玉米芯生物炭对水中活性艳蓝的吸附特性

以玉米芯为原料制备生物炭,采用SEM及比表面积分析仪对其表面形貌及孔结构进行了表征,通过批次吸附试验,研究其对水中活性艳蓝的吸附行为。结果表明:玉米芯生物炭对活性艳蓝的吸附在120 min达到平衡,吸附过程符合准二级动力学方程;Langmuir吸附模型能够很好的模拟吸附等温线,最大饱和吸附量为80.01 mg/g。吸附热力学结果显示:玉米芯生物炭对活性艳蓝的吸附是自发的,升高温度有利于吸附。     

生物质炭去除水中重金属Pb(Ⅱ)的研究进展

生物质炭作为一种高效的、低成本的吸附剂,在重金属污染水处理领域引起了人们的广泛关注和研究。文章首先综述了在不同原料、热解温度及热解时间条件下生物质炭的理化性质的差异,然后阐明了生物质炭吸附重金属Pb(Ⅱ)的主要影响因素,分别是生物质炭投加量、反应溶液温度、pH值和重金属Pb(Ⅱ)初始浓度,最后提出了对生物质炭进一步的研究需求和未来的研究方向,以供参考。     

甲醛改性脐橙皮对重金属Pb(Ⅱ)的吸附

以生物废料脐橙皮为原料,在一定的条件下,与甲醛反应,制取生物吸附剂,考察Pb(Ⅱ)初始质量浓度、吸附时间、溶液pH值对生物吸附剂吸附性能的影响。结果表明:在常温条件下,向15mL、pH 5.0、质量浓度为150mg/L的Pb(Ⅱ)溶液中加入25mg改性脐橙皮,恒温振荡2h,改性脐橙皮吸附剂对溶液中Pb(Ⅱ)的去除率达99.85%。改性脐橙皮吸附剂对Pb(Ⅱ)的吸附在2h左右达到平衡且符合二级动力学方程,生物吸附作用遵循Langmuir等温吸附方程,改性脐橙皮吸附剂的最大吸附容量达到185.19mg/g,最适pH值为4.0～5.5。     

凹凸棒土对废水中Pb(Ⅱ)吸附的初步研究

研究了凹凸棒土对重金属离子Pb(Ⅱ)的吸附性能.考察了平衡时间、凹凸棒土用量、pH等对Pb(Ⅱ)在凹凸棒土上吸附性能的影响.结果表明,凹凸棒土对Pb(Ⅱ)具有较强的吸附性能,在Pb(Ⅱ)质量浓度为9.375×10-3g/L,6 h时达到吸附平衡;凹凸棒土质量浓度在0.05 g/L时,吸附效果较好;Pb(Ⅱ)在凹凸棒土上的吸附受pH影响较大,在pH为6.5~9.5时吸附率达到最大.     

羧基化石墨烯/壳聚糖复合材料对Pb（Ⅱ）的吸附研究

氧化石墨烯/壳聚糖复合材料稳定性高，物理机械性能好受到广泛研究。通过溶液共混法制备了羧基化石墨烯/壳聚糖复合材料，并考察其对Pb(Ⅱ)吸附性能。研究结果表明：复合材料对Pb(Ⅱ)的吸附量随pH值的上升呈现先上升后下降的趋势，对100 mg/L的Pb(Ⅱ)最佳吸附条件是pH值为5,复合材料使用量为1.0 g/L,吸附时间300 min,此时吸附量为95.45 mg/g,吸附率为95.45%。吸附过程符合Langmuir等温线和拟二级动力学模型，说明该吸附过程为单层吸附和化学吸附。     

稻壳对废水中Cr(Ⅵ)吸附及动力学研究

以稻壳为原料,经磷酸预处理后,将其用于废水中Cr(Ⅵ)的吸附。当废水中Cr(Ⅵ)初始浓度为200 mg/L、稻壳投加量为30 g/L、吸附温度为30℃、pH为2.5、吸附时间为2.5 h时,Cr(Ⅵ)的吸附率达91%。稻壳对废水中Cr(Ⅵ)的吸附符合Langmuir等温模型和拟二级吸附动力学模型,相关系数R~2分别是0.993 9和0.999,不是颗粒内扩散控制速率。     

二氧化碳驱动离子液体双水相萃取分离印染废水中痕量Pb(Ⅱ)和Cd(Ⅱ)

制备具有可逆疏水-亲水转变性能的离子液体(ILs),其在室温和常压下与H₂O表现出独特的相行为:在CO₂存在下为单相,而在脱除CO₂时为两相。因此,离子液体-H₂O-CO₂三相体系适合双水相萃取,且无需使用大量的电解质。建立了将该体系用于印染废水中痕量Pb(Ⅱ)和Cd(Ⅱ)分离富集并联用原子吸收光谱仪测定其含量的新方法。结果表明,在pH为8.0时,Pb(Ⅱ)、Cd(Ⅱ)可以被[C₆DIPA][Im]相富集,富集倍率25倍,萃取率达到98.8%,Pb(Ⅱ)和Cd(Ⅱ)检出限分别为0.64 ng/mL和0.13 ng/mL。该方法具有绿色环保、萃取容量大、萃取时间短、灵敏度高等优点。用于标准水样和实际印染废水测定,结果令人满意。     

