Sugarcane bagasse treated with hydrous ferric oxide as a potential adsorbent for the removal of As(V) from aqueous solutions

The mechanism of As(V) removal from aqueous solutions by means of hydrated ferric oxide (HFO)-treated sugarcane bagasse (SCB-HFO) (Saccharum officinarum L.) was investigated. Effects of different parameters, such as pH value, initial arsenic concentration, adsorbent dosage, contact time and ionic strength, on the As(V) adsorption were studied. The adsorption capacity of SCB-HFO for As(V) was found to be 22.1 mg/g under optimum conditions of pH 4, contact time 3 h and temperature 22 °C. Initial As(V) concentration influenced the removal efficiency of SCB-HFO. The desorption of As(V) from the adsorbent was 17% when using 30% HCl and 85% with 1 M NaOH solution. FTIR analyses evidenced two potential binding sites associated with carboxyl and hydroxyl groups which are responsible for As(V) removal. Adsorption, surface precipitation, ion exchange and complexation can be suggested as mechanisms for the As(V) removal from the solution phase onto the surface of SCB-HFO.     

Arsenic adsorption by Fe(III)-loaded open-celled cellulose sponge. Thermodynamic and selectivity aspects

Nowadays there is a great concern on the study of new adsorbent materials for either the removal or fixation of arsenic species because of their high toxicity and the health problems associated to such substances. The present paper reports a basic study of the adsorption of arsenic inorganic species from aqueous solutions using an open-celled cellulose sponge with anion-exchange and chelating properties (Forager Sponge). Consequences of preloading the adsorbentwith Fe(III) to enhance the adsorption selectivity are discussed and compared with the nonloaded adsorbent properties. The interactions of arsenic species with the Fe(III)-loaded adsorbent are accurately determined to clarify the feasibility of an effective remediation of contaminated waters. Arsenate is effectively adsorbed by the nonloaded and the Fe(III)-loaded sponge in the pH range 2-9 (maximum at pH 7), whereas arsenite is only slightly adsorbed by the Fe(III)-loaded sponge in the pH range 5-10 (maximum at pH 9), being that the nonloaded sponge is unable to adsorb As(III). The maximum sorption capacities are 1.83 mmol As(V)/g (pH approximately 4.5) and 0.24 mmol As(lII)/g (pH approximately 9.0) for the Fe(III)-loaded adsorbent. This difference is explained in terms of the different acidic behavior of both arsenic species. The interaction of the arsenic species with the Fe(III) loaded in the sponge is satisfactorily modeled. A 1:1 Fe:As complex is found to be formed for both species. H2AsO4- and H3AsO3 are determined to be adsorbed on Fe(III) with a thermodynamic affinity defined by log K = 2.5 +/- 0.3 and log K = 0.53 +/- 0.07, respectively. As(V) is, thus, found to be more strongly adsorbed than As(III) on the Fe(III) loaded in the sponge. A significant enhancement on As(V) adsorption selectivity by loading Fe(III) in the sponge is observed, and the effectiveness of the Fe(III)-loaded sponge for the As(V) adsorption is demonstrated, even in the presence of high concentrations of interfering anions (chloride, nitrate, sulfate, and phosphate).     

Removal mechanism of As(III) by a novel Fe-Mn binary oxide adsorbent: oxidation and sorption

A novel Fe-Mn binary oxide adsorbent was developed for effective As(III) removal, which is more difficult to remove from drinking water and much more toxic to humans than As(V). The synthetic adsorbent showed a significantly higher As(III) uptake than As(V). The mechanism study is therefore necessary for interpreting such result and understanding the As(III) removal process. A control experiment was conducted to investigate the effect of Na2SO3-treatment on arsenic removal, which can provide useful information on As(III) removal mechanism. The adsorbent was first treated by Na2SO3, which can lower its oxidizing capacity by reductive dissolution of the Mn oxide and then reacted with As(V) or As(III). The results showed that the As(V) uptake was enhanced while the As(III) removal was inhibited after the pretreatment, indicating the important role of manganese dioxide during the As(III) removal. FTIR along with XPS was used to analyze the surface change of the original Fe-Mn adsorbent and the pretreated adsorbent before and after reaction with As(V) or As(III). Change in characteristic surface hydroxyl groups (Fe-OH, 1130, 1048, and 973 cm(-1)) was observed by the FTIR. The determination of arsenic oxidation state on the solid surface after reaction with As(III) revealed that the manganese dioxide instead of the iron oxide oxidized As(III) to As(V). The iron oxide was dominant for adsorbing the formed As(V). An oxidation and sorption mechanism for As(III) removal was developed. The relatively higher As(III) uptake may be attributed to the formation of fresh adsorption sites at the solid surface during As(III) oxidation.     

