Enhanced removal of tetracycline via advanced oxidation of sodium persulfate and biochar adsorption

Advanced oxidation of antibiotic tetracycline (TC) is becoming an accessible and efficient technology. The removal of TC from the complex wastewater needs to be lucubrated. In this study, a TC removal system involving degradation and adsorption was established. TC degradation was accomplished by enhanced advanced oxidation via the addition of sodium persulfate (SP) and biochar into simulated wastewater containing Mn²⁺ and TC wastewater. The adsorption of TC and its derivatives was removed by biochar. The results indicate that the optimized reaction parameters were 3.0 g/L of biochar prepared at 600 °C (B600) and 400 mg/L of SP under acidic condition, and the removal percentage of TC was 87.48%, including 74.23% of degradation and 13.28% of adsorption; the anions Cl^?, NO₃^?, and H₂PO₄^? had negligible effects on the removal of TC in this Mn²⁺/B600/SP system. The system also functioned well with an aqueous solution with a high chemical oxygen demand (COD) concentration. Electron paramagnetic resonance (EPR) analysis indicated that ·OH and SO₄^? free radicals were present in the Mn²⁺/B600/SP system. Based on the testing and analysis results, a removal mechanism and potential TC degradation pathway for this system were proposed. TC can be degraded by ·OH and SO₄^? via three degradation pathways. Mn²⁺ can be precipitated as MnO₂, and a part of the TC and its derivatives can be adsorbed on the biochar surface. The Mn²⁺/B600/SP system also performed satisfactorily for a complex aqueous solution with various cations and antibiotics.

     

钴金属-有机骨架活化过硫酸钠降解废水中的盐酸土霉素

采用新制备的钴金属-有机骨架(Co-MOF)和过硫酸钠(PS)分别作为催化剂和氧化剂,并通过Co-MOF活化PS降解废水中的盐酸土霉素,考察Co-MOF浓度、PS浓度、pH及温度对降解盐酸土霉素的影响。SEM、TEM、XRD及XPS等结果证明,Co-MOF成功地被合成。降解实验结果表明,与单独的Co-MOF、PS相比,Co-MOF/PS的降解性能有大幅度的提高。当pH=5、温度30 ℃、Co-MOF为200 mg·L⁻¹以及PS为2 000 mg·L⁻¹时,5 min后对20 mg·L⁻¹盐酸土霉素的降解率最高达到97.1%。在催化剂的重复使用实验中,Co-MOF第4次运行对盐酸土霉素的降解率由97.1%(第1次)降低至82.1%,这表明Co-MOF材料可以重复利用降解盐酸土霉素。Co-MOF降解盐酸土霉素实验反应前后的XRD和XPS数据表明Co-MOF具备良好的稳定性。以上研究结果可为新型高效降解体系的开发及其在水环境污染控制领域的应用提供参考。     

微波法对吸附扑热息痛废水活性炭的再生

通过微波加热的方式对用于扑热息痛废水的吸附的活性炭进行再生处理。考察了再生温度和再生时间两个因素对活性炭吸附性能和得率的影响。在最佳微波再生条件(温度为600℃,微波再生时间为15 min)下结果表明,活性炭在的亚甲基蓝吸附值和得率分别为187.5 mg/g和41.82%。对最佳条件下再生得到的活性炭进行孔结构表征,结果为,比表面积达947.9 m2/g,总孔体积为0.97 m L/g。中孔的比例占到71.18%说明活性炭主要以中孔为主。同时对废活性炭和再生活性炭进行了扫描电镜分析,结果表明,通过微波再生后的活性炭表面杂质明显减少。     

Removal of MCPA from aqueous solutions by acid-activated spent bleaching earth

The removal of MCPA (4-chloro-2-methyl phenoxyacetic acid) from aqueous solutions by activated spent bleaching earth (SBE) was studied as a function of time, initial concentration, adsorbent concentration, and temperature. The Langmuir and Freundlich isotherms were fitted by the adsorption data obtained. The values of Langmuir and Freundlich constants were determined. The adsorption kinetics was described by the Lagergren equation. Mass transfer coefficient and thermodynamic parameters were also calculated. Column experiments were conducted and brekthrough capacities were found for different concentrations and different flow rates. The study demonstrates that acid-treated SBE could be used as an efficient adsorbent for the removal of MCPA-bearing wastewater effluents.     

