Adsorption of humic acid by powdered activated carbon in saline water conditions

The adsorption of humic acid (HA) by powdered activated carbon (PAC) in saline waters has been examined in the absence and presence of metal salt coagulants. The study showed that adsorption of HA by PAC can be significantly greater in saline water compared to freshwater and low conductivity water. An optimal adsorption was attained at saline concentrations corresponding to synthetic seawater diluted to 12.5-25% of its original concentration. In undiluted synthetic seawater the adsorption of HA from solution by PAC was comparable with that of local tap water in terms of initial adsorption rate and total removal. The enhanced adsorption is believed to be a combination of reduced electrostatic repulsion between the HA and PAC at high salt concentrations, and chemisorption due to chemical bonding between the functional groups. The effects of adding a metal salt coagulant, either aluminium sulphate or ferric chloride, on overall HA removal were found to depend strongly on the coagulant dose, solution pH and the sequence of addition of the PAC and metal salt coagulant. Addition of the PAC shortly before the coagulant was found to give the greatest removal of HA.     

投加粉末活性炭对膜生物反应器性能的影响

采用两组膜生物反应器(反应器1未投加粉末活性炭,反应器2投加粉末活性炭量为500mg/L)研究了在相同的进水和运行条件下其混合液特性和膜过滤阻力的变化.研究发现:加入活性炭可有效延缓混合液的黏度,胞外聚合物(EPS)含量、微细颗粒的含量和膜过滤阻力的增加,而且黏度和EPS含量有较好的线性相关性.分析认为膜孔堵塞仅在很短的时间内(≤1 min)起作用,因此膜孔堵塞模型可并入膜本身阻力模型;大于膜孔径而小于1 μm的颗粒物是形成沉积层的主要物质,而沉积层阻力是膜过滤的主要阻力.     

Adsorption of zinc(II) from water with purified carbon nanotubes

Commercial single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) were purified by sodium hypochlorite solutions and were employed as adsorbents to study the adsorption characteristics of zinc from water. The properties of CNTs such as purity, structure and nature of the surface were greatly improved after purification which made CNTs become more hydrophilic and suitable for adsorption of Zn²⁺. In general, the adsorption capacity of Zn²⁺ onto CNTs increased with the increase of pH in the pH range of 1-8, fluctuated very little and reached maximum in the pH range of 8-11 and decreased at a pH of 12. A comparative study on the adsorption of Zn²⁺ between CNTs and commercial powdered activated carbon (PAC) was also conducted. The maximum adsorption capacities of Zn²⁺ calculated by the Langmuir model are 43.66, 32.68, and with SWCNTs, MWCNTs and PAC, respectively, at an initial Zn²⁺ concentration range of 10-. The short contact time needed to reach equilibrium as well as the high adsorption capacity suggests that SWCNTs and MWCNTs possess highly potential applications for the removal of Zn²⁺ from water.     

Adsorption of disperse dye by powdered activated carbon

The purpose of this laboratory study is to investigate the effectiveness of powered activated carbon (PAC) on the removal of chemical oxygen demand (COD) and color of disperse dye and the effect of PAC particle size on the treatment efficiency. The adsorption isotherm parameters for the Langmuir, Freundlich and BET model are determined using the adsorption data. It has been found that the multilayer BET isotherm yields significantly better fit to the observed data than the monolayer ones. A simplified mass transfer model is proposed in the present work also for estimating the external mass transfer coefficient using the initial adsorption data at low PAC dosage.     

Comparison of the filtration characteristics between biological powdered activated carbon sludge and activated sludge in submerged membrane bioreactors

The filtration performances of submerged membrane bioreactors (SMBR) with and without the addition of powdered activated carbon (PAC) were investigated respectively under the same feed and operation conditions. A series of experiments were conducted to analyze near-critical flux, effect of air-scouring rate and time of stable filtration operation of both systems. The experimental results demonstrated that pronounced flux enhancement was achieved by adding 1.2 g/L PAC. The near-critical flux for the biological powdered activated carbon (BPAC) system was about 32% higher than that for the activated sludge (AS) system. Increasing the air-scouring rate led to a more significant flux improvement for the BPAC system compared to the AS system. Long-term operation indicated that, at constant flux, the TMP increasing rate of the BPAC system could be lagged and thus cause the extension of operating intervals about 1.8 times compared to the AS system. Quantitative calculations showed the total hydraulic resistance of the BPAC system was about 44% lower than that of the AS system, and this decrease was mainly caused by the reduction in cake resistance. Analyses were then made from various aspects such as floc size distribution and apparent viscosity of the mixed liquor to elucidate the major factors giving rise to different filtration characteristics.     