沙棘籽生物炭对苯酚的吸附特性研究

为促进沙棘籽的资源化利用,以沙棘籽为原材料,采用慢速热解技术分别于300、400、500℃条件下制备生物炭吸附剂(BC300、BC400、BC500),研究其去除水中苯酚的效果。吸附实验结果表明,生物炭的制备温度明显影响其对苯酚的吸附效果,3种温度制备的生物炭对苯酚的吸附能力表现为BC500BC400BC300。苯酚的初始浓度、吸附温度、时间等因素均影响吸附效果。45℃下苯酚初始浓度为20mg/L时,BC500对苯酚的去除率最高,达92.1%,生物炭对苯酚的等温吸附线符合Langmuir模式和Freundlich模式。探明了沙棘籽制备生物炭吸附剂及其去除苯酚的最适条件,可为沙棘籽应用于苯酚等有机污染物的去除提供理论依据。     

Adsorption of aromatic carboxylate ions to black carbon (biochar) is accompanied by proton exchange with water

We examined the adsorption of the allelopathic aromatic acids (AA), cinnamic and coumaric, to different charcoals (biochars) as part of a study on bioavailability of natural signaling chemicals in soil. Sorption isotherms in pH 7 buffer, where the AAs are >99% dissociated, are highly nonlinear, give distribution ratios as high as 10(4.8) L/kg, and are insensitive to Ca(2+) or Mg(2+). In unbuffered media, sorption becomes progressively suppressed with loading and is accompanied by release of OH(-) with a stoichiometry approaching 1 at low concentrations, declining to about 0.4-0.5 as the pH rises. Sorption of cinnamate on graphite as a model for charcoal was roughly comparable on a surface area basis, but released negligible OH(-). A novel scheme is proposed that explains the pH dependence of adsorption and OH(-) stoichiometry and the graphite results. In a key step, AA(-) undergoes proton exchange with water. To overcome the unfavorable proton exchange free energy, we suggest AA engages in a type of hydrogen bond recognized to be of unusual strength with a surface carboxylate or phenolate group having a comparable pK(a). This bond is depicted as [RCO(2)···H···O-surf](-). The same is possible for AA(-), but results in increased surface charge. The proton exchange pathway appears open to other weak acid adsorbates, including humic substances, on carbonaceous materials.     

Removal of Pb(II) from aqueous solutions by carbons prepared from Sal wood (Shorea robusta)

In the present work, physically and chemically activated carbons are prepared using Sal wood (Shorea robusta) sawdust by thermal process and using sulfuric acid as the activation agent to remove Pb(II) from aqueous solutions. Adsorption equilibrium studies have been done at a pH of 4 and a room temperature of 30 °C. It was found that the adsorption isotherms are favorable and chemically activated carbons are better than physically activated carbon in terms of adsorption capacity. Various two-parameter adsorption isotherm models, viz. Freundlich, Langmuir, Temkin and Dubinin-Radushkevich, were used to fit the equilibrium data and it was found that the Freundlich adsorption model provided best-fit. The first-order irreversible unimolecular reaction model and the pseudo-second-order kinetic models were used to fit the kinetic data and it was found that both the models provided good fit. Kinetic and film diffusion studies show that the adsorption of lead(II) on the activated carbons tested in this work are both intra-particle and film diffusion controlled.     

Metal impurities dominate the sorption of a commercially available carbon nanotube for Pb(II) from water

Numerous studies suggested carbon nanotubes (CNTs) as a type of promising sorbent for heavy metals from water and explained the sorption mechanism mainly by oxygen-containing functional groups on CNT surfaces but neglected the potential role of metal catalyst residues in CNTs. This is a first study showing that metal impurities could dominate the sorption of one type of commercially available CNTs (P-CNTs) for Pb(II) from water, which will help to understand and guide environmental applications of CNTs as a sorbent. Sorption capacity of P-CNTs (27.3 mg g(-1)) for Pb(II) was much higher than that of the water-washed P-CNTs (W-CNTs, 4.7 mg g(-1)). SEM-EDS and ICP-MS analyses showed that both P-CNTs and W-CNTs contained metal impurities (mainly Co and Mo) which released into the solutions during the sorption, especially P-CNTs. XAFS examination and precipitation experiments demonstrated that PbMoO(4) formation between Pb(II) and CNT-released MoO(4)(2-) and subsequent precipitation in the sorptive solutions was the dominant mechanism for the apparent sorption of Pb(II) by P-CNTs.     

