Irrigation model of bleached Kraft mill wastewater through volcanic soil as a pollutants attenuation process

An irrigation process through volcanic soil columns was evaluated for bleached Kraft mill effluent pollutants retention. The system was designed to remove color and phenolic compounds and a simple kinetic model for determining the global mass transfer coefficient and the adsorption rate constant was used. The results clearly indicate that the global mass transfer coefficient values (K(c)a) and the adsorption rate constants are higher for the irrigation processes onto acidified soil. This means that the pretreatment of washing the volcanic soil with an acid solution has a positive effect on the adsorption rate for both pollutant groups. The enhanced adsorption capacity is partially explained by the activation of the metal oxides present in the soil matrix during the acid washing process. Increasing the flow rate from 1.5 to 2.5 ml/min yielded higher (K(c)a) values and adsorption rate constants for both pollutant groups. For instance, regarding color adsorption onto acidified soil, there is an increment of 43% in the (K(c)a) value for the experiment with a flow rate of 2.5 ml/min. Increasing the porosity of the column from 0.55 to 0.59, yielded a decrease in the (K(c)a) values for color and phenolic compounds adsorption processes. Onto natural soil for example, these decreases reached 21% and 24%, respectively. Therefore, the (K(c)a) value is dependent on both the liquid-phase velocity (external resistance) and the soil fraction in the column (internal resistance); making forced convection and diffusion to be the main transport mechanisms involved in the adsorption process. Analyzing the adsorption rate constants (K(c)a)/m, phenolic compounds and color adsorption rates onto acidified soil of 2.25 x 10(-6) and 2.62 x 10(-6) l/mg min were achieved for experiment 1. These adsorption rates are comparable with other adsorption systems and adsorbent materials.     

The adsorptive capacity of vapor-phase mercury chloride onto powdered activated carbon derived from waste tires

Injection of powdered activated carbon (PAC) upstream of particulate removal devices (such as electrostatic precipitator and baghouses) has been used effectively to remove hazardous air pollutants, particularly mercury-containing pollutants, emitted from combustors and incinerators. Compared with commercial PACs (CPACs), an alternative PAC derived from waste tires (WPAC) was prepared for this study. The equilibrium adsorptive capacity of mercury chloride (HgCl2) vapor onto the WPAC was further evaluated with a self-designed bench-scale adsorption column system. The adsorption temperatures investigated in the adsorption column were controlled at 25 and 150 degrees C. The superficial velocity and residence time of the flow were 0.01 m/sec and 4 sec, respectively. The adsorption column tests were run under nitrogen gas flow. Experimental results showed that WPAC with higher Brunauer-Emmett-Teller (BET) surface area could adsorb more HgCl2 at room temperature. The equilibrium adsorptive capacity of HgCl2 for WPAC measured in this study was 1.49 x 10(-1) mg HgCl2/g PAC at 25 degrees C with an initial HgCI2 concentration of 25 microg/m3. With the increase of adsorption temperature < or = 150 degrees C, the equilibrium adsorptive capacity of HgCl2 for WPAC was decreased to 1.34 x 10(-1) mg HgCl2/g PAC. Furthermore, WPAC with higher sulfur contents could adsorb even more HgCl2 because of the reactions between sulfur and Hg2+ at 150 degrees C. It was demonstrated that the mechanisms for adsorbing HgCl2 onto WPAC were physical adsorption and chemisorption at 25 and 150 degrees C, respectively. Experimental results also indicated that the apparent overall driving force model appeared to have the good correlation with correlation coefficients (r) > 0.998 for HgCl2 adsorption at 25 and 150 degrees C. Moreover, the equilibrium adsorptive capacity of HgCl2 for virgin WPAC was similar to that for CPAC at 25 degrees C, whereas it was slightly higher for sulfurized WPAC than for CPAC at 150 degrees C.     