Entrained-flow adsorption of mercury using activated carbon

Bench-scale experiments were conducted in a flow reactor to simulate entrained-flow capture of elemental mercury (Hg0) by activated carbon. Adsorption of Hg0 by several commercial activated carbons was examined at different C:Hg ratios (by weight) (350:1-29,000:1), particle sizes (4-44 microns), Hg0 concentrations (44, 86, and 124 ppb), and temperatures (23-250 degrees C). Increasing the C:Hg ratio from 2100:1 to 11,000:1 resulted in an increase in removal from 11 to 30% for particle sizes of 4-8 microns and a residence time of 6.5 sec. Mercury capture increased with a decrease in particle size. At 100 degrees C and an Hg0 concentration of 86 ppb, a 20% Hg0 reduction was obtained with 4- to 8-micron particles, compared with only a 7% reduction for 24- to 44-micron particles. Mercury uptake decreased with an increase in temperature over a range of 21-150 degrees C. Only a small amount of the Hg0 uptake capacity is being utilized (less than 1%) at such short residence times. Increasing the residence time over a range of 3.8-13 sec did not increase adsorption for a lignite-based carbon; however, increasing the time from 3.6 to 12 sec resulted in higher Hg0 removal for a bituminous-based carbon.     

废旧碱性电池-活性污泥炭的制备及对废水中Cd2+的吸附

以污水厂污泥为主要原料,掺杂不同量的废旧碱性电池电极材料,采用ZnCl2活化法制备出废旧碱性电池-活性污泥炭,表征分析污泥炭样品的碘吸附值、BET、FT-IR、SEM-EDX、XRD和Zeta电位,并进行污泥炭Cd2+吸附实验。结果表明,电池材料掺杂量为25%时,改性污泥炭吸附性能最优,碘吸附值和比表面积分别达到543.0 mg·g-1和426.5 m2·g-1,中孔孔径集中在3~4 nm左右,Zeta电位为-16.30 mV;对比纯污泥炭,废电池-污泥炭吸附金属离子性能更优,Cd2+吸附量增加了近60%,而ZnCl2活化剂用量减少了40%;回归分析发现,准二级动力学和Langmuir等温方程式适用于描述废电池-污泥炭对Cd2+的吸附行为。     

新型过硫酸盐活化技术降解有机污染物的研究进展

在利用过硫酸盐氧化降解有机污染物过程中,以过硫酸盐活化所产生强氧化性的硫酸根自由基至为关键,综述了近来过硫酸盐的新型活化技术,其中以零价金属材料,含铁矿石,含铁复合材料,活性炭及含碳复合材料,含醌结构有机物活化为主线展开。通过介绍各种活化机理以及相应活化技术在降解有机污染物的研究,继而提高过硫酸盐降解有机污染物的潜在研究与应用价值。     

