铜藻基载铁活性炭的制备及其对亚甲基蓝的吸附特性研究

以一种大型海藻——铜藻为原料,Fe Cl3·6H2O为活化剂,采用超声浸渍-原位合成法制备了铜藻基载铁活性炭(Fe/SAC),并以活性炭得率和亚甲基蓝吸附值为指标,通过正交法考察了活化温度、活化时间和浸渍比的影响.同时,采用X射线衍射、扫描电镜和比表面积分析仪对最优结果进行表征,并考察了Fe/SAC吸附亚甲基蓝的热力学与动力学特性.结果表明,Fe/SAC的最优制备工艺条件为活化温度600℃、活化时间1 h、浸渍比1∶1,此时的活性炭得率为39.5%,亚甲基蓝吸附值为255.67 mg·g~(-1);最优工艺条件下制得的Fe/SAC比表面积为558.31 m2·g~(-1),其负载的铁组分主要为Fe3O4和Fe O;亚甲基蓝在Fe/SAC上的吸附过程符合准二级动力学模型,Langmuir等温吸附模型能够很好地描述吸附平衡过程,该吸附是熵增加的自发吸热(ΔS0、ΔG0、ΔH0)过程,升温有利于吸附.     

高比表面生物质炭的制备、表征及吸附性能

以废弃生物质互花米草与棉秆为原料,采用KOH活化制备了高比表面积微孔生物质活性炭.研究了原料类别、浸渍比、炭化温度及保温时间对炭组成与吸附性能的影响,利用氮气吸附、X-射线衍射、红外光谱FT-IR、扫描电子显微镜SEM等技术对活性炭表面物化性质进行了分析,并通过BET方程、DFT密度函数理论及Horvath-Kawazoe方程对比表面积与孔分布进行了表征测定.结果表明,氢氧化钾活化制备互花米草与棉秆活性炭的适宜条件为浸渍比3:1、活化温度800℃、活化时间1.5 h.在此条件下制得的互花米草活性炭与棉秆活性炭的得率为16.36%和11.22%,BET比表面积高达2 825 m2.g-1和2 135 m2·g-1,孔容积分别为1.374 mg·g-1和1.038 cm3·g-1;孔径分布狭窄,95%的孔集中在3 nm以内.该条件下制备的互花米草与棉秆活性炭吸附性能好,对碘的吸附值分别为1 797 mg·g-1和1 251 mg·g-1,亚甲基蓝吸附值为495 mg·g-1和478mg·g-1,均超过了国家水处理用活性炭一级品标准;2种生物质炭样品对水中2,4-二硝基苯酚的Langmuir最大吸附量分别为932 mg.g-1、747 mg·g-1,均优于普通活性炭与活性炭纤维.     

KOH活化法制备牛粪活性炭的研究

以牛粪为原料,采用KOH活化法制备活性炭,并考察了浸渍比、活化剂浓度、活化时间和活化温度等不同制备条件对牛粪活性炭样品性能的影响.实验结果表明,在浸渍比1∶4、KOH质量分数35%、活化时间60min、活化温度700℃条件下制备的活性炭性能最佳,制得的活性炭比表面积为979.8m2·g-1,碘吸附值可达796.37mg·g-1,亚甲基蓝吸附值可达150.30mg·g-1.最后,将制备的牛粪活性炭应用于对Cr(Ⅵ)的吸附,研究了最佳工艺条件下制备的活性炭吸附Cr(Ⅵ)的适宜条件.结果表明,在投加量为8g·L-1时、吸附时间90min、pH值为5和较低温度的适宜条件下,自制牛粪活性炭对Cr(Ⅵ)的吸附量最大.     