Biomass-derived materials in the remediation of heavy-metal contaminated water: removal of Cadmium(II) and copper(II) from aqueous solutions

Manganese-coated activated carbon (MCAC) and activated carbon were used in batch experiments for the removal of cadmium(II) and copper(II). Results showed that uptake of Cd(II) and Cu(II) was unaffected by increases in pH (3.0 to 8.5) or concentration (1 to 20 mg/L). Increased ionic strength (from 0.001 to 1 M NaNO3), however, significantly affected the uptake of Cd(II); adsorption of Cu(II) was not affected. Freundlich adsorption isotherm results indicated that MCAC possessed higher sorption capacity than activated carbon. Second-order rate constants were found to be 0.0386 for activated carbon and 0.0633 g/mg x min for MCAC for Cd(II) and 0.0774 for AC and 0.1223 g/mg x min for MCAC for Cu(II). Column experiments showed that maximum sorption capacity of MCAC was 39.48 mg/g for Cu(II) and 12.21 mg/g for Cd(II).     

给水处理厂铁铝泥对正磷酸盐的吸附效果

通过批量实验和柱状实验并结合磷的分级提取探究了给水处理厂废弃铁铝泥(ferric-alum water treatment re-siduals,FARs)吸附正磷酸盐的效果。批量实验结果表明,Langmuir和Freundlich方程均能较好地描述FARs对磷的等温吸附过程,且当pH从5增至9时,FARs磷的饱和吸附量从41.68 mg/g减小到17.08 mg/g。pH越低,磷与FARs的结合能力越强。柱状实验结果表明,FARs具有显著的磷吸附能力,在运行的89 d里,磷的去除率保持在80%以上。出水pH与进水相比略有增加,但增加量不会对地表水体造成影响。磷的分级提取结果进一步说明,被吸附的磷主要以释磷风险小的铁铝结合态存在。综合实验结果表明,FARs可以作为高效磷吸附剂应用于地表水除磷。     

Sorption of Cr(VI) from dilute solutions and wastewater by live and pretreated biomass of Aspergillus flavus

Sorption of Cr(VI) was carried out from dilute solutions using live and pretreated biomass in a batch mode. Effects of agitation time, adsorbent dosage and pH were examined. The autoclaved biomass that showed maximum adsorption capacity (Q(0)=0.335 mg g(-1)) was used as an adsorbent in column studies. The optimized flow rate of 2.5 ml min(-1) and bed height 10 cm were used to determine the effect of metal ion concentration on removal of Cr(VI). Applying the BDST model to calculate the adsorption capacity (N(0)) of column, which showed 4.56 x 10(-5), 7.28 x 10(-5), 6.89 x 10(-5), 3.07 x 10(-5), 2.80 x 10(-5)mg g(-1) for 4, 8, 12, 16 and 20 mg dm(-3) of Cr(VI), respectively. Batch sorption proved to be more efficient than the column sorption and hence batch sorption was used to remove Cr(VI) from a textile dyeing industry wastewater. The phytotoxic effect of treated and untreated wastewater was studied against Zea mays. Toxicity was reduced by 50% in the treated effluent.     

Cellulose supported layered double hydroxides for the adsorption of fluoride from aqueous solution

Cellulose supported layered double hydroxides (CSLDHs) were synthesized and tested for adsorption of fluoride in aqueous medium. Three samples of cellulose supported LDHs were synthesized by varying the LDH loading on cellulose. The raw cellulose, unsupported LDH and cellulose supported LDHs were characterized by XRD, SEM and BET surface area. Batch adsorption as well as fixed-bed column experiments were performed for determining the fluoride adsorption characteristics of CSLDHs. The fluoride adsorption properties of CSLDHs were found to be superior to that of reported adsorbents, including activated alumina and carbon nanotubes. Defluoridation capacity of the CSLDHs was 2-4 times higher than that of unsupported LDH. The cellulose supported LDH, CSLDH-50, having an LDH loading of 27% showed maximum fluoride uptake capacity (5.29 mg g(-1) of CSLDH, 25.18 mg g(-1) of LDH) in fixed-bed column study.     