Removal of carbonyl sulfide using activated carbon adsorption

Wastewater treatment plant odors are caused by compounds such as hydrogen sulfide (H2S), methyl mercaptans, and carbonyl sulfide (COS). One of the most efficient odor control processes is activated carbon adsorption; however, very few studies have been conducted on COS adsorption. COS is not only an odor causing compound but is also listed in the Clean Air Act as a hazardous air pollutant. Objectives of this study were to determine the following: (1) the adsorption capacity of 3 different carbons for COS removal; (2) the impact of relative humidity (RH) on COS adsorption; (3) the extent of competitive adsorption of COS in the presence of H2S; and (4) whether ammonia injection would increase COS adsorption capacity. Vapor phase react (VPR; reactivated), BPL (bituminous coal-based), and Centaur (physically modified to enhance H2S adsorption) carbons manufactured by Calgon Carbon Corp. were tested in three laboratory-scale columns, 6 in. in depth and 1 in. in diameter. Inlet COS concentrations varied from 35 to 49 ppmv (86-120 mg/m3). RHs of 17%, 30%, 50%, and 90% were tested. For competitive adsorption studies, H2S was tested at 60 ppmv, with COS at 30 ppmv. COS, RH, H2S, and ammonia concentrations were measured using an International Sensor Technology Model IQ-350 solid state sensor, Cole-Parmer humidity stick, Interscan Corp. 1000 series portable analyzer, and Drager Accuro ammonia sensor, respectively. It was found that the adsorption capacity of Centaur carbon for COS was higher than the other two carbons, regardless of RH. As humidity increased, the percentage of decrease in adsorption capacity of Centaur carbon, however, was greater than the other two carbons. The carbon adsorption capacity for COS decreased in proportion to the percentage of H2S in the gas stream. More adsorption sites appear to be available to H2S, a smaller molecule. Ammonia, which has been found to increase H2S adsorption capacity, did not increase the capacity for COS.     

Influence of resorcinol chemical oxidation on the removal of resulting organic carbon by activated carbon adsorption

Activated carbon adsorption and chemical oxidation followed by activated carbon adsorption of resorcinol in water has been studied. Three chemical oxidants have been used: hypochlorite, permanganate and Fenton's reagent. The influence of concentrations of resorcinol and activated carbon on adsorption removal rates has been investigated. Both isotherm and adsorption kinetics have been studied. Results are fit well by Freundlich isotherms and adsorption rates of resorcinol were found to follow a pseudo-second-order kinetic model. However, pyrogallol, an intermediate of resorcinol oxidation with permanganate and Fenton's reagent, showed an unfavourable isotherm type. At the conditions investigated, chemical oxidation allows slight reductions of TOC and intermediates formed were found to inhibit the adsorption rate of TOC in the case of permanganate and Fenton's reagent oxidation, likely due to formation of some polymer pyrogallol product. The adsorption process was found to be controlled by pore internal diffusion, which justifies the poor affinity of oxidation intermediates toward activated carbon since molecules of larger size should diffuse rapidly for the adsorption to be effective.     

Ultra-high adsorption of Hg0 using impregnated activated carbon by selenium

Activated carbon was one of the main adsorptions utilized in elemental mercury (Hg⁰) removal from coal combustion flue gas. However, the high cost and low physical adsorption efficiency of activated carbon injection (ACI) limited its application. In this study, an ultra-high efficiency (nearly 100%) catalyst sorbent-Se_x/Activated carbon (Se_x/AC) was synthesized and applied to remove Hg⁰ in the simulated flue gas, which exhibited 120 times outstanding adsorption performance versus the conventional activated carbon. The Se_x/AC reached 17.98 mg/g Hg⁰ adsorption capacity at 160 °C under the pure nitrogen atmosphere. Moreover, it maintained an excellent mercury adsorption tolerance, reaching the efficiency of Hg⁰ removal above 85% at the NO and SO₂ conditions in a bench-scale fixed-bed reactor. Characterized by the multiple methods, including BET, XRD, XPS, kinetic and thermodynamic analysis, and the DFT calculation, we demonstrated that the ultrahigh mercury removal performance originated from the activated Se species in Se_x/AC. Chemical adsorption plays a dominant role in Hg⁰ removal: Selenium anchored on the surface of AC would capture Hg⁰ in the flue gas to form an extremely stable substance-HgSe, avoiding subsequent Hg⁰ released. Additionally, the oxygen-containing functional groups in AC and the higher BET areas promote the conversion of Hg⁰ to HgO. This work provided a novel and highly efficient carbon-based sorbent -Se_x/AC to capture the mercury in coal combustion flue gas.

Selenium-modified porous activated carbon and the interface functional group promotes the synergistic effect of physical adsorption and chemical adsorption to promote the adsorption capacity of Hg⁰.