超声波强化活性炭颗粒吸附PFOA和PFOS

研究了20 kHz超声波强化活性炭颗粒吸附不同种类水溶液中全氟辛烷磺酸（PFOS）和全氟辛酸（PFOA）的动力学。结果表明：平衡吸附被证实符合BET多层等温吸附,最大单层吸附容量为qmPFOS>qmPFOA;在PFOS和PFOA初始浓度为50 mg/L时超声波辐照下活性炭颗粒吸附符合表观拟二级动力学关系,平衡吸附容量和起始吸附速率分别为qePFOS>qePFOA和 hPFOS> hPFOA;在去离子水（MQ）中的PFOS和PFOA 最大单层吸附平衡容量qm和平衡吸附容量qe及起始吸附速率h和吸附动力学常数K均大于预处理或未预处理后的垃圾渗滤地表水（Pre-GW和GW）中对PFOS和PFOA的平衡吸附量和吸附动力学常数;20 kHz超声波强化活性炭颗粒吸附PFOS和PFOA效果明显,其吸附动力学常数增强因子为7.7和4.4。     

粉末活性炭静态吸附水中硝基酚的试验研究

研究了常温(20℃)条件下粉末活性炭(PAC)对水中3-硝基酚、4-硝基酚、2,6-二硝基酚和2,4-二硝基酚4种硝基酚的静态吸附规律;并对照研究了未驯化的灭活活性污泥存在时,PAC对硝基酚的吸附性能。结果表明:PAC对4种硝基酚的吸附能力远大于灭活活性污泥;当硝基酚与PAC的质量比值在0.2~1.0时,PAC对4种硝基酚的吸附在60 min内可达到平衡,且均符合Langmiur吸附模型;用Langmiur吸附模型对试验数据进行拟合,得出了PAC对4种硝基酚的饱和吸附容量和吸附系数。     

Adsorption equilibrium of copper ion and phenol by powdered activated carbon, alginate bead and alginate-activated carbon bead

The adsorption equilibrium characteristics for single and binary components of copper ion and phenol onto powdered activated carbon, alginate bead and alginate-activated carbon (AAC) bead were studied. Adsorption equilibrium data of phenol and copper ion onto the adsorbents could be represented by Langmuir equation. The adsorption capacity of Cu²⁺ onto different adsorbents was in the following order: alginate bead > AAC bead > powdered activated carbon (PAC). On the other hand, that of phenol was: PAC > AAC bead > alginate bead. Multi-component equilibrium data were correlated by three different models. Among them the ideal adsorbed solution theory (IAST) gave the best fit to our data. And the adsorption amount of Cu²⁺ onto AAC bead was greater than that of phenol in the binary components.     

Removal of organic matter by coagulation enhanced with adsorption on PAC

The removal of humic acids and phenol from model solution by coagulation and adsorption on powdered activated carbon (PAC) was investigated. A PAX XL-69 polyaluminum chloride was applied as a coagulant. The adsorption of humic acids and phenol on activated carbon for single- and bi- component solutions was studied. It was found that coagulation without PAC addition was less effective than the adsorption-coagulation integrated system. Coagulation enhanced with adsorption on activated carbon was more effective when coagulation was preceded by adsorption than when the two processes were carried out simultaneously. The best results were obtained at pH 7. Phenol and color were removed pletely, UV₂₅₄ absorbance was reduced by about 99% and COD-Mn was reduced by 81-89%.     

Hybrid PAC-submerged membrane system for trace organics removal: I. Adsorption kinetics study of PAC in a bubbled solution

Part I of this study presents a theoretical method combined with experiments to determine the adsorption kinetics of powdered activated carbon (PAC) in the hybrid PAC-submerged membrane (SM) system with air bubbling for trace organics removal. The homogeneous surface diffusion model (HSDM) was applied to describe the kinetics of the adsorbate uptake. The differences between the model solutions and the corresponding experimental results were minimized by means of Levenberg–Marquardt algorithm so that two kinetic parameters D_S and k_f involved in HSDM were obtained simultaneously. The D_S was found to be 1.14 × 10⁻¹⁶ m²/s and the k_f value was correlated with the bubbling rate (Q_b) and carbon dosage (C_c), which are required in the modeling of the hybrid PAC-SM system presented in Part II of this study. The k_f was enhanced from 1.18 × 10⁻⁴ to 4.18 × 10⁻⁴ m/s when the bubbling intensity increased in the intermittent bubbling tests, suggesting that from energy consumption point of view, the high intensity intermittent bubbling is more efficient in improving the liquid film mass transfer than continuous bubbling with the same net bubbling rate.     