Removal of metal ions and humic acid from water by iron-coated filter media

Iron oxide is an excellent, regenerable adsorbent, and often controls free metals through adsorption reaction. The utilization of heating process for coating iron oxide on sand surface allowed the media to be used in a packed column. Iron-coated sand was investigated for adsorbing metal ions and natural organic matter from water by batch and column experiments. Chemical analysis (energy dispersive analysis of X-ray, EDAX) was used for characterizing the copper and lead adsorption sites on iron-coated sand. From the batch experiment results, the copper and lead ions could be removed simultaneously by the iron-coated sand in the competition adsorption system. The interaction between copper, lead ions and iron oxide on sand surface was primarily the chemical bonds. The maximum adsorption capacities of iron-coated sand for copper and lead were 0.259 mg Cu/g-sand and 1.211 mg Pb/g-sand, respectively. The presence of humic acid led to increase the adsorption of copper and lead. Results from column experiments indicated that the copper ions, lead ions and humic acid could be removed completely before the breakpoint. Consequently, the iron-coated sand may be applied for the adsorption/filtration of metal ions and natural organic matters from water.     

Adsorption of methabenzthiazuron on six allophanic and nonallophanic soils: effect of organic matter amendment

This article reports on methabenzthiazuron [1-(1,3-benzothiazol-2-yl)-1,3-dimethylurea] (MBT) adsorption process on six agricultural allophanic and nonallophanic soils. The effect of amendment with exogenous organic matter was also studied. Adsorption kinetic fits an hyperbolic model. MBT adsorption reached an apparent equilibrium within 2 h and followed a second-order reaction. The maximum adsorbed amounts for natural soils ranged from 32 to 145 microg g(-1). Rate constants were considered relatively low (0.27-1.5 x 10(-4) [microg g(-1)](1-n) s-1); the slow process was attributed to a combined effect of difussion and adsorption. MBT adsorption fits the Freundlich model with r values > or =0.998 at P < or = 0.001 significance levels. Kf and Freundlich exponents (l/n) ranged from 5.3 to 82.1 cm3 g(-1) and from 0.66 to 0.73, respectively. Kf values for soils with a low organic matter content were lower than that obtained from the only typical allophanic soil derived from volcanic ash under study. Lineal regression analysis between Kf and organic matter content of nonallophanic soils gave a correlation coefficient of 0.980 (P = 0.02). Dispersion of Kd values together with close values of K(OM) indicate that organic matter (OM) was the principal component responsible for MBT adsorption in unamended soils. Addition of peat decreased soil pH and increased adsorption capacity for allophanic and nonallophanic soils. Kinetic experiments showed enhancements of Xmax values and lower rate constants.     

MWNTs及MWNTs/TiO_2对水中1,2,3-三氯苯的吸附特性研究

采用批量平衡实验,对比研究了多壁碳纳米管（MWNTs）及多壁碳纳米管/二氧化钛复合材料（MWNTs/TiO2）对水中1,2,3-三氯苯的吸附特性。结果表明,在相同条件下,MWNTs及MWNTs/TiO2对1,2,3-三氯苯（1,2,3-TCB）的最大吸附量分别为71.8 mg/g和3.05 mg/g,pH值在2~11之间变化时,两者的吸附均不受pH值变化的影响。2种吸附剂的吸附过程均符合拟二级动力学方程,但MWNTs/TiO2对1,2,3-TCB的吸附速率常数为0.4159 g/（mg.m in）,约为MWNTs的50倍左右,说明MWNTs/TiO2具有更强的吸附驱动力。1,2,3-TCB在2种吸附剂上的吸附过程均可用Freund lich吸附等温线来描述,其热力学参数吉布斯自由能△G0均为负、标准焓变△H0与熵变△S0均为正表明,MWNTs及MWNTs/TiO2吸附1,2,3-TCB过程为自发吸热反应。与MWNTs相比,MWNTs/TiO2具有可光催化再生的优点,能用于被污染水体的原位修复。     

