Simultaneous elution of polycyclic aromatic hydrocarbons and heavy metals from contaminated soil by two amino acids derived from β-cyclodextrins

Two highly water-soluble amino acids,which derived from β-CDs,i.e.,glutamic acid-β-cyclodextrin (GluCD) and ethylene-diamineβ-cyclodextrin (EDCD),were synthesized and were examined for their effect on solubilization of anthracene (ANT),complexation of cadmium (Cd2+),and elution removal of ANT and Cd2+ in soil.The results showed that GluCD and EDCD were powerful complexant for ANT and Cd2+.In the presence of 10 g/L GluCD and EDCD,the solubilization of ANT increased by 47.04 and 23.85 times compared to the control,respectively.GluCD resulted in approximately 90% complexation of Cd2+ while 70% complexation was observed for EDCD.Simultaneously,GluCD and EDCD could greatly enhance the elution removal of ANT and Cd 2+ from soil.GluCD resulted in the highest elution efficiency of ANT and Cd2+.With the addition of 10 g/L GluCD,53.5% of ANT and 85.6% of Cd2+ were eluted,respectively.The ANT had a negligible effect on the Cd2+ removal due to different complexing sites of ANT and Cd2+,while Cd2+ enhanced the ANT removal under the addition of GluCD because Cd2+ neutralized the-COOH group of GluCD.Adversely,the removal of ANT was decreased with Cd2+ under the addition of EDCD,this was due to the fact that Cd2+ enhanced the polarity of EDCD molecule and inhibited the complexation between ANT and EDCD.The study suggested that GluCD could be preferred and be successfully applied to remediation of heavy metals or organic compounds in contaminated soil.     

Effects of metal cations on sorption-desorption of p-nitrophenol onto wheat ash

The mutual e ects of metal cations (Cu2+, Pb2+, Zn2+, and Cd2+) and p-nitrophenol (NP) on their adsorption desorption behavior onto wheat ash were studied. Results suggested that Cu2+, Pb2+, and Zn2+ diminished the adsorption and increased the desorption of NP remarkably, while Cd2+ had no such e ect. In contrast, NP diminished the adsorption of Cu2+, Pb2+, and Zn2+ onto ash, however, this suppression e ect depended on the initial concentrations of metal cations. NP had no e ect on Cd2+ adsorption on ash. Fourier transform infrared (FT-IR) and X-ray absorption spectroscopic (XAS) studies suggested the following mechanisms responsible for the metal suppression e ect on NP adsorption: (1) large hydrated Cu2+, Pb2+, and Zn2+ shells occupied the surface of ash and prevent nonspecific adsorption of NP onto ash surface; (2) Cu2+, Pb2+, and Zn2+ may block the micropores of ash, resulting in decreased adsorption of NP; (3) complexation of Cu2+, Pb2+, and Zn2+ was likely via carboxyl, hydroxylic and phenolic groups of wheat ash and these same groups may also react with NP during adsorption. As a “soft acid”, Cd2+ is less e cient in the complexation of oxygencontaining acid groups than Cu2+, Pb2+, and Zn2+. Thus, Cd2+ had no e ect on the adsorption of NP on wheat ash.     

Enhanced flushing of polychlorinated biphenyls contaminated sands using surfactant foam: Effect of partition coefficient and sweep efficiency

Foam flushing is an in situ soil remediation technology based on the traditional surfactant flushing method. The contribution of mobility control to contaminant removal by foam is helpful for improving this technology. Foam flushing of polychlorinated biphenyl (PCB)-contaminated unconsolidated media was performed to evaluate the effect of the partition coefficient (PC) and sweep efficiency (SE) on PCB removal. Column flushing with surfactant solution and foam with different types and concentrations of surfactant was carried out for PCB removal. Two types of quartz sand were investigated to evaluate the Jamin effect on the SE value of the washing agent. The results demonstrate that a small PC value and large SE value are necessary to achieve high PCB removal for foam flushing. Compared with solution flushing, the introduction of foam can effectively control the mobility of the washing agent. Similar to solution flushing, solubilization is a key factor which dominates the removal of PCBs in foam flushing. In addition, the SE value and PCB removal by foam flushing is less affected by particle size. Therefore, foam flushing was proved to be more effective in porous media with low hydraulic conductivity and high porosity. An integrated flushing with water, surfactant solution and foam was performed and the results prove that this technology successfully combines the advantages of solution solubilization and mobility control by foam, and thus further increases the remediation efficiency of PCBs to 94.7% for coarse sand.     