     

Removal of 2,4-D from aqueous solution by the adsorbents from spent bleaching earth

The removal of 2,4-D (2,4-dichlorophenoxyacetic acid) from aqueous solutions by activated spent bleaching earths (SBE) was studied at 20 degrees C. Experiments were performed as a function of time, initial concentration, dose and particle size of the adsorbent. The Langmuir and Freundlich adsorption equations were fitted by the adsorption data obtained. The values of Langmuir and Freundlich constants were determined. The adsorption kinetic was found to follow Lagergren equation. Both the boundary layer and intraparticle diffusion played important roles in the adsorption rate of 2,4-D. As the size of the adsorbent increased, the time to reach equilibrium increased but adsorption capacity decreased.     

强化活性炭吸附技术深度处理焦化废水的可行性研究

采用混凝沉淀、活性炭吸附以及混凝沉淀 活性炭吸附工艺对焦化厂生化出水进行深度处理.单独混凝沉淀或活性炭吸附均可以将水样中COD降到100 mg/L以下,达到国家污水一级排放标准和冷却用水建议标准.活性炭根据不同的材质和进水而表现出不同的吸附性能,对于焦化厂生化出水,煤质炭Ⅰ和果壳炭均表现出良好的吸附效果,并使出水COD＜100 mg/L,但处理成本较高.混凝沉淀 活性炭吸附工艺充分发挥适合去除大分子污染物的混凝沉淀与适宜去除小分子污染物的活性炭吸附技术两者的协同增效作用,吸附单元采用廉价的煤质炭,使出水水质达到个别生产或生活用水回用标准,并且降低深度处理成本.研究结果表明,混凝沉淀 活性炭吸附作为焦化厂生化出水回用工艺是经济可行的.     

Fe/C微电解-超声波/Fenton氧化-活性炭吸附处理仲丁灵农药废水

采用Fe/C微电解-超声波/Fenton氧化一活性炭吸附处理高色度、高COD、高盐分、高毒性的仲丁灵农药废水.试验结果表明:(1)Fe/C微电解处理仲丁灵农药废水的最佳条件:pH为4,铁屑投加量为0.5 mol/L,Fe与C摩尔比为2:1,反应时间为4h.(2)Fenton氧化的最佳条件:pH为4,FeSO4·7H2O投加量为0.03 mol/L,H2O2投加量为0.4 mol/L,反应时间为2 h.(3)在Fenton氧化的最佳条件下,超声波/Fenton氧化对COD去除率最高(平均约为80%).(4)当吸附时间为2 h、PH为6、活性炭投加量为20 g/L时.COD去除率可达90.5%.(5)采用Fe/C锻电解-超声波/Fenton氧化一活性炭吸附处理后,COD、色度均可达到<污水综合排放标准>(GB 8978-1996)中的一级标准.     

Fenton试剂和活化过硫酸钠氧化降解土壤中的二氯酚和三氯酚

氯酚类物质（chlorophenols, CPs）在环境介质中广泛存在且具有很强环境毒性。为探究化学氧化修复场地氯酚类污染的可行性,通过室内实验、模拟搅拌实验、现场中试,开展应用Fenton试剂和活化过硫酸钠氧化降解土壤CPs的研究。结果表明,化学氧化可有效降解土壤中的CPs,在氧化剂用量和CPs总量摩尔比为15:1时,CaO活化Na2S2O8能高效降解土壤中的二氯酚（2,4-DCP）和三氯酚（2,4,6-TCP）,室内实验和现场中试的去除率均达90%以上,处理后的2,4-DCP和2,4,6-TCP浓度均低于《展览会用地土壤环境质量评价标准》（HJ 350-2007）A类标准限值。Fenton试剂在室内实验中降解率达90%以上,但现场中试对2,4-DCP和2,4,6-TCP的降解率仅为66.1%、23.8%,处理后2,4-DCP浓度仍超过A类标准限值1倍以上。此外,在修复过程中,约70%的2,4-DCP、2,4,6-TCP会向液相转移,因此,需要关注修复系统引入水后污染物向液相中的转移可能造成的二次污染。研究结果可为氯酚类污染土壤的修复提供新思路,并为实际工程应用提供理论依据。     