MWNTs及MWNTs/TiO2对水中1,2,3-三氯苯的吸附特性研究

采用批量平衡实验,对比研究了多壁碳纳米管（MWNTs）及多壁碳纳米管/二氧化钛复合材料（MWNTs/TiO₂）对水中1,2,3-三氯苯的吸附特性。结果表明,在相同条件下,MWNTs及MWNTs/TiO₂对1,2,3-三氯苯（1,2,3-TCB）的最大吸附量分别为71.8 mg/g和3.05 mg/g,pH值在2~11之间变化时,两者的吸附均不受pH值变化的影响。2种吸附剂的吸附过程均符合拟二级动力学方程,但MWNTs/TiO₂对1,2,3-TCB的吸附速率常数为0.4159 g/(mg·min),约为MWNTs的50倍左右,说明MWNTs/TiO₂具有更强的吸附驱动力。1,2,3-TCB在2种吸附剂上的吸附过程均可用Freundlich吸附等温线来描述,其热力学参数吉布斯自由能△G⁰均为负、标准焓变△H⁰与熵变△S⁰均为正表明,MWNTs及MWNTs/TiO₂吸附1,2,3-TCB过程为自发吸热反应。与MWNTs相比,MWNTs/TiO₂具有可光催化再生的优点,能用于被污染水体的原位修复。     

污泥含炭吸附剂对挥发性有机废气吸附实验研究

研究了污泥含炭吸附剂对挥发性有机污染物的吸附特性。结果表明,污泥含炭吸附剂对苯系物的吸附为典型的物理吸附,其吸附甲苯等温线的类型系优惠型吸附等温线,表明具有良好的吸附能力;在吸附反应温度为20℃,气体流量为500 mL/m in(停留时间为0.424 s),甲苯浓度为2 700 mg/m3时,甲苯的饱和吸附容量为150.0 mg/g;同时,研究表明污泥含炭吸附剂对苯系物的饱和吸附容量和吸附强弱次序为二甲苯甲苯苯。结果表明污泥含炭吸附剂适合对中低浓度有机废气的吸附净化。     

非固定化和固定化啤酒酵母对Cd^2＋和Cu^2＋的吸附特性研究

对比了不同吸附剂对重金属的吸附效果,同时研究了啤酒酵母的固定化方法、菌体用量对吸附效果的影响、非同定化和固定化啤酒酵母吸附热力学特性。研究结果表明,非固定化死啤酒酵母对Cd^2＋的单位菌体吸附量是常用吸附剂活性炭的3倍;由1：3的海藻酸钠与碱处理啤酒酵母（w／w）制得的固定化颗粒吸附效果最好;菌体用量的增加会降低单位菌体对重金属的吸附量;啤酒酵母对重金属的吸附位点有限,Cd^2＋的实际最大吸附量为13．95mg／g,Cu^2＋为7．67μg／g。非固定化和固定化啤酒酵母对Cu^2＋和Cd^2＋的等温吸附过程均可用Linear方程、Langmuir方程和Freundlich方程来进行拟合,但非同定化啤酒酵母以Langmuir方程最优,其拟合计算的最大吸附量qmzxCd和qmxxCu分别为13．96mg／g和8．01mg／g;固定化啤酒酵母以Freundlich方程最优,实际最大吸附量Cd为75．41mg／g,Cu为66．58mg／g。     

The Adsorptive Capacity of Vapor-Phase Mercury Chloride onto Powdered Activated Carbon Derived from Waste Tires

Abstract

Injection of powdered activated carbon (PAC) upstream of particulate removal devices (such as electrostatic precipitator and baghouses) has been used effectively to remove hazardous air pollutants, particularly mercury-containing pollutants, emitted from combustors and incinerators. Compared with commercial PACs (CPACs), an alternative PAC derived from waste tires (WPAC) was prepared for this study. The equilibrium adsorptive capacity of mercury chloride (HgCl₂) vapor onto the WPAC was further evaluated with a self-designed bench-scale adsorption column system. The adsorption temperatures investigated in the adsorption column were controlled at 25 and 150 °C. The superficial velocity and residence time of the flow were 0.01 m/sec and 4 sec, respectively. The adsorption column tests were run under nitrogen gas flow. Experimental results showed that WPAC with higher Brunauer–Emmett–Teller (BET) surface area could adsorb more HgCl₂ at room temperature. The equilibrium adsorptive capacity of HgCl₂ for WPAC measured in this study was 1.49 × 10^?1 mg HgCl₂/g PAC at 25 °C with an initial HgCl₂ concentration of 25 μg/m³. With the increase of adsorption temperature ≤150 °C, the equilibrium adsorptive capacity of HgCl₂ for WPAC was decreased to 1.×34 10^?1 mg HgCl₂/g PA≤C. Furthermore,WPAC with higher sulfur contents could adsorb even more HgCl₂ because of the reactions between sulfur and Hg²⁺ at 150 °C. It was demonstrated that the mechanisms for adsorbing HgCl₂ onto WPAC were physical adsorption and chemisorption at 25 and 150 °C, respectively. Experimental results also indicated that the apparent overall driving force model appeared to have the good correlation with correlation coefficients (r) >0.998 for HgCl₂ adsorption at 25 and 150 °C. Moreover, the equilibrium adsorptive capacity of HgCl₂ for virgin WPAC was similar to that for CPAC at 25 °C, whereas it was slightly higher for sulfurized WPAC than for CPAC at 150 °C.     

