交联壳聚糖/沸石复合吸附剂的制备及性能

用沸石负载由缩水甘油基三乙基氯化铵交联的壳聚糖，制得了性能良好的交联壳聚糖/沸石复合吸附剂。研究了该吸附剂应用性能的影响因素，探讨了该吸附剂的吸附性、沉降性和重复使用性，利用FTIR仪和高倍透射电子显微镜对该吸附剂的结构进行了表征。实验结果表明:壳聚糖的交联度为0.93、交联壳聚糖与沸石的质量比为0.045时，制得的交联壳聚糖/沸石复合吸附剂对腐殖酸的去除率可达81.4%，吸附量为4.07mg/g;交联壳聚糖/沸石复合吸附剂对腐殖酸的吸附性能较沸石有显著提高，沉降时间较交联壳聚糖明显缩短;经二次洗脱后腐殖酸去除率仍可达80.2%，腐殖酸吸附量为4.01mg/g。     

水环境中腐殖酸与镉离子结合作用的影响因素

通过测定不同化学条件下腐殖酸与镉离子作用后的游离态镉离子浓度及其结合率，研究各因素对腐殖酸与镉离子作用的影响。研究结果表明，pH值、离子强度、投加镉离子总浓度、腐殖酸浓度和反应温度均影响腐殖酸与镉离子的结合。pH值在4.5~6.5范围内，随pH值升高，腐殖酸与Cd²⁺的结合率增大，游离态Cd²⁺浓度减少。溶液的离子强度增大对结合反应有抑制作用。投加Cd²⁺总浓度的增大会导致结合态Cd²⁺浓度和游离态Cd²⁺浓度逐渐增加，而其结合率逐渐减小。腐殖酸浓度逐渐增大，使Cd²⁺和腐殖酸的结合率逐渐增大。在20℃~50℃范围内时，随反应温度升高，游离态Cd²⁺浓度逐渐减小，其结合率逐渐增加。     

TiO_2/EP光催化降解水体中微污染磺胺嘧啶的研究

制备了膨胀珍珠岩(EP)为载体的TiO2催化剂(TiO2/EP),对使用较为广泛的抗生素磺胺嘧啶(SDZ)进行了光催化降解研究,探讨了TiO2的负载量、溶液的初始浓度、初始pH、无机离子(HCO3-、SO42-和Cl-)和腐殖酸(HA)对SDZ降解效果的影响。结果表明:SDZ的光催化降解符合一级反应动力学方程;当TiO2最佳负载量为20 wt%,SDZ浓度为5 mg/L,pH=6.7,紫外光照射强度为1 000μW/cm2,反应时间为45 min时,SDZ的降解率达到96%;HCO3-在低浓度时能促进SDZ的光催化降解,高浓度时促进作用不明显;SO42-和Cl-对SDZ的光催化降解有轻微的抑制作用;HA对SDZ光催化降解有显著的抑制作用,浓度越高,抑制作用越强。UV-TiO2/EP是一种去除水体中微污染SDZ的有效方法。     

陶瓷印花废水处理的混凝剂及工艺条件

采用混凝剂聚合氯化铝（PAC）、聚丙烯酰胺（PAM）、聚合硫酸铁（PFS）对陶瓷印花废水进行混凝沉降处理，监测水样的吸光度、浊度、悬浮物，以脱色率、浊度去除率、悬浮物去除率评价混凝处理的效果。结果表明：PAC是陶瓷印花废水沉降处理的理想混凝剂；水样的吸光度、浊度、悬浮物随混凝剂用量增大和沉降时间延长而呈降低趋势，而脱色率、浊度去除率、悬浮物去除率随混凝剂和沉降时间的增大呈增大的趋势；PAC投加量为20mg／L，沉降时间约为24h，水样脱色率达到90．0％，而当PAC投加量达到100mg／L，沉降时间约为4h，陶瓷印花水的脱色率可达到96．0％。证明了药剂用量的增加与沉降时间的延长对混凝过程具有增效作用。     

Phytotoxic activity of crop residues from Burdock and an active substance

Abstract

Problems related to weed management such as outbreaks of herbicide-resistant weeds have recently increased. An interesting approach to such problems is to use plant materials with phytotoxic activity. Burdock (Arctium lappa L.) is a biennial herb belonging to Asteraceae and is cultivated in several countries. The present study investigated the phytotoxic activity of burdock and its active substances. Extracts of both burdock leaves and roots inhibited the shoot and root growth of cress and barnyard grass, where the level of inhibition increased with increasing extract concentration. The leaf extracts had 2.0–2.5 times higher activity than the root extracts. Bioassay-guided separations of the leaf extracts led to isolation of a phytotoxic substance, onopordopicrin. Onopordopicrin significantly inhibited the shoot and root growth of cress and barnyard grass. The concentrations of the substance required for 50% growth inhibition were 0.27 and 0.26?mM for cress shoots and roots, respectively, and 1.86 and 0.35?mM for barnyard grass shoots and roots, respectively. The present results suggest that burdock leaves have high phytotoxic activity and onopordopicrin may play a major role in the activity. Burdock leaves may be a good resource for weed management.     

