Ion-exchange properties of brown algae I. Determination of rate mechanism for calciumhydrogen ion exchange for particles from Laminaria hyperborea and Laminaria digitata

Algal particles from Laminaria hyperborea stipes and Laminaria digitata were exposed to a stream of hydrochloric acid in a continuous flow apparatus, and the ion-exchange process Ca/H was investigated. The exchange rate was shown to depend upon such factors as acid concentration, particle size, agitation and time of acid residence. The results show that the exchange rate followed a first-order reaction in the conditions used, and the exchange velocity was proportional to the logarithm of the hydrochloric acid concentration. Evidence is given which indicates that the exchange process is governed by a film-diffusion mechanism, and the diffusion of calcium across a thin liquid film enveloping the particle is suggested to be the rate-determining step. Exchange experiments with particles from Ascophyllum nodosum show that another rate mechanism has to be considered in this case.     

Bio-hydrogen production from a marine brown algae and its bacterial diversity

The aim of this study was to determine how bio-hydrogen production was related to the composition of the bacterial community in a dark fermentation fed with marine brown algae (Laminaria japonica). The bacterial diversity was ascertained by 16S rDNA PCR-sequencing. A total of 444 mL of bio-hydrogen was produced from 10 g/L of dry algae in a 100 mL of culture fluid for 62 h. The pH varied from 8.74 to 7.05. Active bio-hydrogen production was observed from 24 to 48 h, and maximum bio-hydrogen production was 106 mL over 1 L gas. The bacterial community of the activated sludge consisted of 6 phyla, where H₂ producing and consuming bacteria coexisted. The only detectable bacterial phylum after bio-hydrogen generation with heat-treated (65 °C, 20 min) seeding was Firmicutes. Clostridium and Bacillus species constituted 54% and 46%, respectively, of the bacterial mixture and the most abundant species was Clostridium beijierinckii (34%). These results may provide a better understanding of how different biohydrogen communities affect hydrogen production and aid in the optimization of bio-hydrogen production.     

Biosorption of thorium from aqueous solution by Ca-pretreated brown algae Cystoseira indica

The potential use of a biosorbent, Cystoseira indica, obtained from the Persian Gulf was investigated for the removal of Th (IV) ions from aqueous solutions by considering equilibrium, kinetic and thermodynamic aspects. The FT-IR spectra of unloaded and Th-loaded biomass indicated various functionalities on the biomass surface including hydroxyl, amide and carboxyl groups, which are responsible for the binding of thorium ions. Th (IV) uptake by C. indica was pH dependent. An increase in biosorbent dosage up to 1 g/L caused an increase in the Th (IV) percentage removal. Biosorption process at all studied initial Th (IV) ion concentrations follows the pseudo-second order kinetic model. The biosorption data could be well described by Redlich-Peterson isotherm in comparison to Langmuir and Freundlich isotherms. The maximum sorption capacity of Th (IV) by Langmuir isotherm was estimated to be 169.49 mg/g at 45 °C with pH of 3. The thermodynamic parameters indicated the biosorption of Th on the biomass was a feasible, spontaneous and endothermic process. Th sorption capacity remained unaffected or slightly affected (<10% inhibition) in the presence of several interfering ions such as uranium (VI), nickel (II) and copper (II). The reusability of the biomass was also determined after five sorption-desorption cycles.     

