Effect of oxidation treatment on the adsorption and the stability of mercury on activated carbon

Oxidation treatment on the adsorption and the stability of Hg on activated carbon （AC） was inrestigated. Both MnO2-AC and FeCl3-AC were produced during oxidation treatment. The measurement of modified AC＇s mercury adsorption capacity was conducted in a simulated coal-fired flue gas by adsorbing test apparatus. TCLP and column leaching methods were used to test the stability of mercury adsorbed on ACs. The results indicate that the oxidation treatment changed the pore structure of the AC and modified the carbon surface by creating chemical components such as MnO4^-, Mn^4＋, O, NO^3-, Fe^3＋, Cl^-, etc. The Hg sorption capacity on MnO2-AC or FeCl3-AC was about three times higher than that of untreated carbon. In addition, the mercury control cost of each of the formers was about the half cost of the untreated carbon. The stability of Hg absorption was studied, it found that mercury adsorbed on the oxidation treated AC was not better than that of untreated carbon. It could concluded that the insoluble form of Hg is very important to the stability of mercury adsorbed on AC. This study suggests that the FeCl3-AC is the best absorbent for Hg with high adsorption capacity, better Hg adsorption stability in leaching environment, and lower cost among the three ACs tested.

Preparation and SO2 Adsorption Behavior of Coconut Shell-Based Activated Carbon via Microwave-Assisted Oxidant Activation

A series of oxidants supported on coconut shell-based activated carbon(CAC) through microwave irradiation were prepared and characterized using scanning electron microscopy(SEM), N_2 adsorption/desorption analysis, and X-ray photoelectron spectroscopy(XPS). The SO_2 adsorption capacities and rates were evaluated by adsorption tests performed in a fixed bed reactor with a simulated flue gas, and the adsorption isotherm models were validated against the experimental results. The findings revealed that the SO_2 adsorption capacity decreased in the following order: MW-K_2Cr_2O_7-CAC > MWKMnO_4-CAC > MW-H_2O_2-CAC > MW-CAC. The SO_2 adsorption capacities and adsorption rates of the samples increased with an increasing oxidizability of the oxidants owing to the increment of mean pore size and oxygen-containing functional groups. In addition, a high initial SO_2 concentration and a low bed temperature could positively affect the SO2 adsorption. Finally, the Langmuir model validated that SO_2 was mainly adsorbed through chemical adsorption on the sample surfaces.

Characterization of Metal Oxide-modified Walnut-shell Activated Carbon and Its Application for Phosphine Adsorption: Equilibrium, Regeneration, and Mechanism Studies

We prepared a kind of metal oxide-modified walnut-shell activated carbon(MWAC) by KOH chemical activation method and used for PH_3 adsorption removal. Meanwhile, the PH_3 adsorption equilibrium was investigated experimentally and fitted by the Toth equation, and the isosteric heat of PH_3 adsorption was calculated by the Clausius-Clapeyron Equation. The exhausted MWAC was regenerated by water washing and air drying. Moreover, the properties of five different samples were characterized by N_2 adsorption isotherm, SEM/EDS, XPS, and FTIR. The results showed that the maximum PH_3 equilibrium adsorption capacity was 595.56 mg/g. The MWAC had an energetically heterogeneous surface due to values of isosteric heat of adsorption ranging from 43 to 90 kJ/mol. The regeneration method provided an effective way for both adsorption species recycling and exhausted carbon regeneration. The high removal efficiency and big equilibrium adsorption capacity for PH_3 adsorption on the MWAC were related to its large surface area and high oxidation activity in PH_3 adsorption-oxidation to H_3 PO_4 and P_2 O_5. Furthermore, a possible PH_3 adsorption mechanism was proposed.

Study on Coconut Shell Activated Carbon Temperature Swing Adsorption of Benzene and Formaldehyde

Adsorption can be used to recover effectively the volatile organic gases(VOCs)in the exhaust gas from factories through using an appropriate adsorption bed.Due to form a physical or chemical bond,adsorption occurs between the porous solid medium and the liquid or gas multi component fluid mixture.The regeneration capa-city of the adsorbent is as important as the adsorption capacity and it determines the economics of the adsorption system.The regeneration of adsorbent can be realized through changing the pressure or temperature of the system.Here,activated carbon samples from coconut shell were prepared and characterized.Benzene or formal-dehyde in the mixed air was used as the adsorption object,and the adsorption experiment was carried out in a U-shaped bed.Discussed how adsorption was affected by activated carbon type,adsorbate and temperature.The results show that oxidation modifed activated carbon can increase the adsorption effect of form aldehyde,but will reduce the ad sorption effect of benzene,because their ad sorption mechanism is different.At 30℃,the saturated adsorption apacity of AC-0 for benzene is 437.0 mg/g.and that of AC-1 for formaldehyde is 670.5 mg/g.In the experimental range,it is found that the adsorption capacity increases with the decrease of temperature,and their changes are very consistent with the ftted ExpDecay1 function.