DOC removal paradigms in highly humic aquatic ecosystems

Background, aim, and scope  Dissolved humic substances (HS) usually comprise 50–80% of the dissolved organic carbon (DOC) in aquatic ecosystems. From a trophic and biogeochemical perspective, HS has been considered to be highly refractory and is supposed to accumulate in the water. The upsurge of the microbial loop paradigm and the studies on HS photo-degradation into labile DOC gave rise to the belief that microbial processing of DOC should sustain aquatic food webs in humic waters. However, this has not been extensively supported by the literature, since most HS and their photo-products are often oxidized by microbes through respiration in most nutrient-poor humic waters. Here, we review basic concepts, classical studies, and recent data on bacterial and photo-degradation of DOC, comparing the rates of these processes in highly humic ecosystems and other aquatic ecosystems. Materials and methods  We based our review on classical and recent findings from the fields of biogeochemistry and microbial ecology, highlighting some odd results from highly humic Brazilian tropical lagoons, which can reach up to 160 mg C L⁻¹. Results and discussion  Highly humic tropical lagoons showed proportionally lower bacterial production rates and higher bacterial respiration rates (i.e., lower bacterial growth efficiency) than other lakes. Zooplankton showed similar δ¹³C to microalgae but not to humic DOC in these highly humic lagoons. Thus, the data reviewed here do not support the microbial loop as an efficient matter transfer pathway in highly humic ecosystems, where it is supposed to play its major role. In addition, we found that some tropical humic ecosystems presented the highest potential DOC photo-chemical mineralization (PM) rates reported in the literature, exceeding up to threefold the rates reported for temperate humic ecosystems. We propose that these atypically high PM rates are the result of a joint effect of the seasonal dynamics of allochthonous humic DOC input to these ecosystems and the high sunlight incidence throughout the year. The sunlight action on DOC is positive to microbial consumption in these highly humic lagoons, but little support is given to the enhancement of bacterial growth efficiency, since the labile photo-chemical products are mostly respired by microbes in the nutrient-poor humic waters. Conclusions  HS may be an important source of energy for aquatic bacteria in humic waters, but it is probably not as important as a substrate to bacterial growth and to aquatic food webs, since HS consumption is mostly channeled through microbial respiration. This especially seems to be the case of humic-rich, nutrient-poor ecosystems, where the microbial loop was supposed to play its major role. Highly humic ecosystems also present the highest PM rates reported in the literature. Finally, light and bacteria can cooperate in order to enhance total carbon degradation in highly humic aquatic ecosystems but with limited effects on aquatic food webs. Recommendations and perspectives  More detailed studies using C- and N-stable isotope techniques and modeling approaches are needed to better understand the actual importance of HS to carbon cycling in highly humic waters.     

添加不同量的腐殖酸对猪粪堆肥中主要养分变化的影响

腐殖酸是一种可以控制堆肥氮素损失的天然固定剂,通过研究腐殖酸对猪粪堆肥过程中主要养分含量变化的影响,确定了腐殖酸的最佳加入量.结果表明,加入5%含量(占鲜猪粪重)的腐殖酸最有利于发酵反应的进行,能够促进有机质的分解,有效控制氮素损失,可使速效钾含量增加,但对有效磷的转化能力影响不大;与其他处理相比,加入5%含量的腐殖酸...     

Sorption–desorption of imidacloprid onto a lacustrine Egyptian soil and its clay and humic acid fractions

Sorption–desorption of the insecticide imidacloprid 1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine onto a lacustrine sandy clay loam Egyptian soil and its clay and humic acid (HA) fractions was investigated in 24-h batch equilibrium experiments. Imidacloprid (IMDA) sorption–desorption isotherms onto the three sorbents were found to belong to a non-linear L-type and were best described by the Freundlich model. The value of the IMDA adsorption distribution coefficient, Kd_ads, varied according to its initial concentration and was ranged 40–84 for HA, 14–58 for clay and 1.85–4.15 for bulk soil. Freundlich sorption coefficient, Kf_ads, values were 63.0, 39.7 and 4.0 for HA, clay and bulk soil, respectively. The normalized soil Koc value for imidacloprid sorption was ～800 indicating its slight mobility in soils. Nonlinear sorption isotherms were indicated by 1/n_ads values <1 for all sorbents. Values of the hysteresis index (H) were <1, indicating the irreversibility of imidacloprid sorption process with all tested sorbents. Gibbs free energy (ΔG) values indicated a spontaneous and physicosorption process for IMDA and a more favorable sorption to HA than clay and soil. In conclusion, although the humic acid fraction showed the highest capacity and affinity for imidacloprid sorption, the clay fraction contributed to approximately 95% of soil-sorbed insecticide. Clay and humic acid fractions were found to be the major two factors controlling IMDA sorption in soils. The slight mobility of IMDA in soils and the hysteresis phenomenon associated with the irreversibility of its sorption onto, mainly, clay and organic matter of soils make its leachability unlikely to occur.     

Characterization of humic acids extracted from the sediments of the various rivers and lakes in China

The humic acids (HAs) isolated from the sediments of the various rivers,lakes,and reservoirs in China were studied using elemental analyzer,fourier transform infrared (FT-IR),and CP/MAS 13C nuclear magnetic resonance (NMR) spectroscopy.The results showed that the HAs were characterized by some common chemical and physicochemical properties,but they also pose some differences in the C-containing functional groups.The C/N,C/H,O/C,and O/H ratios differ widely for the various HAs,showing that the elemental comp...     

Removal of humic substances by biosorption

Fungal pellets of Aspergillus niger 405,Aspergillus ustus 326,and Stachybotrys sp.1103 were used for the removal of humic substances from aqueous solutions.Batchwise biosorption,carried out at pH 6 and 25°C,was monitored spectrophotometrically and the process described with Freundlich’s model.Calculated sorption coeffcients Kf and n showed that A.niger exhibited the highest effciency.A good match between the model and experimental data and a high correlation coeffcient(R2)pointed out to judicious choice of ...