Adsorption mechanism of arsenic on nanocrystalline titanium dioxide

Arsenate [As(V)] and arsenite [As(III)] interactions at the solid-water interface of nanocrystalline TiO2 were investigated using electrophoretic mobility (EM) measurements, Fourier transform infrared (FTIR) spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and surface complexation modeling. The adsorption of As(V) and As(III) decreased the point of zero charge of TiO2 from 5.8 to 5.2, suggesting the formation of negatively charged inner-sphere surface complexes for both arsenic species. The EXAFS analyses indicate that both As(V) and As(III) form bidentate binuclear surface complexes as evidenced by an average Ti-As(V) bond distance of 3.30 A and Ti-As(III) bond distance of 3.35 A. The FTIR bands caused by vibrations of the adsorbed arsenic species remained at the same energy levels at different pH values. Consequently, the surface complexes on TiO2 maintained the same nonprotonated speciation at pH values from 5 to 10, and the dominant surface species were (TiO)2AsO2- and (TiO)2AsO- for As(V) and As(III), respectively. The surface configurations constrained with the spectroscopic results were formulated in the diffuse layer model to describe the adsorption behavior of As in the pH range between 4 and 12. The study suggests that TiO2 is an effective adsorbent for As removal due to its high surface area and the presence of high affinity surface hydroxyl groups.     

Chromium(III) removal in tannery waste waters using Chinese Reed ( Miscanthus Sinensis), a fast growing plant

Dried Chinese Reed (Miscanthus sinensis) was investigated as adsorbent for the removal of Cr(III) from tannery wastewater. Batch mode adsorption studies were conducted using aqueous solutions of Cr(III). Parameters studied include Cr(III) concentration, agitation time, adsorbent dose and pH. Adsorption followed pseudo-second order kinetic model. Equilibrium adsorption data obeyed both Langmuir and Freundlich isotherms. Langmuir adsorption capacity was found to be 1.85 mg/g. Effects of pH on adsorption and desorption show that both ion exchange and chemisorption are involved in the adsorption process.     

Functionally Modified Cellulose Nanocrystals as an Adsorbent for Anionic Dyes

Cellulose nanocrystal was modified with poly(N,N-diethy-laminomethyl methacrylate) to prepare an adsorbent containing amine groups for removing anionic dyes from waste water. The prepared adsorbent was characterized by Fourier-transform infrared spectrometry (FT-IR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The adsorption was affected by various factors, such as the contact time, adsorbent dosage, dye solution pH value, initial dye concentration, and ionic strength. The results revealed that amine functional groups mainly contribute to the adsorption of azo dyes (AO7). The adsorbent showed pseudo-second-order adsorption kinetics, indicating that the dye molecules were chemisorbed on the adsorbent. The adsorption isotherm was found to fit better with the Langmuir isotherm model than with the Freundlich isotherm model.     

失活乳酸菌去除柑橘汁中链格孢霉毒素TeA工艺优化

柑橘果实易受链格孢霉菌等病原微生物的污染产生并积累链格孢霉毒素,其中细交链孢菌酮酸(tenuazonic acid,TeA)是毒性最强的一种链格孢霉毒素,具有潜在的致癌性和细胞毒性,对消费者的健康和安全构成严重威胁。为降低柑橘汁中TeA含量,本研究利用灭活乳酸菌菌体细胞作为吸附剂,主要研究其吸附去除柑橘汁中TeA的工艺条件。首先通过单因素试验分析灭活乳酸菌菌粉添加量、吸附时间、TeA初始质量浓度和pH值对TeA去除率的影响,然后采用响应面法Box-Behnken设计对吸附去除橙汁中TeA工艺条件进行了优化,得到最佳工艺参数为灭活乳酸菌菌粉添加量1.20g/20mL、吸附时间11.43h、TeA初始质量浓度250μg/L、橙汁pH3.15,在此条件下,TeA去除率为86.98%。同时建立了TeA去除率与各影响因素间的二次多项式回归模型,并对该模型进行了验证,结果表明模型拟合程度高,预测效果好。     