有机废弃物厌氧共发酵制氢研究进展

化石燃料的消耗和有机废弃物的大量排放带来了严重的环境问题,而利用有机废弃物进行厌氧发酵制氢是可持续且环境友好的。为了克服单一底物厌氧发酵制氢存在的因营养元素不均衡、毒性抑制和微生物种类较少等导致氢气产率较低的局限性,不同类型的底物厌氧共发酵制氢技术得以开发,然而现阶段仍然存在过程机理不清楚和关键工艺参数不明确等问题。本文综述了有机废弃物厌氧共发酵制氢的必要性、优点及主要影响因素,归纳了不同有机废弃物混合比、有机负荷、发酵温度、水力停留时间、初始pH以及固液比、搅拌方式和反应器类型等关键工艺参数特征及其范围,分析比较了不同有机废弃物厌氧共发酵体系的氢气浓度及产率、发酵液pH、氨氮和挥发性脂肪酸及其组成等工艺特性,总结了产氢功能菌群及其产氢特性及不稳定系统特征微生物。随后指出了目前研究存在的一些不足,并对其在底物利用范围及其预处理、过程机理、技术完善及其综合评估等方面的研究与应用前景进行了展望,为有机废弃物厌氧共发酵制氢技术的研发与应用提供依据。     

葡萄糖和木糖共发酵的产氢特性

引言化石能源面临枯竭,石油价格不断攀升,摆脱对化石能源的依赖是国内外亟待解决的重大问题。氢气因热值高、可再生且燃烧后无污染,成为21世纪最理想的能源。在众多制取氢气的方法中,厌氧发酵制氢反应条件温和,设备简单,而且可利用的原料来源广泛,从而引起了广泛的关注。     

复合生物絮凝剂BF-12对褐藻胶生产废水絮凝性能的研究

从活性污泥中分离出一株产絮凝剂菌B-12,并鉴定其归属于假单胞菌属。此菌产生的复合生物絮凝剂BF-12为多糖类高分子化合物,其主要成分为氨基己糖。采用此复合生物絮凝剂对褐藻胶生产废水进行处理,探讨了絮凝剂投加量、温度、助凝剂投加量、pH等对处理效果的影响,确定了BF-12絮凝的最适条件为:絮凝剂投加质量浓度为150 mg/L,温度为45℃,Ca2+浓度为0.04 mol/L,pH为8。在此条件下其对褐藻胶生产废水具有较好的处理效果,CODCr、BOD5、SS、NH3-N去除率分别达到94.96%、96.10%、82.28%、81.53%。     

藻类制取生物燃料技术研究中技术路线的选择

分析了藻类制取生物燃料的优点和实现产业化存在的突出问题,从提高养殖浓度、养殖易于收割的大型藻类、开发适合加工高含水量藻类的工艺三个方面提出了研究开发的思路,认为利用烟气中的CO2养殖油藻可以把减排CO2与提高油藻养殖浓度有机地结合;养殖大型海藻生产生物燃料;厌氧发酵法将藻类转化为生物燃料是高效、可行的技术路线。     

响应面法优化海带中总多酚提取工艺及抗氧化活性

采用响应面法优化海带总多酚提取工艺,以海带总多酚对二苯代苦味酸(DPPH)自由基的清除作用来评价其抗氧化活性。结果表明,海带总多酚最佳提取工艺是:提取温度72℃,乙醇体积分数52%,液固比60∶1 m L/g,提取时间40 min。在此条件下,海带总多酚提取率达0.945 mg/g,与理论值0.954 mg/g的相对误差为-0.94%。海带总多酚提取液对DPPH自由基有明显的清除作用,其抗氧化性效果随着提取液浓度的增加而增大,且在同等条件下,海带总多酚对DPPH自由基的清除作用优于没食子酸。说明海带总多酚具有较好的抗氧化作用,是一种优良的天然抗氧化剂。     

响应面法优化海带中总多酚提取工艺及抗氧化活性

采用响应面法优化海带总多酚提取工艺,以海带总多酚对二苯代苦味酸(DPPH)自由基的清除作用来评价其抗氧化活性。结果表明,海带总多酚最佳提取工艺是:提取温度72℃,乙醇体积分数52%,液固比60∶1 m L/g,提取时间40 min。在此条件下,海带总多酚提取率达0.945 mg/g,与理论值0.954 mg/g的相对误差为-0.94%。海带总多酚提取液对DPPH自由基有明显的清除作用,其抗氧化性效果随着提取液浓度的增加而增大,且在同等条件下,海带总多酚对DPPH自由基的清除作用优于没食子酸。说明海带总多酚具有较好的抗氧化作用,是一种优良的天然抗氧化剂。     

Sorbent production from low-ash brown coal

The process for the production of a sorbent upon the carbonization of low-ash brown coal in a fluidized bed in a temperature range of 700–850°C was studied. The dependences of the main characteristics of the sorbent on temperature and the fraction of processed coal were found. The characteristics of the lignite sorbent obtained by the TERMOKOKS-KS technology are presented.     