Development of a scalable model for predicting arsenic transport coupled with oxidation and adsorption reactions

Understanding the fundamentals of arsenic adsorption and oxidation reactions is critical for predicting its transport dynamics in groundwater systems. We completed batch experiments to study the interactions of arsenic with a common MnO2(s) mineral, pyrolusite. The reaction kinetics and adsorption isotherm developed from the batch experiments were integrated into a scalable reactive transport model to facilitate column-scale transport predictions. We then completed a set of column experiments to test the predictive capability of the reactive transport model. Our batch results indicated that the commonly used pseudo-first order kinetics for As(III) oxidation reaction neglects the scaling effects with respect to the MnO2(s) concentration. A second order kinetic equation that explicitly includes MnO2(s) concentration dependence is a more appropriate kinetic model to describe arsenic oxidation by MnO2(s) minerals. The arsenic adsorption reaction follows the Langmuir isotherm with the adsorption capacity of 0.053micromol of As(V)/g of MnO2(s) at the tested conditions. The knowledge gained from the batch experiments was used to develop a conceptual model for describing arsenic reactive transport at a column scale. The proposed conceptual model was integrated within a reactive transport code that accurately predicted the breakthrough profiles observed in multiple column experiments. The kinetic and adsorption process details obtained from the batch experiments were valuable data for scaling to predict the column-scale reactive transport of arsenic in MnO2(s)-containing sand columns.     

Impact of sewage sludge spreading on nickel mobility in a calcareous soil: adsorption–desorption through column experiments

A soil column adsorption–desorption study was performed on an agricultural calcareous soil to determine the impact of sewage sludge spreading on nickel mobility. Ni adsorption experiments were followed by desorption tests involving the following liquid extractants: water, calcium (100 mg/L), oxalic acid (525 mg/L equivalent to 100 mg carbon/L), and sludge extracts (0.5 and 2.5 g/L). Desorption tests were also conducted after sewage sludge spreading at three application rates (30, 75, and 150 t/ha). According to the breakthrough curve, Ni adsorption was irreversible and occurred mainly through interactions with calcite surface sites. Nickel desorption from the soil column was promoted in presence of significant dissolved organic carbon (DOC) concentration as observed with oxalic acid elution and sludge extract at 2.5 g/L. In sludge-amended soil columns, the maximum Ni levels occurred in first pore volumes, and they were positively correlated to the sludge application rate. The presence of DOC in leaching waters was the main factor controlling Ni desorption from the sludge-amended soil columns. This finding implies that DOC generated by sludge applied on calcareous soils might facilitate the leaching of Ni due to the formation of soluble Ni–organic complexes. Thus, sludge application can have potential environmental impacts in calcareous soils, since it promotes nickel transport by decreasing Ni retention by soil components.     

Adsorption of arsenic(V) by activated carbon prepared from oat hulls

The efficiency of self-manufactured activated carbon (AC) produced from oat hulls in adsorbing arsenic(V) was tested in a batch reactor. The results indicated that the adsorptive capacity of AC was affected by initial pH value, with adsorption capacity decreasing from 3.09 to 1.57 mg As g(-1) AC when the initial pH values increased from 5 to 8. A modified linear driving force model conjugated with a Langmuir isotherm was created to describe the study's kinetics. The test results show that rapid adsorption and slow adsorption exist simultaneously when AC is used to remove arsenic(V).     