黄麻纤维活性炭对亚甲基蓝和甲基橙溶液的吸附性能研究

以黄麻纤维为原料,采用磷酸活化法制得黄麻纤维活性炭作为吸附剂,以纺织印染加工中较为常用的亚甲基蓝(MB)和甲基橙(MO)染料溶液为吸附质,研究染料溶液初始浓度、活性炭投加量、吸附时间等因素对黄麻纤维活性炭吸附性能的影响。结果表明:随着染料溶液初始浓度的增加,两种染料的去除率逐渐降低,吸附量逐渐增大;随着活性炭投加量的增加和吸附时间的延长,两种染料的去除率和吸附量均呈现逐渐增大的变化规律;水浴温度对两种染料的去除率和吸附量影响都较小;染料溶液pH值对两种染料吸附性能的影响存在较大差异,MB的去除率和吸附量随染料溶液pH值增加而增大,而MO的去除率和吸附量随之减小。     

TiO2-photocatalyzed As(II) oxidation in aqueous suspensions: reaction kinetics and effects of adsorption

Oxidation of arsenite, As(III), to arsenate, As(V), is required for the efficient removal of arsenic by many water treatment technologies. The photocatalyzed oxidation of As(III) on titanium dioxide, TiO2, offers an environmentally benign method for this unit operation. In this study, we explore the efficacy and mechanism of TiO2-photocatalyzed As(III) oxidation at circumneutral pH and over a range of As(III) concentrations approaching those typically encountered in water treatment systems. We focus on the effect of As adsorption on observed rates of photooxidation. Adsorption (in the dark) of both As(III) and As(V) on Degussa P25 TiO2 was examined at pH 6.3 over a range in dissolved arsenic concentrations, [As]diss, of 0.10-89 microM and 0.2 or 0.05 g L(-1) TiO2 for As(III) and As(V), respectively. Adsorption isotherms generally followed the Langmuir-Hinshelwood model with As(III) exhibiting an adsorption maxima of 32 micromol g(-1). As(V) adsorption did not reach a plateau under the experimental conditions examined; the maximum adsorbed concentration observed was 130 micromol g(-1). The extent of As(III) and As(V) adsorption observed at the beginning and end of the kinetic studies was consistent with that observed in the adsorption isotherms. Kinetic studies were performed in batch systems at pH 6.3 with 0.8-42 microM As(III) and 0.05 g L(-1) TiO2; complete oxidation of As(III) was observed within 10-60 min of irradiation at 365 nm. The observed effect of As(III) concentration on reaction kinetics was consistent with surface saturation at higher concentrations. Addition of phosphate at 0.5-10 microM had little effect on either As(III) sorption or its photooxidation rate but did inhibit adsorption of the product As(V). The selective use of hydroxyl radical quenchers and superoxide dismutase demonstrated that superoxide, O2-, plays a major role in the oxidation of As(III) to As(V).     

Removal of arsenic(III) from groundwater by nanoscale zero-valent iron

Nanoscale zero-valent iron (NZVI) was synthesized and tested for the removal of As(III), which is a highly toxic, mobile, and predominant arsenic species in anoxic groundwater. We used SEM-EDX, AFM, and XRD to characterize particle size, surface morphology, and corrosion layers formed on pristine NZVI and As(III)-treated NZVI. AFM results showed that particle size ranged from 1 to 120 nm. XRD and SEM results revealed that NZVI gradually converted to magnetite/maghemite corrosion products mixed with lepidocrocite over 60 d. Arsenic(III) adsorption kinetics were rapid and occurred on a scale of minutes following a pseudo-first-order rate expression with observed reaction rate constants (K(obs)) of 0.07-1.3 min(-1) (at varied NZVI concentration). These values are about 1000x higher than K(obs) literature values for As(III) adsorption on micron size ZVI. Batch experiments were performed to determine the feasibility of NZVI as an adsorbent for As(III) treatment in groundwater as affected by initial As(III) concentration and pH (pH 3-12). The maximum As(III) adsorption capacity in batch experiments calculated by Freundlich adsorption isotherm was 3.5 mg of As(III)/g of NZVI. Laser light scattering (electrophoretic mobility measurement) confirmed NZVI-As(III) inner-sphere surface complexation. The effects of competing anions showed HCO3-, H4SiO4(0), and H2P04(2-) are potential interferences in the As(III) adsorption reaction. Our results suggest that NZVI is a suitable candidate for both in-situ and ex-situ groundwater treatment due to its high reactivity.     