咖啡渣制备活性炭工艺及其吸附性能

以咖啡渣为原料,采用真空热解及磷酸溶液辅助活化方式制备出活性炭,重点研究了不同活化参数对咖啡渣制备活性炭性能的影响.结果发现,咖啡渣热解自活化的最佳温度为450℃,在活化温度为600℃、真空度为-0.02 MPa、升温速率为20℃·min-1、活化时间为30 min、浸渍比为1.6条件下制备的活性炭吸附性能最佳,此时活性炭得率为27.1%,比表面积为1250 m~2·g~(-1),碘吸附值为1398.4 mg·g~(-1),亚甲基蓝吸附值为270.32 mg·g~(-1).最佳工艺条件下制备的活性炭吸附100 mg·L~(-1)的Cr(Ⅵ)试验表明,在投加量为7 g·L~(-1)、吸附时间为80 min、pH为3.0和吸附温度为15℃条件下,活性炭对Cr(Ⅵ)的吸附量最大,最大去除率为87%.     

污泥基活性炭的制备、表征及其应用

以城市生活污水厂脱水车间污泥为原料,采用化学活化法(ZnCl2为活化剂)在活化剂浓度为45%、活化温度为600℃、浸渍温度为45℃、活化时间为50min条件下制备污泥基活性炭。对污泥基活性炭进行了孔结构、扫描电镜(SEM)、红外光谱(FTIR)、XRD等表征分析。结果表明:该条件下制备出的污泥基活性炭碘吸附值为427.51mg/g,比表面积为329.48m2/g,大孔、中孔、微孔容积分别为0.19,0.12,0.15cm3/g。平均孔径为3.953nm。将其应用于生活污水处理,考察了污泥基活性炭投加量、pH、吸附时间对其吸附性能的影响。     

亚临界水解预处理稻草秸秆制备活性炭及表征

通过以稻草秸秆的亚临界预处理中产生的残渣作为实验材料,以氯化锌作为活化剂制备具有吸附性能的活性炭,研究了活化温度,活化时间,浸渍时间以及浸渍比等4个因素对生成活性炭的性能影响,设计正交实验制备活性炭.以低温液氮吸附测定活性炭的比表面积和孔容、孔径分布,以扫描电子显微镜(SEM)观测活性炭表面形貌,并以亚甲基蓝(MB)作为吸附质,研究了活性炭对亚甲基蓝的吸附动力学和吸附等温线.结果表明,活化温度900℃,活化时间60 min,浸渍比1∶5,浸渍时间12 h,当氯化锌质量分数为20%时,制得相应活性炭的碘值为1 122.79 mg.g-1,亚甲基蓝吸附值为136.50 mg.g-1.亚甲基蓝在活性炭上的吸附基本符合Langmuir方程,且准二级动力学模型能很好地描述活性炭对亚甲蓝的吸附过程;热力学研究表明,吸附吉布斯自由能(ΔG0)<0,而焓变(ΔH0)>0,说明吸附为吸热的自发反应过程,升温有利于吸附.     

富含中孔与酸性基团的生物质炭的制备与吸附性能

以棉秆基生物质纤维为原料,采用磷酸一步活化法制备了同时富含中孔与含氧酸官能团的新型高比表面棉秆纤维基生物质活性炭,分析了浸渍比、炭化温度及保温时间等操作参数对活性炭纤维组成、得率、孔结构及表面官能团含量的影响,测定了制得的棉秆纤维基活性炭对水中对Pb(Ⅱ)与对硝基苯胺的等温吸附性能,并初步探讨了其吸附机制.结果表明,棉秆纤维基生物质炭孔结构与含氧酸基团因制备条件不同有较大变化,实验条件下制备的棉秆基活性炭纤维产率、中孔孔容与比表面的最大值分别为35.5%、0.91 cm3·g-1、1731 m2·g-1;在3∶2的浸渍比,600℃活化90 min的工艺条件下,制备的样品ACF-01的总孔孔容达1.02 cm3·g-1,比表面积为1 731 m2·g-1,微、中孔比例分别为66%与31%,中孔集中在5 nm以内,富含含氧酸官能团.样品ACF-01对水中Pb(Ⅱ)与对硝基苯胺的Langmuir最大吸附量分别为123 mg·g-1和427 mg·g-1,吸附性能远高于微孔孔容相近的商业活性炭纤维ACF-CK,这表明活性炭ACF-01的中孔和含氧酸官能团在吸附过程中发挥了重要作用.     

