Removal of methylene blue from aqueous solution using wine-processing waste sludge

Dye wastewaters usually contain toxins and high chroma, making them difficult to treat with biological methods. The adsorption process plays an important role in removing dyes from wastewaters. This study aimed to explore the methylene blue (MB) adsorption mechanism by wine-processing waste sludge (WPWS). The WPWS contains a high cation-exchange capacity (64.2 cmol(c) kg(-1)) and organic matter (52.8%). The parameters affecting MB adsorption included pH, initial concentration of MB, reaction temperature, particle size and dosage of WPWS. The WPWS adsorption isotherms of MB were only well described by Langmuir adsorption isotherm. The maximum adsorption capacity (Q(m)) of MB was 285.7 mg g(-1) at 25 °C. The activation energy determined by Arrhenius equation is 29.995 kJ mol(-1). Under steady-state reaction conditions, the Gibb free energy (ΔG°) ranged from -24.607 to -27.092 kJ mol(-1) and ΔH° was -8.926 kJ mol(-1), indicating that lower reaction temperature would favor MB adsorption. Therefore, MB adsorption by WPWS was a spontaneous, exothermic and physisorption reaction.     

Adsorption kinetics, isotherms and thermodynamics of atrazine removal using a banana peel based sorbent

Atrazine removal from water by treated banana peels was studied. The effect of pH, contact time, initial atrazine concentration, and temperature were investigated. Batch experiments demonstrated that 15 g L(-1) adsorbent dosage removed 90-99% of atrazine from 1-150 ppm aqueous solutions. The removal was both pH and temperature dependent with the most atrazine removed between pH 7 and 8.2 and increased with increasing temperature. Equilibrium data fitted well to the Langmuir and Redlich-Peterson models in the concentration and temperature ranges investigated, with a maximum adsorption capacity of 14 mg g(-1). Simple mass transfer models were applied to the experimental data to examine the adsorption mechanism and it was found that both external mass transfer and intraparticle diffusion played important roles in the adsorption mechanisms. The enthalpy of atrazine adsorption was evaluated to be 67.8 ± 6.3 kJ mol(-l) with a Gibbs free energy of -5.7 ± 1.2 kJ mol(-1).     

Equilibrium, kinetic and thermodynamic studies of mercury adsorption on almond shell

The application of almond shell as a low cost natural adsorbent to remove Hg(2+) from aqueous solution was investigated. Batch experiments were carried out to evaluate the adsorption capacity of the material. The chemical and physical parameters such as pH, sorbent amount, initial ion concentration, and contact time were optimized for the maximum uptake of mercury onto the solid surface. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models, and the experimental data were found to fit the Langmuir model rather than the Freundlich. The maximum adsorption capacity obtained from the Langmuir isotherm was 135.13 mg/g. A kinetic study was carried out with pseudo-first-order and pseudo-second-order reaction equations and it was found that the Hg(2+) uptake process followed the pseudo-second-order rate expression. The thermodynamic values, ΔG(0), ΔH(0) and ΔS(0), indicated that adsorption was an endothermic and spontaneous process. The potential of this material for mercury elimination was demonstrated by efficient Hg(2+) removal from a synthetic effluent.     

Preparation and characterization of CTAB-HACC bentonite and its ability to adsorb phenol from aqueous solution

A novel type of adsorbent was prepared by modifying bentonite with N-2-hydroxypropyl trimethyl ammonium chloride chitosan (HACC) with cetyl trimethylammonium bromide (CTAB). The adsorbent was named CTAB-HACC bentonite. Its characteristics were investigated using thermogravimetric, Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction. The adsorption of phenol onto CTAB-HACC bentonite was evaluated by changing various parameters, such as contact time, adsorbent dosage, initial pH of the solution, and temperature. The maximum adsorption was observed at pH 12. Adsorption of phenol on CTAB-HACC bentonite favored at lower temperature and established the equilibrium in 30 min. The adsorption efficiency reached 82.1%, and the adsorption capacity was 7.12 mg/g from the phenol solution with a concentration of 500 mg/L at pH 12.0 and 20 degrees C.     

Studies on the adsorption of sulfo-group-containing aromatics by chitosan-β-cyclodextrin

Chitosan-β-cyclodextrin (CTS-CD) prepared through a crosslinking reaction between chitosan and β-cyclodextrin was employed to adsorb the three following sulfo-group-containing aromatics: disodium 2-naphthol-3,6-disulfonate (R salt), 2-naphthalene sulfonic acid (NSA), and sodium dodecylbenzene sulfonate (SDBS). At 318 K, the saturated adsorption capacity of CTS-CD for R salt, NSA, and SDBS was 431, 416, and 376 mg/g, respectively. The experimental data fitted the second-order model well and the rate constant of the adsorption increased with the temperature increment. The values of apparent activation energy for R salt, NSA, and SDBS were calculated as 33.2, 34.2, and 16.8 kJ/mol respectively. The isothermal adsorption was found following the Langmuir adsorption equation. The negative values of ΔG and the positive values of ΔH indicated that the adsorption process was spontaneous and exothermic.     