Understanding soluble arsenate removal kinetics by zerovalent iron media

Zerovalent iron filings have been proposed as a filter medium for removing arsenic compounds from potable water supplies. This research investigated the kinetics of arsenate removal from aqueous solutions by zerovalent iron media. Batch experiments were performed to determine the effect of the iron corrosion rate on the rate of As(V) removal. Tafel analyses were used to determine the effect of the As(V) concentration on the rate of iron corrosion in anaerobic solutions. As(V) removal in column reactors packed with iron filings was measured over a 1-year period of continuous operation. Comparison of As(V) removal by freely corroding and cathodically protected iron showed that rates of arsenate removal were dependent on the continuous generation of iron oxide adsorption sites. In addition to adsorption site availability, rates of arsenate removal were also limited by mass transfer associated with As(V) diffusion through iron corrosion products. Steady-state removal rates in the column reactor were up to 10 times faster between the inlet-end and the first sampling port than between the first sampling port and the effluent-end of the column. Faster removal near the influent-end of the column was due to a faster rate of iron oxidation in that region. The presence of 100 microg/L As(V) decreased the iron corrosion rate by up to a factor of 5 compared to a blank electrolyte solution. However, increasing the As(V) concentration from 100 to 20,000 microg/L resulted in no further decrease in the iron corrosion rate. The kinetics of arsenate removal ranged between zeroth- and first-order with respect to the aqueous As(V) concentration. The apparent reaction order was dependent on the availability of adsorption sites and on the aqueous As(V) concentration. X-ray absorption spectroscopy analyses showed the presence of iron metal, magnetite (Fe3O4), an Fe(III) oxide phase, and possibly an Fe(II,III) hydroxide phase in the reacted iron filings. These mixed valent oxide phases are not passivating and permit sustained iron corrosion and continuous generation of new sites for As(V) adsorption.     

Photocatalytic oxidation of arsenic(III): evidence of hydroxyl radicals

Arsenic contamination has been found in the groundwater of several countries. Photocatalysis can rapidly oxidize arsenite (As(III)) to less labile and less toxic arsenate (As(V)), which then can be removed by adsorption onto photocatalyst surfaces. This study investigates the photocatalytic oxidation of As(III) to As(V) as a function of As(III) concentration, pH, catalyst loading, light intensity, dissolved oxygen concentration, type of TiO2 surfaces, and ferric ions to understand the kinetics and the mechanism of As(III) oxidation in the UV/TiO2 system. Photocatalytic oxidation of As(III) to As(V) takes place in minutes and follows zero-order kinetics. Benzoic acid (BA) was used as a hydroxyl radical (.OH) scavenger to provide evidence for the .OH as the main oxidant for oxidation of As(III). The .OH radical was independently generated by nitrate photolysis, and kinetics of As(III) oxidation by the .OH radical was determined. Formation of salicylic acid (SA) from the oxidation of BA by .OH also demonstrates the involvement of .OH in the mechanism of As(III) oxidation. The effect of Fe(III) on As(III) oxidation at different pH values with and without TiO2 under UV light was examined. The results suggest that .OH is the dominant oxidant for As(III) oxidation. Two commercially available TiO2 suspensions, Degussa P25 and Hombikat UV100, were tested for the removal of arsenic through oxidation of As(III) to As(V) followed by adsorption of As(V) onto TiO2 surfaces. Results showed that complete removal of arsenic below the World Health Organization drinking water limit of 10 microg/L could be achieved.     

Removal of color from fruit candy waste by activated carbon adsorption

The research in this paper was aimed at finding a treatment method for recovery of fruit candy (fruit leathers) wastes. Fruit leather wastes were dissolved in water to investigate the efficacy of activated carbon adsorption to remove food colorants, which reduce recycling possibilities. The effects of initial pH (2.5-9), food colorant concentration (10-110 g fruit leather/L) and adsorbent dosage (1-12 g/L) on the adsorption process were investigated. Maximum adsorption was obtained at the original pH value of dissolved fruit candy waste in water. Maximum adsorbent capacities for red, yellow and blue food colorants were 4.4; 11.7 and 2 mg/g at pH 3.5 respectively. Regeneration of food colorant loaded activated carbon can be effected at 400 °C. Cost estimates indicate that red color removal would seem to be an economical proposition, costing about $19/ton fruit candy waste, yellow marginal at $70/ton waste, and blue uneconomical at $245/ton waste.     