SDS改性沸石吸附结晶紫简

以表面活性剂十二烷基硫酸钠（SDS）对沸石进行改性,改性后的沸石对结晶紫溶液进行吸附,以紫外可见分光光度计分析最佳吸附条件。实验结果表明,在30℃,SDS改性沸石投入量为0.25 g;吸附平衡时间为1 h;pH为8的条件下,对含50 mg/L结晶紫染料的去除率可达到92.6%,吸附量达到4.63 mg/g。SDS改性沸石吸附结晶紫的等温吸附曲线与Henry型和Freundlich型均拟合较好。热力学参数计算结果表明,吸附符合自发吸热过程。     

SDS改性沸石吸附结晶紫

以表面活性剂十二烷基硫酸钠（SDS）对沸石进行改性,改性后的沸石对结晶紫溶液进行吸附,以紫外可见分光光度计分析最佳吸附条件。实验结果表明,在30℃,SDS改性沸石投入量为0．25g;吸附平衡时间为1h;pH为8的条件下,对含50mg／L结晶紫染料的去除率可达到92．6％,吸附量达到4．63mg／g。SDS改性沸石吸附结晶紫的等温吸附曲线与Henry型和Freundlich型均拟合较好。热力学参数计算结果表明,吸附符合自发吸热过程。     

Sorptive behavior of sorgoleone in ultisol in two solvent systems and determination of its lipophilicity

Sorgoleone (SGL) exuded by sorghum roots inhibits the development of some weeds. Due to its high hydrophobicity, it is expected that SGL presents low soil mobility and limited allelopathic activity in the field. This work aims to evaluate the sorptivity of sorgoleone in octanol-water and in soil under two solvent systems. The two solvent systems were methanol:water (60:40) (MeOH:H2O) and pure methanol (MeOH). These two solvent systems promote different conditions for SGL solubility. Treatments were arranged in a 2 x 6 factorial (solvent systems x equilibrium concentrations in the solution (EC)). For each solvent, the sorption was achieved by shaking 500 mg of soil with 10 ml of 0, 5, 10, 15, 25, 40, and 60 mg L-1 of SGL solution, during 24 h. After centrifugation, the supernatant was filtered and the SGL concentration was determined by high performance liquid chromatography (HPLC). Data of sorbed amount of SGL were submitted to variance analysis, using a hierarchic factorial model. The data of sorbed amount (x/m) and equilibrium concentration (C) were fitted to the linear (x/m = a + KdC) and to the Freundlich (x/m = KfC1/n) models. The isotherm obtained for the MeOH:H2O system presented linear shape, whereas for the MeOH system a two subsequent linear isotherm was fitted. Sorgoleone is a highly hydrophobic compound, presenting a log Kow of 6.1. The sorption of sorgoleone to the soil was very high. The organic environment stimulated the sorgoleone sorption to the soil.     

Biodegradation of trace gases in simulated landfill soil cover systems

The attenuation of methane and seven volatile organic compounds (VOCs) was investigated in a dynamic methane and oxygen counter gradient system simulating a landfill soil cover. The VOCs investigated were: Tetrachloromethane (TeCM), trichloromethane (TCM), dichloromethane (DCM), trichloroethylene (TCE), vinyl chloride (VC), benzene, and toluene. Soil was sampled at Skellingsted landfill, Denmark. The soil columns showed a high capacity for methane oxidation, with oxidation rates up to 184 g/m2/d corresponding to a 77% reduction of inlet methane. Maximal methane oxidation occurred at 15-20 cm depth, in the upper part of the column where there were overlapping gradients of methane and oxygen. All the chlorinated hydrocarbons were degraded in the active soil columns with removal efficiencies higher than 57%. Soil gas concentration profiles indicated that the removal of the fully chlorinated compound TeCM was because of anaerobic degradation, whereas the degradation of lower chlorinated compounds like VC and DCM was located in the upper oxic part of the column. Benzene and toluene were also removed in the active column. This study demonstrates the complexity of landfill soil cover systems and shows that both anaerobic and aerobic bacteria may play an important role in reducing the emission of trace components into the atmosphere.