甘蔗渣对中性红的吸附性能的实验研究

对甘蔗渣进行了吸附去除印染废水中的中性红模拟实验研究。考察了甘蔗粉用量、pH、吸附时间、中性红初始浓度和温度等因素对吸附效果的影响,探究了其吸附动力学及吸附规律。结果表明,甘蔗粉用量、pH、吸附时间和中性红初始浓度、温度等因素对甘蔗粉吸附水中中性红有显著影响。适宜的吸附条件为:甘蔗粉用量0.6g/100mL,pH6.0～7.0,吸附时间60min,初始浓度100mg/L,温度30℃。在该条件下,中性红的去除率达91%以上。甘蔗粉对中性红的吸附过程可以用Langmuir、Temkin等温吸附方程和二级吸附速率方程进行很好的描述,主要表现为物理吸附。     

Biosorption of As(V) from aqueous solutions by living cells of Bacillus cereus

In this work, the biosorption of As(V) from aqueous solutions by living cells of Bacillus cereus has been reported. The batch biosorption experiments were conducted with respect to biosorbent dosage 0.5 to 15 g/L, pH 2 to 9, contact time 5 to 90 min, initial concentration 1 to 10 mg/L and temperature 10 to 40 °C. The maximum biosorption capacity of B. cereus for As(V) was found to be 30.04 at pH 7.0, at optimum conditions of contact time of 30 min, biomass dosage of 6 g/L, and temperature of 30 ± 2 °C. Biosorption data were fitted to linearly transformed Langmuir isotherms with R(2) (correlation coefficient) >0.99. Bacillus cereus cell surface was characterized using AFM and FTIR. The metal ions were desorbed from B. cereus using both 1 M HCl and 1 M HNO(3). The pseudo-second-order model was successfully applied to predict the rate constant of biosorption.     

Use of sesame stalk biomass for the removal of Ni(II) and Zn(II) from aqueous solutions

In this study an agricultural residue, sesame stalk, was evaluated for the removal of Ni(II) and Zn(II) metal ions from aqueous solutions. Biosorption studies were carried out at different pH, biosorbent dosage, initial metal ion concentrations, contact time, and solution temperature to determine the optimum conditions. The experimental data were modeled by Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models. Langmuir model resulted in the best fit of the biosorption data. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data and to evaluate rate constants. The best correlation was provided by the second-order kinetic model. The thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated for predicting the nature of adsorption. The experimental results showed that sesame stalk can be used as an effective and low-cost biosorbent precursor for the removal of heavy metal ions from aqueous solutions.     

Photocatalytic removal of cyanide with illuminated TiO(2)

Effects of TiO(2) dosage, pH and initial cyanide concentration on the removal efficiency of cyanide from aqueous solutions with illuminated TiO(2) have been investigated. Adsorption and oxidation were recognized as significant processes for the elimination of cyanide. From the Langmuir isotherm, the maximum adsorption capacity was determined as 17.24 mg/g at pH 7. Adsorbed amount of cyanide slightly increased as the TiO(2) dosage increased. However, as no significant increase was observed above 1 g/L TiO(2), an optimum TiO(2) dosage was determined as 1 g/L. Photocatalytic oxidation efficiency of cyanide was greatly affected by the solution pH. It increased as the solution pH decreased. The photocatalytic oxidation efficiency after 120 min was 80.4% at pH 3 while it was only 20.4% at pH 11. Photocatalytic oxidation of cyanide was well described by the second-order kinetics. Photocatalytic reaction with illuminated TiO(2) can be effectively applied to treat industrial wastewater contaminated with cyanide.     

含锌重金属废水藻类吸附处理技术

以小球藻为吸附剂,研究藻类吸附剂对重金属废水中Zn2+的吸附过程,分析吸附时间、温度、pH值、Zn2+起始浓度以及预处理过程等因素对小球藻吸附Zn2+性能的影响。结果表明:预处理能提高小球藻的吸附性能,其吸附过程符合Langmuir吸附特征,对废水的pH值适应范围广。对于ρ(Zn2+)=100 mg/L的重金属废水经小球藻一次处理,去除率达到98%。小球藻吸附处理废水中Zn2+的较佳工艺条件为pH值6.5、温度25℃、吸附时间60 min、小球藻用量2 g/L。     