Ethanol production by co-fermentation of hexose and pentose from food wastes using Saccharomyces coreanus and Pichia stipitis

To improve the conversion rate of a saccharification liquid from food wastes containing pentoses and hexoses into bioethanol, after selecting Saccharomyces coreanus and Pichia stipitis, the respective fermentation and co-fermentation properties were investigated. In the fermentation using S. coreanus, the result under anaerobic condition was better than under aerobic conditions. In the anaerobic fermentation, the concentration of the reducing sugar and glucose remaining after 24 hrs was 9.09 and 1.88 g/L, respectively, with 40.59 g/L of ethanol produced; the ethanol productivity was 1.69 g/L-h. Also, even with the fermentation using P. stipitis, the reducing sugars and glucose were rapidly reduced, with a marked production of ethanol, but the ethanol produced was lower than those under anaerobic and aerobic conditions with the use of S. coreanus. Therefore, for the production of a high concentration of bioethanol from food wastes, ethanol fermentation was induced using S. coreanus until the middle of the fermentation, with P. stipitis used during the latter stage of the fermentation, where the circumstance favored its use, and thus, the carbon source not converted by S. coreanus was later converted to ethanol. As a result, both ethanol production of 48.63 g/L and productivity of 2.03 g/L-h increased over those of the anaerobic fermentation using S. coreanus.     

Divinyl ethers and hydroxy fatty acids from three species ofLaminaria (brown algae)

Three species of brown algae,Laminaria sinclairii, L. saccharina andL. setchellii, have been investigated for the presence of oxylipins. From one,L. sinclairii, three new divinyl ether fatty acids have been characterized as methyl ester derivatives (methyl 12-[1′ (Z),3′(Z)-hexadienyloxy]-6(Z), 9(Z), 11(E)-dodecatrienoate, methyl 12-[1′ (Z), 3′ (Z)-hexadienyloxy]-9(Z), 11(E)-dodecatrienoate, and methyl 14-[1′ (Z),3′ (Z)-hexadienyloxy]-9(Z),11(E)-dodecadienoate, and methyl 14-[1′ (Z),3′(Z)-hexadienyloxy]-5(Z),8(Z),11(Z),13(E)-tetradecatetraenoate) by a variety of spectroscopic methods. In addition, one new [13(S)-hydroxy-6(Z),9(Z),11(E),15(Z)-octadecatetraenoic acid] and four known monohydroxy polyunsaturated fatty acids have been isolated from all three species as their methyl ester derivatives. The occurrence of these compounds in brown algae strongly suggests that these organisms possess an active lipoxygenase(s) with ω6 specificity. A preliminary summary of this work was presented at the XIVth International Seaweed Symposium, Brest, France, August 1992 (10).     

The production of active carbon from brown coal in high yields

The acid-leached char produced in high yield by the pyrolysis of the potassium salt of a brown coal (Yallourn seam, Victoria, Australia) is shown to have an internal surface area in excess of $\text{1100}\text{m}{}^2\text{g}$ without the need for activation. Tabletting, or extrusion, of the potassium salt of the coal permits production of a hard, active carbon as shaped granules. Of the cations investigated — sodium, potassium and magnesium — potassium was unique with regard to the formation of such a highly active char.     