臭氧-过硫酸钠高级氧化降解土霉素废气

为去除禽畜养殖粪便高温堆肥过程产生的土霉素(OTC)废气,采用臭氧-过硫酸钠(O₃/PS)高级氧化方法,在喷淋装置中降解土霉素(OTC)废气。通过对比不同条件下装置对OTC废气的去除率,考察了O₃及PS对OTC废气去除率及耦合作用。结果表明：O₃/PS喷淋塔对OTC去除率可达94.7%,O₃直接氧化作用的加入使OTC的去除率提高了6.2%~15.9%;加入PS后,OTC的去除率增加了13.9%~23.2%,这是由8.6%~13.7%的·OH氧化作用和4.5%~7.5%的${\rm{SO}}_4^{ \cdot - }$氧化作用引起的。结合高分辨液质联用仪(LC-TOF-MS/MS)分析OTC的降解产物,可以看出,OTC在O₃/PS喷淋塔中经过O₃、·OH和${\rm{SO}}_4^{ \cdot - }$的氧化后,生成了4种主要中间产物,即C₂₀H₁₈N₂O₈、C₂₂H₂₀N₂O₈、C₁₂H₁₆O₂和C₁₃H₂₁O₃。由此可知,OTC废气能被喷淋装置有效去除,并被O₃/PS氧化降解。以上研究结果为含OTC废气的产生、检测和处理提供了参考。     

Catalytic oxidation of TNT by activated carbon

Activated carbon can remove 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitrobenzene (TNB) from aqueous solution and promote oxidation of TNT. After equilibrating a 0.35 mM TNT solution with activated carbon (0.2-1% w/v), HPLC and GC/MS analysis confirmed the presence of 2,4,6-trinitrobenzaldehyde (TNBAld) and 2,4,6-trinitrobenzene (TNB), and provided strong evidence supporting 2,4,6-trinitrobenzyl alcohol (TNBAlc) as an intermediate of TNT oxidation. After 6 d, TNT and its oxidation products were strongly bound to the activated carbon, while TNB was extractable with acetonitrile. Observations indicate that activated carbon catalyzes TNT oxidation to TNBAlc, which is readily oxidized to TNBAld and TNB in the absence of activated carbon under dark conditions. While adsorbed TNB was extractable with acetonitrile, activated carbon promoted rapid TNT oxidation and formation of unextractable residues. Strong binding is attributed to catalyzed oxidation of the TNT methyl group, probably through a free radical mechanism, and subsequent chemisorption of oligomers and polymerized products that are not desorbed from micropores. Our observations indicate TNT oxidation and bound residue formation after sorption by activated carbon increases the effectiveness of activated carbon to decontaminate water.     

四环素在活性炭上的吸附行为及机理

考察了活性炭和四环素的相关性质,并通过静态吸附实验探讨了2种活性炭对四环素的吸附和脱附行为,以及pH值、离子强度等水化学条件对活性炭吸附四环素的影响。结果表明,四环素在活性炭上的吸附基本不受离子强度影响;但随着pH值上升,其吸附量下降。四环素在活性炭上吸附的驱动力可能为两者所含官能团间的氢键作用。     

Enhanced degradation of bisphenol S by persulfate activated with sulfide-modified nanoscale zero-valent iron

Environmental Science and Pollution Research - Sulfide-modified nanoscale zero-valent iron (S-nZVI) has been considered an efficient material to remove heavy metals and organic contaminants. The...     

微波加热再生废弃的净化石油化工废水活性炭

为了对石油化工废水净化处理后的废弃活性炭实现循环利用,提出了在无保护气体和活化气体条件下进行微波加热的方法。主要评估了再生温度和再生时间对再生活性炭的吸附性能和得率的影响。结果表明,在再生温度为600℃,再生时间为15 min时,活性炭的碘吸附能力达到最大值971 mg/g,得率为82.36%。再生活性炭比表面积高达1 028 m2/g,总孔体积为1.23 mL/g,平均孔径为4.89 nm。通过废弃活性炭和再生活性炭进行了SEM对比分析,再生活性炭表面杂质减少,孔隙数量明显增多。