微波制备秸秆活性炭及其对甲苯吸附性能的研究

以小麦秸秆为原材料,ZnCl2为活化剂,微波加热辐照制备小麦秸秆活性炭。通过改变浸渍比、微波功率、活化时间等因素制得秸秆活性炭比表面积最大为1 230 m2/g。并将制备的秸秆活性炭和选取的商品活性炭用于甲苯的动态吸附试验,研究秸秆活性炭吸附甲苯的性能。结果表明,单位面积秸秆活性炭和商品活性炭吸附甲苯量分别为0.267、0.276 mg/m2,说明秸秆活性炭和商品活性炭吸附性能相当。同时对吸附结果进行Langmuir方程拟合,相关系数R2为0.997。     

ZnCl_2/CuCl_2复合活化剂制备污泥活性炭及其分形研究

以污水处理厂剩余污泥为原料,以氯化锌和氯化铜为复合活化剂,采用低温炭化及中温活化方法制备了污泥活性炭。经正交优化得到最佳制备条件为:活化温度为534℃,活化时间为60 min,ZnCl2浓度为3.0 mol/L,CuCl2浓度为0.3 mol/L,碘吸附值达到534.0 mg/g。所得污泥活性炭含有大量微孔,同时也含有部分中孔和大孔,BET比表面积为784.89 m2/g,Langmuir比表面积为1 053.69 m2/g;利用污泥活性炭吸附制药废水,实验结果符合Freundlich方程,由此建立的分形吸附模型证明制备的污泥活性炭具有分形特征,其分形维数越高,则粗糙度越大,碘吸附值越高。     

响应面法优化制备污泥基活性炭

利用响应面法进行试验设计,选定炭化温度、升温速率、炭化停留时间及保护气体流量为影响因素,对利用污水厂二次污泥制备污泥基活性炭的工艺条件进行优化.通过响应面法得到了污泥基活性炭的碘吸附值与4种因素之间的非线性回归方程,确定了制备污泥基活性炭的最优工艺条件为:炭化温度530℃、升温速率17℃·min-1、炭化停留时间22 min、保护气体流量280 m L·min-1.在最优条件下,制备的污泥基活性炭碘吸附值为675.9 mg·g-1,比表面积为639.5 m2·g-1,平均孔径为4.1 nm,中孔孔径为3~5 nm;羧基、内酯基和酚羟基含量分别为1.625、0.125和0.375 mmol·g-1,更适合吸附大分子污染物和金属离子.     

Evaluation of phytoextracting cadmium and lead by sunflower, ricinus, alfalfa and mustard in hydroponic culture

Soil contaminated with heavy metals cadmium(Cd)and lead(Pb)is hard to be remediated.Phytoremediation may be a feasible method to remove toxic metals from soil,but there are few suitable plants which can hyperaccumulate metals.In this study,Cd and Pb accumulation by four plants including sunflower(Helianthus annuus L.),mustard(Brassica juncea L.),alfalfa(Medicago sativa L.), ricinus(Ricinus communis L.)in hydroponic cultures was compared.Results showed that these plants could phytocxtract heavy metals, the ability of accumulation differed with species,concentrations and categories of heavy metals.Values of BCF(bioconcentration factor)and TF(translocation factor)indicated that four species had dissimilar abilities of phytoextraction and transportation of heavy metals.Changes on the biomass of plants,pH and Eh at different treatments revealed that these four plants had distinct responses to Cd and Pb in cultures.Measurements should be taken to improve the phytoremediation of sites contaminated with heavy metals,such as pH and Eh regulations,and so forth.     