Effects of Pre-oxidation Conditions on Adsorption Performance of Activated Carbon Fibers

In order to investigate the effects of pre-oxidation conditions on adsorption performance of activated carbon fibers ( ACFs) ,electrospun polyacrylonitrile ( PAN) fiber webs were adopted as precursors for preparing ACFs. Firstly,the webs were stabilized under different pre-oxidation conditions; secondly,the pre-oxidative fibers were chemically activated by high temperature treatment in nitrogen. Pre-oxidation temperature,heating rate,and treatment time are the main factors on affecting the adsorption performance of the ACFs. Scanning electron microscope ( SEM) , differential scanning calorimeter ( DSC ) ,and Fourier transform infrared spectroscopy ( FTIR ) were used to characterize the structure and property of the pre-oxidative fibers,and the dynamic benzene adsorption capacity of benzene of ACFs was measured. The results indicate that the moderate pre-oxidation condition is necessary to prepare the ACFs with better adsorption capacity,and the optimal oxidation conditions are to increase from room temperature to 230 ℃ with a heating rate of 0. 75 ℃·min - 1 ,held at the peak temperature for 30 min.

The Treatment of Polymer-bearing Wastewater from Refinery by Fenton Oxidation - Activated Carbon Adsorption

To solve the problem of polymer-bearing effluent of crude oil not reaching the standard,deep treatment system of Fenton oxidation-activated carbon adsorption is established in one refinery,and the most suitable condition of Fenton oxidation reaction is determined.Operation results show that CODCrconcentration of effluent treated by the system could be lower than 50 mg/L,and ammonia nitrogen content is less than 3 mg/L,which meets design requirement.

Heterogeneous Oxidation of Methylene Blue with Surface-Modified Iron-Amended Activated Carbon

The present study aims to develop effective adsorption and oxidation of synthetic dye in wastewater by using the newly synthesized iron-amended activated carbon. Recently synthetic dye-containing wastewater has gained more attention due to its mass discharge, high toxicity and low biodegradation. For enhancing adsorption of dye and oxidative regeneration of dye-exhausted activated carbon, the novel amendment of iron-deposited granular activated carbon (GAC) was developed. It was to amend ferrous ion onto the acid-pretreated GAC when pH of iron solution was higher than the pH at point of zero charge (pH, pzc) of the GAC. Methylene blue (MB) in water was adsorbed onto the acid-treated iron- amended GAC (Fe-GAC) followed by single or multiple applications of H2O2. Batch experiments were carried out to study the adsorption isotherm and kinetics indicating adsorption of MB onto the Fe-GAC followed Langmuir isotherm and the pseudo-second order kinetics. The Fe-GACshowed the maximum adsorption capacity (qm) of 238.1 ± 0.78 mg/g which was higher than the virgin GAC with qm of 175.4 ± 13.6 mg/g at 20?C, pH 6 and the initial concentration of 20 - 200 mg/L. The heterogeneous Fenton oxidation of MB in the Fe-GAC revealedthat increasing the H2O2 loading from 7 to 140 mmol H2O2/mmol MB led to enhancing the oxidation efficiency of MB in the GAC from 62.6% to 100% due to the increased generation of hydroxyl radicals. Further enhancement of oxidation of MB in the Fe-GAC was made by the multiple application of H2O2 while minimizing OH radical scavenging often occurring at high concentration of H2O2. Therefore, the acid-treated iron-amended GAC would provide excellent adsorption capacity for MB and high oxidation efficiency of MB in the GAC with multiple applications of H2O2 and optimum iron loading.