海带中褐藻糖胶的酸提法研究

采用酸提法从海带中提取褐藻糖胶,分别采用MgCl、乙醇分级沉淀法进行纯化.主要探讨了提取时间、温度、pH等因素对提取率的影响.结果表明,在提取温度70 ℃,pH 2.5,70%乙醇浓度,提取3 h,提取率为7.3%.乙醇分级沉淀法提取率高于MgCl法.     

Effects of secondary metabolites from marine algae on feeding by the sea urchin,Lytechinus variegatus

A bioassay was developed to test the hypothesis that secondary metabolites from marine algae affect feeding by sea urchins. During experiments measuring chemoreception and gustation, feeding by the regular sea urchin,Lytechinus variegatus (Lamarck), was inhibited by extracts from the green marine alga,Caulerpa prolifera (Forsskal) Lamouroux andCymopolia barbata (Linneaus) Lamouroux. Cymopol, a monoterpene-bromohydroquinone component ofC. barbata, was partially responsible for the inhibited feeding observed in tests of theCymopolia crude extract. Caulerpenyne, an oxygenated sesquiterpene fromC. prolifera, was responsible for all of the urchin feeding inhibition observed in tests of theC. prolifera crude extract. Feeding was not affected by: (1) extracts from several otherCaulerpa species includingC. mexicana (Sonder) J. Agardh,C. ashmaedii Harvey,C. racemosa v.macrophysa (Kutzing) Taylor, andC. racemosa v.laetevirens (Montagne) Weber-van Bosse; (2) caulerpin, an indole-containing pigment isolated from all of theCaulerpa species exceptC. mexicana; and (3) an extract from the red marine alga,Gracilaria foliifera v.angustissima (Harvey) Taylor, which has no known secondary metabolites. Feeding inhibition was independent of the test diameter which correlated with the reproductive state of the urchins. Feeding inhibition was also independent of the starvation periods between experiments, and the temperature and salinity in ranges tolerated byL. variegatus obtained from the Florida Gulf Coast. The data strongly suggest that at least one alga,Caulerpa prolifera, is chemically defended against a dominant omnivore in its community.     

Ion-exchange properties of brown algae. II. Rate mechanism for calcium-hydrogen ion exchange for particles from Ascophyllum nodosum

The ion-exchange properties of algal particles from A. nodosum have been investigated. The Ca/H ion-exchange rate at hydrogen ion concentration 0·1 n was shown to be strikingly lower, while the selectivity coefficent K was about ten times higher, for A. nodosum than for L. digitata and L. hyperborea stipe particles. Log K showed a marked decrease with increasing calcium equivalent fraction in the algal particles. The higher Ca/H selectivity of algal particles from A. nodosum was shown to be the cause of the observed difference in exchange rate between this alga and the two other species. The ion-exchange rate Ca/H for 36–52 mesh particles from A. nodosum at hydrogen ion concentration 0·1 n was governed by a film-diffusion mechanism and the diffusion of calcium through a thin liquid film enveloping the particles was suggested as the rate-determining step. The rate was particle-diffusion controlled for 10–20 mesh particles. The exchange rate for 36–52 mesh particles increased strongly as the hydrochloric acid concentration was increased from 0·05 to 1 n; this exchange appeared to proceed like a second order reaction at 0·05 n and showed a gradual change to a first order reaction at 1 n-acid.     

Reducing fouling from brown coals by sodium-binding additives

The paper reports on methods to control medium-temperature fouling in brown coal-fired power utilities. Binding of sodium is crucial to prevent deposition of condensable sodium salts in the convection sections of pulverised coal-fired boilers. Experiments using mixtures of candidate additives with different sodium compounds were conducted in a drop tube furnace. Experiments showed that sodium could be effectively captured by clay-type mineral additives, particularly kaolin. The results obtained with inorganic mixtures complement our earlier data using coal particles pre-treated with alumina. For pulverised coal conversion processes based on Victorian brown coal, 10–20 μm kaolin making up 2–3 wt.% of the feed was estimated to effectively reduce fouling.