Oxidation of As(Ⅲ) by potassium permanganate

The oxidation of As(Ⅲ) with potassium permanganate was studied under conditions including pH, initial As(Ⅲ) concentration and dosage of Mn(Ⅶ). The results have shown that potassium permanganate was an effective agent for oxidizing of As(Ⅲ) in a wide pH range. The pH value of tested water was not a significant factor affecting the oxidation of As(Ⅲ) by Mn(Ⅶ). Although theoretical redox analyses suggest that Mn(Ⅶ) should have better performance in oxidization of As(Ⅲ) within lower pH ranges, the experimental results show that the oxidation efficiencies of As(Ⅲ) under basic and acidic conditions were similar, which may be due to the adsorption of As(Ⅲ) on the Mn(OH)2 and MnO2 resulting from the oxidation of As(Ⅲ).     

Chlorobenzenes in waterweeds from the Xijiang River （Guangdong section） of the Pearl River

The Xijiang River is the major source of water for about 4.5 millions of urban population and 28.7 millions of rural population. The water quality is very important for the health of the rural population. The concentration and distribution of chlorobenzenes (CBs) in both water and waterweeds collected from 4 stations in the Xijiang River (Gangdong section) of the Pearl River in April and November were determined. The result showed that nearly every congener of CBs was detected. The total contents of CBs (∑CBs) in the river water ranged from 111.1 to 360.0 ng/L in April and from 151.9 to 481.7 ng/L in November, respectively. The pollution level of CBs in the water in April was higher than that in November. The contents of ∑ CBs in waterweeds ranged from 13.53×102 μg/g to 38.27×102μg/g dry weight (dw). There was no significant difference between April and November in waterweeds. The distribution of CBs in roots, caulis, and leaves of Vallisneria spiralis L. showed different patterns. The leaves mainly contained low-molecular-weight CBs(DCBs), whereas the roots accumulated more PCBs and HCBs. The average lgBCFlip (bioconcentration factor) of CBs ranged from 0.64 to 3.57 in the waterweeds. The spatial distribution character of CBs in the Xijiang River was: Fengkai County ＜ Yunan County ＜Yun'an County ＜ Gaoyao County according to the ∑CBs, and the pollution deteriorated from the upstream to the downstream of the Xijiang River. Further analysis demonstrated that the discharge of waste containing CBs may be the main source of CBs pollution in the Xijiang River.     

Degradation of 2,4-dichlorophenol with a novel TiO2/Ti-Fe-graphite felt photoelectrocatalytic oxidation process

Degradation of 2,4-dichlorophenol(2,4-DCP)was studied in a novel three-electrode photoelectrocatalytic(PEC)integrative oxidation process,and the factors influencing the degradation rate,such as applied current,flow speed of O_2,pH,adscititious voltage and initial 2,4-DCP concentration were investigated and optimized.H_2O_2 was produced nearby cathode and Fe~(2 )continuously generated from Fe anode in solution when current and O_2 were applied,so,main reactions,H_2O_2-assisted TiO_2 PEC oxidation and E-Fenton reaction,occurred during degradation of 2,4-DCP in this integrative system.The degradation ratio of 2,4-DCP was 93% in this integrative oxidation process,while it was only 31% in E-Fenton process and 46% in H_2O_2-assisted TiO_2 PEC process.So,it revealed that the degradation of 2,4-DCP was improved greatly by photoelectrical cooperation effect.By the investigation of pH,it showed that this integrative process could work well in a wide pH range from pH 3 to pH 9.     