Experimental Design Technique on Removal of Hydrogen Sulfide using CaO-eggshells Dispersed onto Palm Kernel Shell Activated Carbon：Experiment,Optimization,Equilibrium and Kinetic Studies

This study presents the use of chicken eggshells waste utilizing palm kernel shell based activated carbon（PKSAC） through the modification of their surface to enhance the adsorption capacity of H2S. Response surface methodology technique was used to optimize the process conditions and they were found to be： 500 mg/L for H2S initial concentration, 540 min for contact time and 1 g for adsorbent mass. The impacts of three arrangement factors（calcination temperature of impregnated activated carbon（IAC）, the calcium solution concentration and contact time of calcination） on the H2S removal efficiency and impregnated AC yield were investigated. Both responses IAC yield（IACY, %） and removal efficiency（RE, %） were maximized to optimize the IAC preparation conditions. The optimum preparation conditions for IACY and RE were found as follows： calcination temperature of IAC of 880 ℃, calcium solution concentration of 49.3% and calcination contact time of 57.6 min, which resulted in 35.8% of IACY and 98.2% RE. In addition, the equilibrium and kinetics of the process were investigated. The adsorbent was characterized using TGA, XRD, FTIR, SEM/EDX, and BET. The maximum monolayer adsorption capacity was found to be 543.47 mg/g. The results recommended that the composite of PKSAC and Ca O could be a useful material for H2S containing wastewater treatment.

Preparation of metal oxide doped ACNFs and their adsorption performance for low concentration SO_2

Metal oxide （TiO2 or Co304） doped activated carbon nanofibers （ACNFs） were prepared by electrospinning. These nanofibers were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and Brunner- Emmett-Teller method （BET）. The results show that the average diameters of ACNFs were within the range of 200-500 nm, and the lengths were several tens of micrometers. The specific surface areas were 1146.7 m2/g for TiO2-doped ACNFs and 1238.5 m2/g for Co304-doped ACNFs, respectively. The electrospun nanofibers were used for adsorption of low concentration sulfur dioxide （SO2）. The results showed that the adsorption rates of these ACNFs increased with an increase in SO2concentration. When the SO2 concentration was 1.0 μg/mL, the adsorption rates of TiO2-doped ACNFs and Co3Oa-doped ACNFs were 66.2% and 67.1%, respectively. The adsorption rate also increased as the adsorption time increased. When the adsorption time was 40 min, the adsorption rates were 67.6% and 69.0% for TiO2-doped ACNFs and Co304-doped ACNFs, respectively. The adsorption rate decreased as the adsorption temperature increased below 60℃, while it increased as the adsorption temperature increased to more than 60℃.

Influence of Nitric Acid Concentration on Characteristics of Olive Stone Based Activated Carbon

In this work we investigated the effect of nitric acid concentration on the pore structure,surface chemistry and liquid phase adsorption of olive stone based activated carbon prepared by mixing process using phosphoric acid and steam as activating agents.Chemicals and textural characterization show that the increase of HNO3concentration increases considerably the total acidic groups but decreases specific surface area and pore volume.The study of adsorption in aqueous solutions of two organics,phenol and methylene blue,on raw and oxidized activated carbon indicates that the treatment of mixed activated carbon with different concentrations of nitric acid improves the adsorbent capacity for methylene blue at HNO3concentrations less or equal to 2 mol·L 1,while it has a negative effect on phenol adsorption.

Activated Carbons Containing Dispersed Metal Oxide Particles for Removal of Methyl Mercaptan in Air

Activated carbons containing dispersed metal oxide particles were prepared by carbonization of phenol resin containing metal compounds followed by steam activation. Acetylacetonates of Fe, Mn and V, and Cu nitrate were used as the sources of metals. The removal of a small amount of methyl mercaptan (CH3SH) in air with these activated carbons was tested in a flow system. Compared with activated carbons without metal oxides, the carbons exhibited high activity for the removal of CH3SH in air. In particular, activated carbon obtained from Novolac containing 5 wt% Cu showed excellent behavior over a long time.

Removal of Technetium (⁹⁹Tc) from Aqueous Waste by Manganese Oxide Nanoparticles Loaded into Activated Carbon

