilibrium between bulk-aqueous-phase chloride and phenylalanine concentrations during mass transfer in a stirred-transfer cell showed there to be linear equilibrium relationships between the two parameters for a given extraction system of the form C(Cl,t) = alpha(C(A,t) - C(A,0)) for forward extraction and C(Cl,t) = epsilon C(A,t) + C(Cl,0) for backward extraction. The constants of proportionality of these relationships, or the "co-extraction constants," alpha and epsilon, were shown to be related to the selectivity of Aliquat 336 for the phenylalanine anion by the relationships alpha = -(1/S + 1) and epsilon; = -(1/S(-1) + 1). The linear equilibrium relationships were used to develop two-film theory mass-transfer models for both forward and backward extraction that account for co-extraction. These showed much higher accuracy in modeling stirred-transfer-cell data than the equivalent models which ignored co-extraction.     

A sustainable process for adsorptive removal of methylene blue onto a food grade mucilage: kinetics,thermodynamics, and equilibrium evaluation

Abstract

Adsorption of dyes onto natural materials like polysaccharides is considered a green chemistry approach for remediation of wastewater. In this work, the polysaccharide isolated from the corm of Colocasia esculenta (L.) Schott or taro tuber (CEM) was utilized for removing methylene blue (MB) from aqueous solution by batch adsorption method. The CEM adsorbent was characterized by FTIR spectroscopy, Brunauer–Emmett–Teller (BET), and scanning electron microscopy (SEM). The solution pH and adsorbent dose have been found to have a significant positive correlation with the adsorptive removal efficiency of CEM for MB dye. The removal efficiency of CEM was found to be 72.35% under the optimum conditions; 20?mg/L initial concentration of dye, 120?mg of adsorbent dose, solution pH 8.5, 311.2?K temperature and 80?min contact time. The adsorption of MB onto CEM followed best the Freundlich isotherm and pseudo-second-order kinetics. The adsorption was thermodynamically favorable and was endothermic in nature. The desorption/adsorption data justifiably indicated the reuse capability of CEM adsorbent for MB adsorption. Hence, CEM may be regarded as an eco-friendly and cost-effective natural adsorbent for MB dye removal from aqueous solution.     

The effect of phosphate concentration on growth and agar content of Gelidium robustum (Gelidiaceae,Rhodophyta) in culture

Phosphate concentration of the growth medium was found to affect the growth rate and agar yield of a clone of Gelidium robustum grown in the laboratory. To study differences in growth we used phosphate concentrations from 0 to 200 µM. To determine the effect of phosphate on agar yield and its properties we used concentrations from 0 to 20 µM. Growth rates generally increased with increasing phosphate concentration, with the highest growth rate (21% d^–1) obtained at 150 µM. Agar yield as percentage of fresh weight was highest (10%) in the algae grown with low phosphate concentrations, but agar yield as percentage of dry weight was highest(43%) at 20 µM of phosphate. Gel strength increased with phosphate concentration with a maximum of 160 g m^–2 for 0.75% gels for the cultures at 20 µM. Melting and gelling temperatures of the gels were also affected by phosphate concentration of the growth medium. Starch yield was highest in algae grown in low phosphate concentrations.     

Treatment of dairy manure effluent using freshwater algae: algal productivity and recovery of manure nutrients using pilot-scale algal turf scrubbers

Cultivating algae on nitrogen (N) and phosphorus (P) in animal manure effluents presents an alternative to the current practice of land application. The objective of this study was to determine values for productivity, nutrient content, and nutrient recovery using filamentous green algae grown in outdoor raceways at different loading rates of raw and anaerobically digested dairy manure effluent. Algal turf scrubber raceways (30m(2) each) were operated in central Maryland for approximately 270 days each year (roughly April 1-December 31) from 2003 to 2006. Algal biomass was harvested every 4-12 days from the raceways after daily additions of manure effluent corresponding to loading rates of 0.3 to 2.5g total N (TN) and 0.08 to 0.42g total P (TP) m(-2)d(-1). Mean algal productivity values increased from approximately 2.5g DW m(-2)d(-1) at the lowest loading rate (0.3g TN m(-2)d(-1)) to 25g DW m(-2)d(-1) at the highest loading rate (2.5g TN m(-2)d(-1)). Mean N and P contents in the dried biomass increased 1.5-2.0-fold with increasing loading rate up to maximums of 7% N and 1% P (dry weight basis). Although variable, algal N and P accounted for roughly 70-90% of input N and P at loading rates below 1g TN, 0.15g TP m(-2)d(-1). N and P recovery rates decreased to 50-80% at higher loading rates. There were no significant differences in algal productivity, algal N and P content, or N and P recovery values from raceways with carbon dioxide supplementation compared to values from raceways without added carbon dioxide. Projected annual operational costs are very high on a per animal basis ($780 per cow). However, within the context of reducing nutrient inputs in sensitive watersheds such as the Chesapeake Bay, projected operational costs of $11 per kgN are well below the costs cited for upgrading existing water treatment plants.     

Current velocity influences the facilitation and removal of algae by stream grazers

The modification of flows in lotic ecosystems can have dramatic effects on abiotic and biotic processes and change the structure of basal trophic levels. In high-gradient streams, most of the biota are benthic, and decreased flow may homogenize and reduce benthic current velocity, potentially changing stream ecosystem function. Grazing by macroinvertebrates is an important component of stream function because grazers regulate energy flow from primary producers to higher trophic levels. We conducted an experiment to examine how macroinvertebrate grazers facilitated or removed algal biomass across a gradient of benthic current velocity (0–40 cm s^?1). We chose three grazers (Drunella coloradensis, Cinygmula spp., and Epeorus deceptivus) from a montane stream and conducted our experiment using 24 artificial stream channels that had three treatments: no grazers (control), single-grazer, and combined-grazer treatments. In the absence of grazers, algal biomass increased with benthic current velocity. Grazer treatments differed from the control in that more algal biomass was removed at higher velocities, whereas algal accrual was largely facilitated at low velocities. The transition from facilitation to removal ranged from 4.5 to 5.9 cm s^?1 for individual grazer treatments and occurred at 11.7 cm s^?1 for the combined-grazer treatment. Our data suggest that velocity plays a significant role in the facilitation and removal of algae by macroinvertebrate grazers. Additionally, the patterns revealed here could have general implications for algal accrual in systems where flow is reduced.     