Effect of copper on the degradation of pesticides cypermethrin and cyhalothrin

The influence of coexisting copper (Cu) ion on the degradation of pesticides pyrethroid cypermethrin and cyhalothrin in soil and photodegradation in water system were studied.Serial concentrations of the pesticides with the addition of copper ion were spiked in the soil and incubated for a regular period of time,the analysis of the extracts from the soil was carried out using gas chromatography (GC).The photodegradation of pyrethroids in water system was conducted under UV irradiation.The effect of Cu~(2 ) on the pesticides degradation was measured with half life (t_(0.5)) of degradation.It was found that a negative correlation between the degradation of the pyrethroid pesticides in soil and Cu addition was observed.But Cu~(2 ) could accelerate photodegradation of the pyrethroids in water.The t_(0.5) for cyhalothrin extended from 6.7 to 6.8 d while for cypermethrin extended from 8.1 to 10.9 d with the presence of copper ion in soil.As for photodegradation,t_(0.5) for cyhalothrin reduced from 173.3 to 115.5 rain and for cypermethrin from 115.5 to 99.0 min.The results suggested that copper influenced the degradation of the pesticides in soil by affecting the activity of microorganisms.However, it had catalyst tendency for photodegradation in water system.The difference for the degradation efficiency of pyrethroid isomers in soil was also observed.Copper could obviously accelerate the degradation of some special isomers.     

Effects of arsenic on seed germination and physiological activities in wheat seedlings

The effects of arsenic(As)were investigated on seed germination,root and shoot length and their biomass and some other factors to elucidate the toxicity of As.The results showed low concentrations of As(O-1 mg/kg)stimulated seed germination and the growth of root and shoot,however,these factors all decreased gradually at high concentrations of As(5-20 mg/kg).The contents Of O2-,MDA,soluble protein and peroxidase(POD)activity all increased with increasing As concentrations.Soluble sugar content,ascorbate peroxidase(APX),and superoxide dismutase(SOD)activities decreased at low concentrations of As,and increased at high concentrations of As.While acetylsalicylic acid(ASA)and chlorophyll contents,catalase(CAT)activity displayed increasing trend when the concentrations of As was lower than 1 mg/kg,and then decreasing trend.By polyacrylamide gel electrophoresis(PAGE).As induced the expression of POD isozymes of wheat seedlings.As induced the expression of CAT isozymes but inhibited the expression of SOD isozymes of wheat seedlings at concentrations lower than 1 mg/kg.However,As inhibited the expression of CAT isozymes but induced the expression of SOD isozymes at concentrations higher than 5 mg/kg.The results indicated As could exert harmfulness in the early development stage of wheat at inappropriate concentrations.     

Sustainability： A view from the wind-eroded field

This article explores the assessment of sustainability in fields subject to wind erosion. In the first part, simple sustainability audits are examined, as of soil depth and nutrients. Direct measurement of these characteristics has many problems, largely because of huge variability in space and time at all scales. Modelling still has its problems, but it may be possible to overcome many of them soon. It is true that wind erosion preferentially removes soil nutrients, but there are imponderables even here. The nutrient balance in many of these soils includes considerable input from dust. In West Africa, it has been shown that the amounts of calcium and potassium that are added in dust are sufficient to fertilize dispersed crops. In mildly acidic sandy soils, such as those found on the widespread palaeo- aeolian deposits, much of the phosphorus is fixed and unavailable to plants by the time it is removed by wind erosion, so that erosion has no added downside. Most of the nutrients carried by dust have been shown to travel close to the ground （even when they are attached to dust-sized particles）, and so are trapped in nearby fallow strips, and are thus not lost to the farming system. Second, the sustalnabillty of a whole semi-arid farming system is explored. Wind erosion in semi-arid areas （like China, the Sahel and Norflawestern Europe） generally takes place on aeolian deposits of the recent geological past. Most of these soils are deep enough to withstand centuries of wind erosion before they are totally lost to production, and some of these soils have greater fertility at greater depth （so that wind erosion may even improve the soil）. Finally some remarks are made about environmental change in relation to sustainability.     