Adsorption of heavy metal ions from aqueous solution by carboxylated cellulose nanocrystals

A novel nanoadsorbent for the removal of heavy metal ions is reported.Cotton was first hydrolyzed to obtain cellulose nanocrystals(CNCs).CNCs were then chemically modified with succinic anhydride to obtain SCNCs.The sodic nanoadsorbent(NaSCNCs) was further prepared by treatment of SCNCs with saturated NaHCO 3 aqueous solution.Batch experiments were carried out with SCNCs and NaSCNCs for the removal of Pb 2+ and Cd 2+.The effects of contact time,pH,initial adsorption concentration,coexisting ions and the regeneration performance were investigated.Kinetic studies showed that the adsorption equilibrium time of Pb 2+ and Cd 2+ was reached within 150 min on SCNCs and 5 min on NaSCNCs.The adsorption capacities of Pb 2+ and Cd 2+ on SCNCs and NaSCNCs increased with increasing pH.The adsorption isotherm was well fitted by the Langmuir model.The maximum adsorption capacities of SCNCs and NaSCNCs for Pb 2+ and Cd 2+ were 367.6 mg/g,259.7 mg/g and 465.1 mg/g,344.8 mg/g,respectively.SCNCs and NaSCNCs showed high selectivity and interference resistance from coexisting ions for the adsorption of Pb 2+.NaSCNCs could be efficiently regenerated with a mild saturated NaCl solution with no loss of capacity after two recycles.The adsorption mechanisms of SCNCs and NaSCNCs were discussed.     

Simultaneous adsorption of lead and cadmium on MnO2-loaded resin

MnO2-loaded D301 weak basic anion exchange resin has been used as adsorbent to simultaneously remove lead and cadmium ions from aqueous solution. The e ects of adsorbent dosage, solution pH and the coexistent ions on the adsorption were investigated. Experimental results showed that with the adsorbent dosage more than 0.6 g/L, both Pb2+ and Cd2+ were simultaneously removed at pH range 5–6. Except for HPO4 2??, the high concentration coexistent ions such as Na+, K+, Cl??, NO3??, SO4 2?? and HCO3??, showed no significant e ect on the removal e ciency of both Pb2+ and Cd2+ under the experimental conditions. The coexistence of Mg2+, Ca2+ caused the reduction of Cd2+ removal, but not for Pb2+. The adsorption equilibrium for Pb2+ and Cd2+ could be excellently described by the Langmuir isotherm model with R2 > 0.99. The maximum adsorption capacity was calculated as 80.64 mg/g for Pb2+ and 21.45 mg/g for Cd2+. The adsorption processes followed the pseudo first-order kinetics model. MnO2-loaded D301 resin has been shown to have a potential to be used as an e ective adsorbent for simultaneous removal of lead and cadmium ions from aqueous solution.     

Influencing factors and degradation products of antipyrine chlorination in water with free chlorine

Owing to its low cost, free chlorine is one of the most common disinfectants for wastewater and drinking water treatment. However, the formation of disinfection byproducts has been found to occur after free chlorine disinfection in recent decades. Antipyrine (ANT), an anti-inflammatory analgesic, has been frequently detected in the aquatic environment. In this work, the removal efficiency of ANT by free chlorine oxidation in ultrapure water was investigated with batch experiments. The influencing factors on the removal of ANT were explored at initial concentrations of ANT from 0.04 to 0.64 mg/L, free chlorine dosage from 0.30 to 1.31 mg/L, and pH from 1.5 to 9.0. The main degradation products were identified by solid phase extraction-gas chromatography-mass spectrometry. The results showed that ANT reacted rapidly with free chlorine in ultrapure water systems and up to 90.6% removal efficiency of ANT was achieved after 25 sec (initial free chlorine 1 mg/L, ANT 0.5 mg/L, pH 7.0). Higher oxidant dosage, lower ANT initial concentration and low pH favor the ANT removal. The main degradation product in ANT chlorination was a monochlorine substitution product (4-chloro-1,2-dihydro- 1,5-dimethyl-2-phenyl-3H-pyrazol-3-one), which can be further chlorinated by free chlorine. In addition, the total organic carbon result indicated that ANT is difficult to be mineralized using chlorine.     

Efficiency of active barriers attaching biofilm as sediment capping to eliminate the internal nitrogen in eutrophic lake and canal

Three active barrier materials (zeolite, ceramicite and light porous media) were applied for preventing nitrogen (N) release from eutrophic lake sediments. Long term experiment of two di erent lake sediments were carried out and the e ect of zeolite dose was evaluated. The results indicated that about 90%–100% of total N in overlying water was eliminated by using zeolite. While the N removal e ciency by ceramic was lower than that by zeolite, and light porous media present the lowest e ciency of 59%. Long term sediment incubation experiments indicated that two eutrophic sediments were both e ective in preventing N release in spite of di erent release characteristics. Bio-zeolite capping technology was able to e ectively inhibit the release of N from the sediment, and the zeolite dose was independently from N removal.     