Technetium-99 is a radioactive isotope with a half-life of 2.13 × 105 year. 99Tc is a significant contaminant of concern to the world. For this reason, a detailed understanding of technetium chemistry is essential for the protecting the public and the environment especially after increasing the various applications and uses of isotopes in the medical practices. Therefore, treatment of waste increases prior to the safe discharge to the environment or the storage. The sorption of technetium in the form of pertechnetate on a nano manganese oxide loaded into activated carbon has been investigated. Nano manganese oxide (NMO) was synthesized from manganese chloride and potassium permanganate by co-precipitation and forming a new composite by loading a nanoparticle into a modified activated carbon by different ratios. Modifications of activated carbons using different concentrations of HNO3 (4 M, 6 M and 8 M) are used in prepared composites. Fourier transform infrared spectroscopy (FT-IR), X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) were used to characterize the prepared composites. The adsorption of anions from low level radioactive aqueous waste was examined using batch technique. Different parameters affecting on the adsorption process were studied for the removal of . The results revealed that NMO/AC (4 M, 6 M and 8 M) has a high adsorption efficiency (93.57%, 90.3% and 90.3%) respectively compared to NMO and AC which have a lower adsorption efficiency (41% and 38.9%) respectively. Moreover, the adsorption isotherm belonged to Freundlich model, the adsorption data followed pseudo-second order model and the thermodynamic study indicated that the adsorption of on Nano-composites was an exothermic and spontaneous process.

活性炭负载TiO_(2)催化臭氧的造纸废水处理方法研究

造纸废水的处理一直是水利水电工程关注的重点项目。造纸废水中含有大量的污染物质,若是直接排放到环境中,将会对环境造成严重危害。为此,研究一种活性炭负载TiO_(2)催化臭氧的造纸废水处理方法尤为重要。基于此,从水利水电工程废水储蓄池中采集造纸废水水样,配制TiO_(2)催化剂,制备活性炭,将二者混合形成活性炭负载TiO_(2)催化剂;利用催化剂与臭氧充分接触后发生的氧化反应,去除废水中的有机污染物,从而完成造纸废水的处理。测试结果表明:活性炭负载TiO_(2)催化剂对各种污染物质具有很好的去除效果,且催化剂中TiO_(2)负载量越高,催化剂的去除率越高。随着时间的推移,BOD5逐渐降低,水体中的污染物逐渐被分解和消除,证明了所研究方法在造纸废水处理中的应用效果。

聚醚废浓缩液絮凝上清液脱色工艺研究

本文研究了双氧水氧化、活性炭吸附和二者组合对絮凝上清液脱色的影响。结果表明,双氧水氧化脱色率可以达到88.74%但脱色液随时间延长会有沉淀析出。凹凸棒土、白土、活性炭三种吸附剂脱色效果不理想,活性炭的脱色率可以达到30.69%,脱色上清液没有沉淀析出。双氧水氧化和活性炭吸附组合效果更好,脱色率可以达到94.52%且脱色上清液没有沉淀析出。脱色后的上清液可以作为水基切削液的原料使用。

长江下游某工业园区含低浓度有机氮综合工业废水处理实践

对进水含有低浓度有机氮的工业园区综合废水进行处理,在充分调查企业出水水质及现状污水处理厂运行情况的基础上,采用改良型AO+芬顿氧化+加载澄清+活性炭吸附主体工艺,并对AO工艺进行了针对性的优化,出水满足“准Ⅳ类”水标准要求(TN质量浓度≤12 mg/L)。项目设计规模为2.0×104 m^(3)/d,工程总投资为15819.18万元,直接运行成本为3.863元/m^(3)。在江苏省《城镇污水处理厂污染物排放限值》(DB 32/4440—2022)颁布实施后,出水也满足新标准的要求,主体工艺具有较强的适应性、稳定性及前瞻性。

活性炭负载锌催化剂的制备及其处理煤化工废水的试验研究

为实现煤化工高盐废水水质处理效能的提升,以宁夏生产的煤制活性炭为载体,采用直接浸渍法、沉淀-煅烧法2种负载方法,选取Zn元素作为催化剂的活性组分,制备了用于臭氧氧化降解工艺用催化剂,考察了催化剂对宁夏宁东地区煤化工高盐废水中COD去除情况的探究。结果表明:将活性炭与浓度为0.4 mol/L的氯化锌溶液按照m(活性炭)∶V(溶液)=1∶3的比例混合,完全沉淀后,在氮气环境保护下,在恒定300℃的温度下煅烧2 h,制得活性组分为氧化锌的ZnO/AC催化剂,其比表面积为1063.45 m2/g,COD去除率高达71.7%,处理后废水中Zn^(2+)质量浓度增加99.8882 mg/L,高比表面积有利于发挥物理吸附与化学催化的协同作用,提高活性炭基催化剂的催化性能。该臭氧催化剂催化效果显著,可用于煤化工高盐废水中有机物的去除。