Bioconcentration kinetics of PCBs in various parts of the lifecycle of the tadpoles Xenopus laevis

Polychlorinated biphenyls （PCBs） in Xenopus laevis have been reported only for a few congeners. Additionally, there is very little information on the ability of Xenopus laevis to bioconcentrate PCBs. To address these issues, the tadpole Xenopus laevis was exposed to Aroclor 1254 mixtures in water at room temperature for 110 d followed by an additional 110 d of nonspiked PCBs in the water for the control group. During the whole process, bioconcentration factors （BCFs） of PCBs ranged from 1180 to 15670. For most PCB congeners, the highest and lowest bioconcentrations of the kinetic curves were found to be remarkably simultaneous, respectively. All 141 PCB congeners under the same experimental conditions had no linear correlation on the lgBCF versus lgKow relationship. The relationship between lgBCFs and lgKow followed a parabolic pattern indicative of selective bioconcentration, suggesting that the kinetic curves of the PCB congeners observed in the lifecycle of the tadpoles may be concentrated due to the amphibian special species and internal metabolism. In contrast, lgBCFs for PCBs were inversely related to lgKow, suggesting that a metabolism of the higher Kow PCB congeners occurred. These results support the author＇s conclusion that the tadpole Xenopus laevis plays major roles in the bioconcentration of PCB congeners, and demonstrated that the exposure kinetic curves of PCB congeners are complex. Besides the amphibian metamorphous development, the lifecycle of the tadpole Xenopus laevis also may be of importance in determining the bioconcentration of PCB congeners.     

Amplification of plasmid DNA bound on soil colloidal particles and clay minerals by the polymerase chain reaction

Polymerase chain reaction(PCR)was used to amplify a 600-base pair(bp)sequence of plasmid pGEX-2T DNA bound on soil colloidal particles from Brown soil(Alfisol)and Red soil(Ultisol),and three different minerals(goethite,kaolinite,montmorillonite). DNA bound on soil colloids,kaolinite,and montmorillonite was not amplified when the complexes were used directly but amplification occurred when the soil colloid or kaolinite-DNA complex was diluted,10- and 20-fold.The montmorillonite-DNA complex required at least 100-fold dilution before amplification could be detected.DNA bound on goethile was amplified irrespective of whether the complex was used directly,or diluted 10- and 20-fold.The amplification of mineral-bound plasmid DNA by PCR is,therefore,markedly influenced by the type and concentration of minerals used.This information is of fundamental importance to soil molecular microbial ecology with particular reference to monitoring the fate of genetically engineered microorganisms and their recombinant DNA in soil environments.     

Arsenic uptake and transport of Pteris vittata L. as influenced by phosphate and inorganic arsenic species under sand cu｜ture

In order to understand the similarity or difference of inorganic As species uptake and transport related to phosphorus in As-hyperaccumulator, uptake and transport of arsenate (As(Ⅴ)) and arsenite (As(Ⅲ)) were studied using Pteris vittata L. under sand culture. Higher concentrations of phosphate were found to inhibit accumulation of arsenate and arsenite in the fronds of P. vittata. The reduction in As accumulation was greater in old fronds than in young fronds, and relatively weak in root and rhizome. Moderate increases, from 0.05 to 0.3 mmol/L, in phosphate reduced uptake of As(Ⅲ) more than As(Ⅴ), while the reverse was observed at high concentrations of phosphate (≥ 1.0 mmol/L). Phosphate apparently reduced As transport and the proportion of As accumulated in fronds of P. vittata when As was supplied as As(Ⅴ). It may in part be due to competition between phosphorus and As(Ⅴ) during transport. In contrast, phosphate had a much smaller effect on As transport when the As was supplied as As(Ⅲ). Therefore, the results from present experiments indicates that a higher concentration of phosphate suppressed As accumulation and transport in P. vittata, especially in the fronds, when exposure to As(Ⅴ); but the suppression of phosphate to As transport in the root or rhizome may be insignificant when P. vittata when exposure to As(Ⅲ) under sand culture conditions. The finding will help to understand the interaction of P and As during their uptake process in P. vittata.