Adsorption separation of raffinose from sucrose by activated carbon: Equilibrium,kinetics and dynamic breakthrough

Separation of oligosaccharides with a varied number of monosaccharides is an important issue in food chemistry. Raffinose, a functional oligosaccharide, has attracted increasing attentions due to its strong proliferative effect on bacteria. Industrially, cottonseed meal is an important resource for producing raffinose; however, raffinose extracted from the cottonseed meal contains a significant amount of sucrose that debases raffinose’s quality. In this work, an adsorptive separation of raffinose and sucrose on activated carbon was reported. Adsorption isotherms, adsorption kinetics and dynamic column adsorption–desorption were investigated. The activated carbon chosen has a significantly higher adsorption capacity of raffinose (0.60~0.65 g/g) than sucrose (0.35~0.40 g/g) at the equilibrium concentration studied (~35 g/L) and temperature from 293 K to 333 K. Adsorption isotherms and kinetics were fitted by the Freundlich isotherm model and the pseudo-second-order model, respectively. The effect of flow-rate and initial feed concentration on dynamic adsorption were investigated; meanwhile, the separation performance was further confirmed from dynamic desorption using aqueous ethanol of 20% as eluant. Remarkably, raffinose with purity over 90% and recovery of 79.2% could be obtained by the adsorption–desorption cycle using an aqueous feed solution containing 20 g/L of raffinose and 6 g/L of sucrose.     

Adsorption of pollutants on to activated carbon in fixed beds

The adsorption of certain pollutants, namely phenol, p-chlorophenol, sodium dodecyl sulphate and mercuric ions, on to activated carbon has been studied using fixed bed systems. There are three main methods of contacting in solid/liquid adsorption systems, namely batch, fixed bed and fluidized bed systems. In fixed bed adsorption the adsorption rate is determined on the basis of adsorption equilibrium (unfavourable, linear, favourable or completely irreversible) and the controlling mechanism (external film mass transport, internal pore diffusion, internal solid phase diffusion or longitudinal diffusion). One or more of the previous transport mechanisms may be rate controlling depending on the solute-adsorbent system. For an adsorbent like activated carbon which is highly porous both external transport and pore diffusion will be very important. An adsorption model, based on external mass transport and internal pore diffusion, has been applied to the systems to predict theoretical breakthrough curves. These curves have then been compared with experimental data and using a ‘best fit’ technique, an effective pore diffusion coefficient can be determined for each sorbate–carbon system.     

废聚苯乙烯泡沫制备粉状活性炭

针对白色污染,研究了以废聚苯乙烯泡沫为原料制备粉状活性炭的工艺过程。采用化学活化法进行了系列实验,活化时间为120 min,活化温度450~700℃,活化剂用量50%~500%。实验结果表明,采用磷酸作为活化剂,活化剂量∶原料为2∶1~4∶1,产品粉状活性炭性能良好,BET比表面积和亚甲基蓝吸附值分别达到1000 m2/g与10.0 mL/0.1 g以上。产品平均得率在65%以上,远远高于传统原料木材。     

Regeneration of PAC saturated by bisphenol A in PAC/TiO2 combined photocatalysis system

This study investigated a dual function system combining powdered activated carbon (PAC) and TiO₂ for the removal of trace organics together with the in-situ regeneration of PAC. The combined system with PAC adsorption and TiO₂ photo-oxidation for in-situ regeneration of the PAC was studied as a batch process. Bisphenol A (BPA), an endocrine disrupting compound present at low concentration levels, was used as a model compound. When UV light and 0.5 l min^− 1 of oxygen were introduced to the PAC/TiO₂ batch system, the removal of BPA was 2.3 to 3.1 times faster than that of neat TiO₂ oxidation in the pH range of 4 to 10. However, mass transfer of the adsorbed BPA by diffusion from the PAC to oxidation sites on the surface of the TiO₂ was found to be limited because PAC has a strong affinity to adsorb BPA. During in-situ regeneration of PAC by TiO₂ photo-oxidation at pH 7 for 6 h, the removal of BPA from the PAC which was fully saturated with BPA was about 50%. The regeneration of the PAC was improved by increasing the UV-irradiation time (4 h to 12 h) and the light intensity (0.13 mW cm^− 2 to 0.425 mW cm^− 2), but it was not enhanced by increasing temperature, operating at basic conditions, or adding H₂O₂. The results suggest that a process with in-situ regeneration of PAC by TiO₂ oxidation may be feasible.     