Selection of appropriate organic additives for enhancing Zn and Cd phytoextraction by hyperaccumulators

Chelant-enhanced phytoextraction is one of the most promising technologies to remove heavy metals from soil. The key of the technology is to choose suitable additives in combination with a suitable plant. In the present study, laboratory batch experiment of metal solubilization, cress seeds germination were undertaken to investigate the metal-mobilizing capability and the phytotoxicity of organic additives, including ethylene diamine triacetic acid （EDTA）, citric acid, acetic acid, oxalic acid, glutamine and monosodium glutamate waste liquid （MGWL） from food industry. Experiments in pots were carried out to study the effects of the additives on Zn and Cd phytoextraction. Furthermore, a leaching experiment with lysimeter was performed to evaluate the environmental risks of additive-induced leaching to underground water. The results showed that EDTA had a strong mobilizing ability for Zn and Cd, followed by mixed reagent （MR） and MGWL. MGWL and acetic acid at 5 mmol equivalent per liter resulted in seed germination index less than 2%. Experiments in pots verified the phytotoxicity of acetic acid and MGWL. Addition of the mixed reagent at 6--10 mmol/kg significantly increased Zn phytoextraction by Thlaspi caerulescens. The same for EDTA and the mixed reagent at 10 mmol/kg by Sedum dfredii. But only mixed reagents could significantly increase Cd phytoextraction by the studied hyperaccumulators. This suggested that the strong chelant was not always the good agent to enhance phytoextraction. S. alfredii combined with 2--10 mmol/kg soil MR was preferred for phytoremediation of Cd/Zn contaminated soils in southern China, this could result in high phytoextraction of Cd/Zn and reduce the leaching risk to underground water than EDTA assisted phytoextration.     

Remediation of Cu and As contaminated water and soil utilizing biochar supported layered double hydroxide: Mechanisms and soil environment altering

Preparing materials for simultaneous remediation of anionic and cationic heavy metals contamination has always been the focus of research. Herein a biochar supported FeMnMg layered double hydroxide (LDH) composites (LB) for simultaneous remediation of copper and arsenic contamination in water and soil has been assembled by a facile co-precipitation approach. Both adsorption isotherm and kinetics studies of heavy metals removal by LB were applied to look into the adsorption performance of adsorbents in water. Moreover, the adsorption mechanisms of Cu and As by LB were investigated, showing that Cu in aqueous solution was removed by the isomorphic substitution, precipitation and electrostatic adsorption while As was removed by complexation. In addition, the availability of Cu and As in the soil incubation experiments was reduced by 35.54%–63.00% and 8.39%–29.04%, respectively by using LB. Meanwhile, the addition of LB increased the activities of urease and sucrase by 93.78%–374.35% and 84.35%–520.04%, respectively, of which 1% of the dosage was the best. A phenomenon was found that the richness and structure of microbial community became vigorous within 1% dosage of LB, which indirectly enhanced the passivation and stabilization of heavy metals. These results indicated that the soil environment was significantly improved by LB. This research demonstrates that LB would be an imaginably forceful material for the remediation of anionic and cationic heavy metals in contaminated water and soil.     

Influence of packing media on nitrogen removal in a subsurface infiltration system

Influence of packing media on nitrogen removal in a subsurface infiltration system was studied. System A was filled with loamy soil and system B was filled with mixed soil of 75% red clay with 25% cinder. Both systems were fed with sewage at the same hydraulic loading of 2 cm/d at continuous operation mode. The same excellent removal performances of COD and T-P could be achieved in both infiltration systems with removal rates about 85% and 98%, respectively. In system A, NH4^ -N removal rate was as high as 96.5% and T-N removal rate was relatively much lower as 55.7%. And in system B, NH4^ -N removal rate was as low as 75.4% and T-N removal rate was relatively much higher as 75.5 %. The difference was attributed to different soil oxidation-reduction condition that was greatly influenced by soil texture in subsurface infiltration system. Loamy soil led to oxidative condition that was favorable to nitrification and disadvantageous to denitrification. The results were just adverse to the system filled with clay. Intermittent operation was adopted to improve nitrogen removal in system B. NH4^ -N removal rate could be increased to about 95% and T-N removal rate could be increased to about 90% at intermittent operation mode in system B. Analysis of nitrogen removal mechanisms indicated that nitrification-denitrification was the primary nitrogen removal path in subsurface infiltration system and crop uptake was another important nitrogen removal way, It was the key to improve the total N removal performance that a suitable packing soil was available to present favorable oxidation-reduction condition for simultaneous nitrification and denitrification.     