生化+芬顿氧化+臭氧催化氧化+生物活性炭组合工艺在医化废水处理中的应用研究

某医化园区各医化企业废水经企业内污水处理站处理达到纳管标准(COD浓度不超过500 mg/L)后排入下游污水处理厂。目前各企业排水COD_(Cr)浓度在200~450 mg/L之间,废水的BOD_(5)/COD_(Cr)只有0.1左右,可生化性较差,容易对下游污水处理厂造成影响。目的:在医化废水进入下游污水处理厂前,使医化废水COD_(Cr)达标。方法:采用生化+芬顿氧化+臭氧催化氧化+生物活性炭组合工艺对医化废水进行中试研究。中试进水COD_(Cr)浓度在206~284 mg/L之间,中试规模为0.5 m^(3)/h。分别考察生化、芬顿氧化、臭氧催化氧化和生物活性炭工艺对COD_(Cr)的处理效果和组合工艺的整体效果。结果:生化、芬顿氧化、臭氧催化氧化和生物活性炭工艺对COD_(Cr)的平均去除率分别为35%、47%、23%、34%,组合工艺的去除率为83%,出水COD_(Cr)浓度为36~47 mg/L,满足《城镇污水处理厂污染物排放标准》(GB 18918—2002)中一级A标准。结论:该组合工艺具有较好的耐负荷冲击能力,适于医化废水的处理。

类Fenton-PAC耦合工艺应用于氨肟化废水预处理研究

针对氨肟化废水可生化性差和粉末活性炭(PAC)致使MBR膜污堵问题,改进PAC施用模式,降低了PAC流失,同时提高了预酸化工序预处理效果和废水可生化性。吸附试验结果表明,PAC可吸附降低氨肟化废水COD,去除率随PAC投加量增加而提高,PAC对小分子量的丙酮肟去除效果最好。工业应用结果表明,类Fenton-PAC耦合下,主要是环己酮肟被氧化降解为小分子有机物,并被PAC吸附去除;此外,吸附后的PAC可在一定程度上氧化再生、重复利用。类Fenton-PAC去除COD的主要原理为·OH对有机物的氧化降解、活性炭表面含氧官能团的络合作用和吸附网捕。

大型油田含油污泥无害化处理技术及其应用研究

为了减少或消除污泥对环境和人体健康的危害,并实现对其资源化、能源化或再利用,提出大型油田含油污泥无害化处理技术。首先,在预处理阶段,将含油污泥进行破碎和混合均匀。破碎的目的是使污泥中的原油和水分尽可能均匀地分散在每个颗粒中,混合则是为了使污泥中的各种成分充分混合在一起。然后,借助化学氧化处理、活性炭吸附处理、生物处理方式,分别降低含油污泥中固体杂质、含油量,以及有机物质含量。最后,采用深度处理方法,如高温焚烧方法,对生物处理后的含油污泥进行减量化和资源化处理。在测试结果中,含油污泥的含油量下降幅度为5.01%,水分含量的下降幅度为6.61%,固体杂质含量的下降幅度为6.00%。

Removal of airborne microorganisms emitted from a wastewater treatment oxidation ditch by adsorption on activated carbon

Bioaerosol emissions from wastewater and wastewater treatment processes are a significant subgroup of atmospheric aerosols. Most previous work has focused on the evaluation of their biological risks. In this study, however, the adsorption method was applied to reduce airborne microorganisms generated from a pilot scale wastewater treatment facility with oxidation ditch. Results showed adsorption on granule activated carbon （GAC） was an efficient method for the purification of airborne microorganisms. The GAC itself had a maximum adsorption capacity of 2217 CFU/g for airborne bacteria and 225 CFU/g for fungi with a flow rate of 1.50 m^3/hr. Over 85% of airborne bacteria and fungi emitted from the oxidation ditch were adsorbed within 80 hr of continuous operation mode. Most of them had a particle size of 0.65-4.7 μm. Those airborne microorganisms with small particle size were apt to be adsorbed. The SEM/EDAX, BET and Boehm＇s titration methods were applied to analyse the physicochemical characteristics of the GAC. Relationships between GAC surface characteristics and its adsorption performance demonstrated that porous structure, large surface area, and hydrophobicity rendered GAC an effective absorber of airborne microorganisms. Two regenerate methods, ultraviolet irradiation and high pressure vapor, were compared for the regeneration of used activated carbon. High pressure vapor was an effective technique as it totally destroyed the microorganisms adhered to the activated carbon. Microscopic observation was also carried out to investigate original and used adsorbents.