Removal of 2,4-dinitrotoluene from concrete using bioremediation,agar extraction,and photocatalysis

Three methods, i.e. bioremediation by application of bacteria-laden agar, physical absorption of DNT by agar, or illumination by UV light were evaluated for the removal of 2,4-dinitrotoluene (DNT) from building-grade concrete. DNT biodegradation by Pseudomonas putida TOD was turned "on" and "off" by using toluene as a co-substrate thus allowing for rate-limiting step assessment. Bioremediation efficiency can be > 95-97% in 5-7 d if the process occurs at optimum growth temperature with the biological processes appearing to be rate-limiting. Sterile agar can remove up to 80% of DNT from concrete thus allowing DNT desorption and biodegradation to be conducted separately. Photoremediation results in 50% DNT removal in 9-12 d with no further removal, most likely due to mass transfer limitations.     

Thioltransferase in human red blood cells: kinetics and equilibrium

Thioltransferase from human red blood cells (HRBC TTase), coupled to GSSG reductase, catalyzed glutathione (GSH)-dependent reduction of prototype substrates hydroxyethyl disulfide (HEDS) and sodium S-sulfocysteine as well as of other homo- and heterodisulfides, including the protein mixed disulfide albumin-S-S-cysteine. Whereas apparent KM values for the substrates varied over more than a 20-fold range, the Vmax values agreed quite closely, usually within less than a factor of 2, suggesting that initial interaction of oxidized substrate with enzyme is not rate determining. HRBC TTase was inactivated by iodoacetamide (IAA), and this was prevented by pretreatment with disulfides. The pH dependence of IAA inactivation gave a remarkably low apparent pKa of 3.5, which was independent of ionic strength (0.05-2 M). At pH 6, one radiolabeled carboxyamidomethyl moiety was bound to the enzyme after treatment with [14C]IAA. This unusual thiol reactivity suggests that the active-site cysteine moiety of the TTase may be involved in a hydrogen bond with a carboxylate moiety. In contrast, the pH dependence for GSH-dependent TTase catalysis of disulfide reduction displayed an inflection point near pH 8.0, also suggesting that the initial reaction of oxidized substrate with the active-site thiol is not involved in rate determination. Two substrate kinetic studies of HRBC TTase and rat liver TTase (e.g., [GSH] and [HEDS] varied independently) gave patterns of intersecting lines on double-reciprocal plots (1/v vs 1/S), indicating a sequential mechanism for the TTase reactions, rather than a ping-pong mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)     

巢湖蓝藻与农业废弃物共热解制取生物质油研究

采用蔗渣、玉米秸秆和棉花秸秆3种废弃物与蓝藻进行混合共热解试验,考察废弃物的加入对蓝藻热解液体产率及组分的影响。结果表明:添加3种废弃物均使共热解液体产率呈下降趋势。当蓝藻与废弃物以1∶1混合共热解时,以蓝藻和玉米秸秆共热解液体产率最高,为61.8%,且除苯酚类以外,液体产物组分与单一蓝藻热解产物组分相近,含氮化合物含量明显降低,相对含量由18.49%降至8.15%。与其它2种废弃物相比,蓝藻与玉米秸秆在适当比例下的共热解有利于改善热解油品质。     

Biotechnological potential of immobilized algae for wastewater N, P and metal removal: A review

This presentation comprises a review on the use of immobilized algae for wastewater nitrogen, phosphorus and metal removal purposes. Details of the use of immobilized algae, the techniques of immobilization and the effects of immobilization on cell function are included. Particularly relevant in their use for heavy metal removal from wastewaters; upon enriching the biomass in metal, can be recoverd, thereby providing economic advantages. The use of immobilized microalgae in these processes is very adequate and offers significant advantages in bioreactors. The future of this area of algal cell biotechnology is considered.     

Interactions between a stream caddisfly and the algae on its case: factors affecting algal quantity

1. Field experiments were conducted to examine interactions between larvae of the caddisfly Gumaga nigricula and the algae (primarily diatoms) located on their sand grain cases. Floating experimental enclosures were placed in sunlit pools of a California stream. Treatments applied to occupied cases, or to those from which caddisflies had been removed, included variations in grazer density, addition of nutrients, and modification of illumination using shade cloth. 2. Neither faecal-enriched agar in empty cases nor injections of faecal material into plugged cases affected case chlorophyll a concentration; injected nutrients (N and P), however, did increase chlorophyll a concentration. Faecal material may be nutrient poor, or nutrients may not be readily released. In addition, the relatively impermeable case wall may reduce the likelihood that nutrients from caddisflies reach the algae on the outer case surface. 3. Although a Gumaga larva may graze algae from its own case, grazing by conspecifics and the caddisfly Helicopsyche borealis causes a greater reduction in the chlorophyll a content of cases. 4. Chlorophyll a content of empty cases was decreased by experimental reduction of light. Because of shading associated with burrowing, chlorophyll a content of cases occupied by Gumaga was low and was unaffected by experimental light reduction. 5. Removal of Gumaga from its case results in rapid accrual of algae. Thus, the net effect of larval presence is to diminish the algal content of its case.