零价铁对土壤中硝基苯类化合物的还原作用

用气相色谱-质谱联用仪(GC-MS)对零价铁在常温常压下还原3种土壤中对硝基苯和间二硝基苯进行了研究.结果表明,硝基苯类化合物转化为苯胺等化合物,对硝基苯和间二硝基苯2种化合物在黏土中的还原率分别达到91%和90%.不同土壤物理化学性质与硝基苯类化合物的还原率有密切关系,表现为黏土>轻壤土>砂土的规律;中性偏酸的土壤有利于硝基苯类化合物的还原和降解,降解率随有机质含量升高而增高.     

零价铁去除水中锑(Sb)的研究

锑(Sb)是一种新兴的全球性污染物,在我国西南Sb矿区及周边地区Sb污染严重。本文研究了零价铁(ZVI)对Sb的去除效果,研究了ZVI投加量、Sb的初始浓度、pH值及阴离子等因素的影响。结果表明,ZVI对Sb具有较好的去除效果。通过ZVI对Sb去除动力学拟合,Sb的去除符合一级动力学方程;Sb的去除效率在偏酸性条件下比较高,在pH=5时,去除率达到68.98%;在pH=7时,Sb的去除率仅有23.36%;无机阴离子均在不同程度上影响Sb的去除,特别是PO43-对ZVI去除Sb有明显的抑制作用。     

雾化-多相协同臭氧氧化处理硝基苯废水的动力学研究

硝基苯属于典型的难降解有机化合物,通过雾化-多相协同臭氧氧化技术对硝基苯废水的处理效果进行了分析研究.通过对实验中的主要影响因素进行分析,结果表明,液滴粒径对硝基苯降解速率常数具有负相关性;紫外灯功率、活性炭投加量和水温对硝基苯降解速率常数具有正相关性;pH值和臭氧投加量对硝基苯降解速率常数具有最佳值.雾化-多相协同臭氧氧化技术对硝基苯的降解过程遵从一级化学反应动力学方程.经验动力学方程为：C=C0exp（-4.54＆#215;10-6Q0.50G0.31W0.11t）.     

微生物异化还原铁氧化物体系对硝基苯的降解作用

对地下环境中铁氧化物的生物异化还原作用及其降解硝基苯的特性和效果进行了实验研究.结果表明,铁还原菌对硝基苯具有一定的降解能力,100h后硝基苯降解率>68.5%.微生物异化还原铁氧化物过程对硝基苯具有较好的降解作用,当针铁矿浓度为0.3mg/L时,协同降解效果最好,硝基苯降解率为78.5%.微生物的生长与铁氧化物的还原及硝基苯的降解之间具有明显的相关性.     

Removal kinetics of phosphorus from synthetic wastewater using basic oxygen furnace slag

Removal kinetics of phosphorus through use of basic oxygen furnace slag (BOF-slag) was investigated through batch experiments. Effects of several parameters such as initial phosphorus concentration, temperature, BOF-slag size, initial pH, and BOF-slag dosage on phosphorus removal kinetics were measured in detail. It was demonstrated that the removal process of phosphorus through BOF-slag followed pseudo-first-order reaction kinetics. The apparent rate constant (k_obs) significantly decreased with increasing initial phosphorus concentration, BOF-slag size, and initial pH, whereas it exhibited an opposite trend with increasing reaction temperature and BOF-slag dosage. A linear dependence of k_obs on total removed phosphorus (TRP) was established with k_obs = (3.51 ± 0.11) × 10^− 4 × TRP. Finally, it was suggested that the Langmuir–Rideal (L–R) or Langmuir–Hinshelwood (L–H) mechanism may be used to describe the removal process of phosphorus using BOF-slag.     

Removal kinetics of phosphorus from synthetic wastewater using basic oxygen furnace slag

Removal kinetics of phosphorus through use of basic oxygen furnace slag(BOF-slag)was investigated through batch experiments. Effects of several parameters such as initial phosphorus concentration, temperature, BOF-slag size, initial p H, and BOF-slag dosage on phosphorus removal kinetics were measured in detail. It was demonstrated that the removal process of phosphorus through BOF-slag followed pseudo-first-order reaction kinetics. The apparent rate constant(kobs) significantly decreased with increasing initial phosphorus concentration, BOF-slag size, and initial p H, whereas it exhibited an opposite trend with increasing reaction temperature and BOF-slag dosage.A linear dependence of kobson total removed phosphorus(TRP) was established with kobs=(3.51 ± 0.11) × 10- 4× TRP. Finally, it was suggested that the Langmuir–Rideal(L–R)or Langmuir–Hinshelwood(L–H) mechanism may be used to describe the removal process of phosphorus using BOF-slag.     