Zinc adsorption effects on arsenite oxidation kinetics at the birnessite-water interface

Arsenite is more toxic and mobile than As(V) in soil and sediment environments, and thus it is advantageous to explore factors that enhance oxidation of As(III) to As(V). Previous studies showed that manganese oxides, such as birnessite (delta-MnO2), directly oxidized As(III). However, these studies did not explore the role that cation adsorption has on As(III) oxidation. Accordingly, the effects of adsorbed and nonadsorbed Zn on arsenite (As(III)) oxidation kinetics at the birnessite-water interface were investigated using batch adsorption experiments (0.1 g L(-1); pH 4.5 and 6.0; I= 0.01 M NaCl). Divalent Zn adsorption on synthetic delta-MnO2 in the absence of As(II) increased with increasing pH and caused positive shifts in electrophoretic mobility values at pH 4-6, indirectly suggesting inner-sphere Zn adsorption mechanisms. Arsenite was readily oxidized on birnessite in the absence of Zn. The initial As(III) oxidation rate constant decreased with increasing pH from 4.5 to 6.0 and initial As(III) concentrations from 100 to 300 microM. Similar pH and initial As(III) concentration effects were observed in systems when Zn was present (i.e., presorbed Zn prior to As(III) addition and simultaneously added Zn-As(III) systems), but As(III) oxidation reactions were suppressed compared to the respective control systems. The suppression was more pronounced when Zn was presorbed on the delta-MnO2 surfaces as opposed to added simultaneously with As(III). This study provides further understanding of As(III) oxidation reactions on manganese oxide surfaces under environmentally applicable conditions where metals compete for reactive sites.     

Adsorption and photocatalyzed oxidation of methylated arsenic species in TiO2 suspensions

Monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) are used as herbicides in the agriculture industry. We have demonstrated that MMA and DMA are readily degraded upon TiO2 photocatalysis. DMA is oxidized to MMA as the primary oxidation product, which is subsequently oxidized to inorganic arsenate, As(V). The adsorption of MMA and DMA on Ti02 surface was measured as a function of initial arsenic concentration and solution pH. The pH of the solution influences the adsorption and photocatalytic degradation to a similar degree, due to the speciation of the arsenic substrates and surface charge of TiO2 as a function of pH. The mineralization of MMA and DMA by TiO2 photocatalysis follows the Langmuir-Hinshelwood kinetic model. Addition of tert-butyl alcohol, a hydroxyl radical scavenger, during TiO2 photocatalysis dramatically reduces the rate of degradation, indicating that *OH is the primary oxidant. For dilute solutions, TiO2 may also be applicable as an absorbent for direct removal of a variety of arsenic species, namely As(III), As(V), MMA, and DMA, all of which are strongly adsorbed, thus eliminating the need for a multistep treatment process.     

Arsenic-bicarbonate interaction on goethite particles

The As(V) and As(III) interaction with HCO3 has been studied for goethite systems using a pH and As concentration range that is relevant for field situations. Our study shows that dissolved bicarbonate may act as a competitor for both As(V) and As(III). In our closed systems, the largest effect of bicarbonate occurs at the lowest experimental pH values (pH approximately 6.5), which is related to the pH dependency of the carbonate adsorption process. The experimental data have been modeled with the charge distribution (CD) model. The CD model was separately parametrized for goethite with "single ion" adsorption data of HCO3, As(III), and As(V). The competitive effect of HCO3 on the As(III) and As(V) release could be predicted well. Application of the model shows that the natural As loading of aquifer materials (approximately < 0.01-0.1 micromol/m2 or < 1-5 mg/kg) is at least about > 1-2 orders of magnitude smaller than the As loading based on the competition of As-HCO3 alone. It indicates that another, very prominent competitor, like phosphate and natural organic matter, will strongly contribute to the control of As in natural systems.     