向日葵盘低酯果胶对水中重金属铜离子的吸附性能

该研究探讨了向日葵盘中的天然低酯果胶对水溶液中重金属铜离子（Cu2+）的吸附性能,检测了果胶用量、果胶溶液的pH值、吸附温度、吸附时间及共存离子的影响作用。结果表明,随着果胶的用量增加,Cu2+的去除率不断升高,但吸附量先增大后降低。而吸附量和去除率均随吸附温度的升高和时间的延长先增大后不变、随果胶溶液pH值的升高先增大后降低,并受共存离子的影响,随二价金属离子含量的增加而降低。Cu2+初始质量浓度在0~200 mg/L范围时,利用Langmuir等温方程拟合得到向日葵盘果胶对Cu2+的最大吸附量为29.94 mg/g。热力学分析表明该吸附反应是自发的、熵值增加的吸热反应。动力学分析证明该吸附过程遵循准二级动力学方程,以静电吸引作用和络合作用为主要驱动力。可见,向日葵盘低酯果胶具有较强的Cu2+吸附性能,可作为一种安全、高效、环保的生物吸附材料应用在Cu2+废水的处理中。     

A novel 4-(2-pyridylazo) resorcinol functionalised magnetic nanosorbent for selective extraction of Cu(II) and Pb(II) ions from food and water samples

This paper describes a novel sorbent based on 4-(2-pyridylazo) resorcinol functionalised magnetic nanoparticles and its application for the extraction and pre-concentration of trace amounts of Cu(II) and Pb(II) ions. The nanosorbent was characterised by Fourier transform infrared spectroscopy, X-ray powder diffraction, thermal analysis, elemental analysis and scanning electron microscopy. The effects of various parameters such as pH, sorption time, sorbent dosage, elution time, volume and concentration of eluent were investigated. Following the sorption and elution of analytes, Cu(II) and Pb(II) ions were quantified by flame atomic absorption spectrometry. The limits of detection were 0.07 and 0.7 μg l^?1 for Cu(II) and Pb(II), respectively. The relative standard deviations of the method were less than 7%. The sorption capacity of this new sorbent were 92 and 78 mg g^?1 for Cu(II) and Pb(II), respectively. Finally this nanosorbent was applied to the rapid extraction of trace quantities of Cu(II) and Pb(II) ions in different real samples and satisfactory results were obtained.     

Speciation of Pb(II) sorbed by Burkholderia cepacia/goethite composites

Bacterial-mineral composites are important in the retention of heavy metals such as Pb due to their large sorption capacity under a wide range of environmental conditions. However, the partitioning of heavy metals between components in such composites is not probed directly. Using Burkholderia cepacia biofilms coated with goethite (alpha-FeOOH) particles, the partitioning of Pb(II) between the biological and iron-(oxyhydr)oxide surfaces has been measured using an X-ray spectroscopic approach. EXAFS spectra were fit to quantitatively determine the fraction of Pb(II) associated with each component as a function of pH and [Pb]. At pH < 5.5, at least 50% of the total sorbed Pb(II) is associated with the biofilm component, whereas the total uptake within the composite is dominated by goethite (> 70% Pb/goethite) above pH 6. Direct comparison can be made between the amount of Pb(II) bound to each component in the composite vs separate binary systems (i.e., Pb/biofilm or Pb/goethite). At high pH, Pb(II) uptake on the biofilm is dramatically decreased due to competition with the goethite surface. In contrast, Pb uptake on goethite is significantly enhanced at low pH (2-fold increase at pH 5) compared to systems with no complexing ligands. The mode of Pb(II)-binding to the goethite component changes from low to high [Pb]. Structural fitting of the EXAFS spectra collected from 10(-5.6) to 10(-3.6) M [Pb]eq at pH 6 shows that the Pb-goethite surface complexes at low [Pb] are dominated by inner-sphere bidentate, binuclear complexes bridging two adjacent singly coordinated surface oxygens, giving rise to Pb-Fe distances of approximately 3.9 A. At high [Pb], the dominant Pb(II) inner-sphere complexes on the goethite surface shift to bidentate edge-sharing complexes with Pb-Fe distances of approximately 3.3 A.     

Comparison of Cd(II), Cu(II), and Pb(II) biouptake by green algae in the presence of humic acid

The present study examines the role of humic acid, as a representative of dissolved organic matter, in Cd(II), Cu(II), and Pb(II) speciation and biouptake by green microalgae. Cellular and intracellular metal fractions were compared in the presence of citric and humic acids. The results demonstrated that Cd and Cu uptake in the presence of 10 mg L(-1) humic acid was consistent with that predicted from measured free metal concentrations, while Pb biouptake was higher. By comparing Cd, Cu, and Pb cellular concentrations in the absence and presence of humic acid, it was found that the influence of the increased negative algal surface charge, resulting from humic acid adsorption, on cellular metal was negligible. Moreover, the experimental results for all three metals were in good agreement with the ternary complex hypothesis. Given that metal has much higher affinity with algal sites than humic acid adsorbed to algae, the contribution of the ternary complex to metal bioavailability was negligible in the case of Cd (II) and Cu (II). In contrast, the ternary complex contributed to over 90% of total cellular metal for Pb(II), due to the comparable affinity of Pb to algal sites in comparison with humic acid adsorbed to algae. Therefore, the extension of the biotic ligand model by including the formation of the ternary complex between the metal, humic acid, and algal surface would help to avoid underestimation of Pb biouptake in the presence of humic substances by green algae Chlorella kesslerii.