有机膨润土负载纳米铁去除废水中硝基苯

用具有良好吸附能力的有机膨润土作载体,通过FeSO4与NaBH4反应制得负载型的纳米铁(NZVL/CTMAB-Bent),用XRD、BET对其性能进行了表征.以硝基苯为目标污染物,试验了 -NZVI/CTMAB-Bent对不同起始浓度硝基苯的去除作用,考察了介质PH对其去除效率的影响,并与相同铁含量的纳米铁(NZVI)进行了比较.此外.还对NZVI/CTMAB-Bent还原硝基苯的机理进行了探讨.结果表明,NZVI/CTMAB-Bent对硝基苯的去除能力远高于相同铁含量的NZVI.也明显优于相同含量的有机膨润土和相同铁含量的NZVI对硝基苯去除率的加和.     

工业铁屑(零价铁)还原硝基苯影响因素研究

通过静态试验,研究了初始硝基苯浓度、零价铁含量和pH值对零价铁还原硝基苯的影响.结果表明,在pH值为7,硝基苯初始浓度为311.25mg/L条件下,零价铁含量分别是100、50和25g/L时,硝基苯的降解速率常数分别是-0.02991、-0.0165和-0.00783min-1,零价铁含量越大硝基苯的降解速率越大;在pH值为7,零价铁含量为50g/L条件下,硝基苯的初始浓度分别是127.5,311.25,467.01mg/L时,硝基苯的降解速率常数分别是-0.01532、-0.01235和-0.00891min-1;在硝基苯初始浓度为311.5mg/L,零价铁含量为50g/L条件下,pH值为2.94时,硝基苯的降解速率最大,pH值为7其次,pH值为11.89时的降解速率最小,酸性环境利于零价铁还原硝基苯的进行.由此可见,硝基苯浓初始浓度、零价铁含量和pH值对硝基苯的还原具有重大影响.     

Quantification of changes in zero valent iron morphology using X-ray computed tomography

Morphological changes within the porous architecture of laboratory scale zero valent iron （ZVI） permeable reactive barriers （PRBs）, after exposure to different groundwater conditions, have been quantified experimentally for different ZVI/sand ratios （10%, 50% and 100%, W/W） with the aim of inferring porosity changes in field barriers. Column studies were conducted to simulate interaction with different water chemistries, a synthetic groundwater, acidic drainage and deionised （DI） water as control. Morphological changes, in terms of pore size and distribution, were measured using X-ray computed tomography （CT）. CT image analysis revealed significant morphological changes in columns treated with different water chemistries. For example, 100% ZVI （W/W） columns had a higher frequency of small pores （0.6 mm） was observed in ZVI grains reacted with typical groundwater, resulting in a porosity of 27%, compared to 32% when exposed to DI water. In comparison, ZVI grains treated with the acidic drainage had higher porosity （44%） and larger average pore size （2.8 mm）. 10% ZVI PRB barrier material had the highest mean porosity （56%） after exposure to any water chemistry whilst 100% ZVI （W/W） columns always had the lowest （34%） with the 50% ZVI （W/W） in between （40%）. These results agree with previously published PRB field data and simultaneously conducted geochemical monitoring and mass balance calculation, indicating that both the geochemical and hydraulic environment of the PRB play an important role in determining barrier lifespan. This study suggests that X-ray CT image analysis is a powerful tool for studying the detailed inter pores between ZVI grains within PRBs.     

O3/UV降解水中有机物机理研究

利用O₃/UV降解了水中的硝基苯、乙醇酸和乙酸. 在硝基苯的降解过程中,当加入对H₂O₂具有催化分解作用的MnO₂时,O₃/UV降解效率明显下降,TOC的去除率甚至比单独臭氧化还低,在相同条件下处理40 min后,O₃/UV、O₃和O₃/UV+MnO₂对溶液TOC的去除率分别为44%、41%和39%.该结果表明中间产物H₂O₂对O₃/UV降解效率的提高具有重要的作用. 另外,有机物本身对自由基链反应是否具有促进作用也直接影响着O₃/UV的降解效率,当目标有机物是对自由基链反应具有促进作用的乙醇酸时,O₃/UV降解效率较高,30 min后乙醇酸的去除率即达76%; 而当目标有机物是对自由基链反应具有抑制作用的乙酸时, O₃/UV对其几乎无降解能力.