Removal of metal ions from aqueous solution by adsorption onto activated carbon cloths: adsorption competition with organic matter

Activated carbon cloths are recent adsorbents whose adsorption properties are well known for monocomponent solutions of organics or metal ions. However, to treat wastewaters with these materials, their performance has to be determined in multicomponent solution. This work studies adsorption competition between metal ions (Cu²⁺, Pb²⁺) and organic matter (benzoic acid). The first part investigates adsorption equilibrium of monocomponent metal ions solutions and shows the dependence of adsorption capacities on adsorbent porosity and metal ions chemical properties (molecular weight, ionic radius and electronegativity). The influence of pH is also demonstrated. The second part focuses on adsorption competition: (1) between both metal ions (a decrease of adsorption capacities is observed, whose value is related to adsorption kinetics of metal ions); (2) between metal ions and organic matter, in solution or adsorbed onto the activated carbon cloth (a strong influence of pH is shown: when benzoic acid is under benzoate form, in both cases adsorption is increased due to the formation of ligands between adsorbed benzoate ions and metals).     

Adsorption of thiram from aqueous solution on activated carbon and sepiolite

Adsorption of thiram on activated carbon and acid-heat treated sepiolite from aqueous solution at 10° C, 20° C, 30° C and 40° C has been studied. The adsorption isotherms may be classified as L type of the Giles classification which suggests that there is no strong competition from the solvent for adsorption sites. The experimental data points have been fitted to the Langmuir equation in order to calculate the adsorption capacities of the solids as well as their surface areas available to the thiram molecules. The removal efficiency (P) has been calculated for both adsorbents resulting that activated carbon is more effective (P = 98–100%) in removing thiram from aqueous solution than acid-heat treated sepiolite (P = 14–52%).     

Removal of thiophenic compounds from liquid fuel by different modified activated carbon cloths

The adsorption behavior of benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT) from n-heptane was investigated onto activated carbon cloth (ACC) and its modified forms at 30 °C in batch condition. ACC was modified by HNO₃, (NH₄)₂S₂O₈, H₂SO₄, HCl and NaOH at ambient temperature. The adsorbents were characterized using nitrogen adsorption/desorption. It was found that the adsorbents are mainly microporous but differ in their surface chemistry, which is related to the effect of oxidizing agent. The adsorption process was studied from both equilibrium and kinetics point of view. The equilibrium experimental data were fitted to the Langmuir, Freundlich and Langmuir-Freundlich by non-linear method. Among the tested adsorbents, the modified ACC with HNO₃ (ACC-HNO₃) had the highest capacity for adsorption of DBT. Kinetic characterization of the adsorption process indicated that the mixed-order and modified pseudo-n-order models can describe the kinetics of adsorption of thiophenic compounds onto ACCs. The ACC and ACC-HNO₃ were used to test the removal efficiency of total sulfur contents (BT, DBT and DMDBT, 150 ppmw for each of them), too. The effect of shaking and ultrasound methods and also temperature and time on the regeneration of saturated ACC-HNO₃ with DBT was studied.     

Adsorption characteristics of toxic chromium(VI) from aqueous media onto nanosized silver nanoparticles-treated activated carbon

The present study reports the use of nanomaterial, e.g. Ag nanoparticles (AgNPs), immobilized activated carbon as an effective solid adsorbent for removal of toxic chromium(VI) from water. Chromium(VI) uptake was found favorable in acidic media at pH ≤ 3. Based on Langmuir model, monolayer adsorption capacities of chromium(VI) found equal 93.5 mg/g. The results fitted well with pseudo second-order and Langmuir models. The mechanism of adsorption was explored using the intra-particle diffusion model and the liquid-film model. Chromatographic separation of chromium(VI) was achieved. The AC-AgNPs was successfully recycled for five successive adsorption–desorption cycles indicating its high reusability.     

活性炭液相吸附脱除二甲基二硫醚

通过椰壳活性炭对模拟硫酸盐松节油进行液相吸附脱硫的研究,考察了活性炭的结构和表面化学对活性炭吸附的影响。通过Gaussian03计算模拟油中各化合物的化学硬度,根据软硬酸碱理论解释表面化学对该吸附过程的影响。同时考察了活性炭吸附过程的热力学性质。结果表明,由于吸附体系中的二甲基二硫醚和莰烯的化学硬度相接近,活性炭表面的含氧官能团的变化对吸附性能影响不大,但活性炭比表面积和孔结构的变化对吸附性能的影响较为明显;等温吸附平衡数据符合Freundlich等温吸附模型,热力学数据显示该活性炭吸附过程是一个放热、混乱度降低的自发物理吸附过程。