Arsenic removal using mesoporous alumina prepared via a templating method

The health threat of arsenic is well-known, and the U.S. EPA recommends the maximum contaminant level to be 0.01 ppm or less for arsenic in drinking water. Therefore, advanced treatment processes are needed for finished water to meet the required regulations. Adsorption is considered to be a less expensive procedure that is safer to handle than precipitation, ion exchange, and membrane filtration. Activated alumina (AA) is the most commonly used adsorbent for the removal of arsenic from aqueous solutions. However, conventional porous solids including AA have ill-defined pore structures and, typically, low adsorption capacities and act in a kinetically slow manner. An ideal adsorbent should have uniformly accessible pores, an interlinked pore system, a high surface area, and physical and/or chemical stability. To meet this requirement, mesoprous alumina (MA) with a wide surface area (307 m2/g) and uniform pore size (3.5 nm) was prepared, and a spongelike interlinked pore system was developed through a post-hydrolysis method. The resulting MA was insoluble and stable within the range of pH 3-7. The maximum uptake of As(V) by MA was found to be 7 times higher [121 mg of As(V)/g and 47 mg of As(III)/ g] than that of conventional AA, and the kinetics of adsorption were also rapid with complete adsorption in less than 5 h as compared to the conventional AA (about 2 d to reach half of the equilibrium value). A desorption study using sodium hydroxide solutions (0.01-1 M) was conducted, and 0.05 M NaOH was found to be the most suitable desorption agent. More than 85% of the arsenic adsorbed to the MA was desorbed in less than 1 h. Several other activated aluminas with different pore properties were also tested. The results show that the surface area of the adsorbents does not greatly influence on the adsorption capacity. In fact, the key factor is a uniform pore size and an interlinked pore system. These studies show that MA with a wide surface area, uniform pore size, and interlinked pore system can be used as an efficient adsorbent for the removal of arsenic.     

水杨酸改性稻草秸秆对Cu2+的吸附研究

采用水杨酸对稻草秸秆进行改性,研究其对Cu^2+的吸附性能。以制备的吸附剂对Cu^2+的去除率为参考依据,优化吸附剂制备条件,结果显示:稻草秸秆与水杨酸质量比1∶1.5、改性时间120 min、改性温度35℃为最佳制备条件。同时进一步研究吸附剂投加量、吸附温度、吸附时间、溶液初始浓度等因素对吸附效果的影响。当温度为35℃、pH为5.0、吸附时间为90 min时,0.15 g改性吸附剂对15 mg/L的Cu^2+溶液去除率达92.60%。改性稻草秸秆对Cu^2+的吸附过程符合准二级反应动力学方程,用Langmuir和Freundlich吸附等温模型均能描述Cu^2+在改性稻草秸秆上的吸附。     

零价铁/氧化石墨烯复合吸附剂对染料和重金属的吸附性能

针对目前酸性染料染色废水中染料和重金属Cr(Ⅵ)引起的严重环境污染问题,以零价铁(Fe⁰)/氧化石墨烯(GO)复合物作为吸附剂,以分别含有弱酸性蓝AS和Cr(Ⅵ)的水溶液模拟染色废水,探究Fe⁰与GO的质量比、溶液pH值及染料与Cr(Ⅵ)的初始质量浓度对吸附性能的影响,考察Fe⁰/GO吸附剂对酸性染料与Cr(Ⅵ)的吸附机制,研究其吸附热力学与动力学。结果表明：Fe⁰与GO吸附剂在质量比为4∶1时具有最佳吸附效果,弱酸性蓝AS染液初始质量浓度为75 mg/L,温度为30℃,pH值为4.0时,12 h后去除率为85.6%,最大吸附量达到85.6 mg/g; Cr(Ⅵ)溶液初始质量浓度为75 mg/L,温度为30℃,pH值为3.0时,12 h后去除率为95.8%,最大吸附量达到95.8 mg/g; Fe⁰/GO对2种污染物的吸附过程均符合Langmuir模型和准二级动力学模型。     

苹果渣对Cr(Ⅵ)吸附性能的研究

采用静置吸附法,以苹果渣为生物吸附剂,研究其对Cr6+的吸附作用、吸附过程的影响因素、热力学和动力学行为。结果显示：苹果渣对Cr6+的吸附率随其粒径的减小而增大;Cr6+初始质量浓度相同时,吸附率随苹果渣加入量的增加而增大;苹果渣加入量相同时,吸附率总体上随Cr6+初始质量浓度增加呈增大趋势;正交试验得到3个因素对吸附效果的影响程度顺序为吸附温度＞pH值＞吸附时间,最优吸附条件为pH4、吸附温度60℃、吸附时间5h,此条件下吸附率为72.43%;苹果渣对Cr6+的吸附是先快速吸附,吸附时间超过120min后为慢速吸附,用Freundlich吸附等温式能较好地描述其吸附热力学情况,吸附动力学可以用二级动力学模型描述;对于50mg/L的Cr6+溶液,苹果渣为吸附剂时的最佳固液比为8:1000(m/V);苹果渣对中、低质量浓度Cr6+溶液(≤30mg/L)的吸附效果优于活性炭。