铝污泥吸附水中磷的影响因素及响应面法优化

为提高铝污泥的利用效率,将其更好地应用于富营养化水体的修复之中,以给水厂脱水铝污泥为吸附材料对水中的磷进行吸附,考察铝污泥投加量、铝污泥颗粒粒径、体系pH、水样磷浓度对吸附效果的影响。拟合了等温吸附方程,并借助响应面分析中的BBD(Box-Behnken Design)模型确定吸附时间、pH和铝污泥投加量这3种因素对吸附反应影响的显著性及交互作用的强弱,同时利用此模型对实验条件进行优化。结果表明:①上述4种因素均对吸附过程有所影响,Langmuir等温吸附方程拟合效果较好,铝污泥对磷的理论饱和吸附量为1.487 mg/g(温度298 K)。②铝污泥投加量对吸附的影响最为显著,pH和反应时间产生的交互作用最强。③当水体中磷浓度为10 mg/L时,其最佳工艺条件为铝污泥投加量12 g/L、pH=4.5及反应时间48 h,最大去除率为92.38%。     

Effects of oxidant concentration and temperature on decolorization of azo dye: comparisons of UV/Fenton and UV/Fenton-like systems

This study applies photo-Fenton and photo-Fenton-like systems to decolorize C.I. Reactive Red 2 (RR2). The oxidants were H(2)O(2) and Na(2)S(2)O(8); Fe(2+), Fe(3+), and Co(2+) were used to activate these two oxidants. The effects of oxidant concentration (0.3-2 mmol/L) and temperature (25-55 °C) on decolorization efficiency of the photo-Fenton and photo-Fenton-like systems were determined. The decolorization rate constants (k) of RR2 in the tested systems are consistent with pseudo-first-order kinetics. The rate constant increased as oxidant concentration and temperature increased. Activation energies of RR2 decolorization in the UV/H(2)O(2)/Fe(2+), UV/H(2)O(2)/Fe(3+), UV/Na(2)S(2)O(8)/Fe(2+) and UV/Na(2)S(2)O(8)/Fe(3+) systems were 32.20, 39.54, 35.54, and 51.75 kJ/mol, respectively.     

Removal of hexavalent chromium from wastewater by Fe0-nanoparticles-chitosan composite beads: characterization, kinetics and thermodynamics

Fe0-nanoparticles-chitosan composite beads (CS-NZVI beads) were prepared and used to remove hexavalent chromium (Cr (VI)) from wastewater. Characterization with a scanning electron microscopy (SEM) demonstrated that with the increase of the concentration of CS from 5.0 to 20.0 g/L and NaOH from 0.5 to 2.0 mol/L, the average aperture size of the CS-NZVI beads decreased from 26.8 to 10.6 μm and 42.6 to 0.8 μm, respectively. Batch experiments revealed that the removal of Cr (VI) using CS-NZVI beads was consistent with pseudo first-order reaction kinetics. The rate constant increased with increasing NZVI dosage but decreased with the increase in pH values. The Freundlich isotherm described the adsorption process better, suggesting that the CS-NZVI beads were heterogeneous in the surface properties. At equilibrium qmax was 35.97 mg/g. The thermodynamics study suggested that Cr (VI) removal by CS-NZVI beads was an endothermic and spontaneous process, reflecting good affinity of the sorbent for Cr (VI) ions and increasing randomness at the solid-solution interface during the adsorption process. This result will be very useful to understand the effects of NZVI on heavy metal Cr (VI) removal from wastewater in the successful application.     

花生壳对模拟废水中Cr(Ⅵ)的动态吸附特性研究

采用废弃花生壳对质量浓度为20 mg/L的Cr(Ⅵ)模拟水样进行动态吸附实验研究。结果表明:在室温条件下,用粒径为1.6～2.5 mm花生壳作吸附剂,用量为5.0 g,介质pH值为1.0,流量为3 mL/min,吸附后水样中Cr(Ⅵ)的去除率可以达到99.08%,Cr(Ⅵ)质量浓度为0.184 mg/L,满足GB 8978—1996《污水综合排放标准》的标准。对模型的拟合结果表明,Thomas模型能较好地反映吸附过程特征,花生壳饱和吸附容量为9.4 mg/g。从动态吸附穿透曲线中可见,219 min时达到吸附穿透点,1312 min时达到吸附衰竭点。     

Fenton氧化法深度处理制革废水生化出水试验研究

采用Fenton氧化法深度处理以制革废水为主的园区生化处理出水,试验表明:影响Fenton氧化的因素从大到小依次为H2O2投加量、Fe2+浓度、pH、反应时间。当进水CODCr平均为116.6mg/L时,在H2O2投加量50mmol/L、Fe2+投加量10mmol/L、pH为3、反应时间60min的最佳条件下,出水CODCr平均为31.7mg/L;在H2O2投加量25mmol/L、Fe2+投加量7.5mmol/L、pH为5、反应时间40min的经济运行条件下,出水CODCr平均为46.6mg/L。经济条件下的运行成本比最佳条件下的运行成本可节约2.3元/m3。     

木质纤维素对水溶液中亚甲基蓝的吸附性能

以木质纤维素为吸附剂,分析吸附时间、初始浓度、pH值、温度等因素对木质纤维素吸附亚甲基蓝阳离子染料的影响.结果表明:木质纤维素对亚甲基蓝吸附300min后达到平衡,初始浓度超过180mg/L后吸附量不再增加,pH值由2增加到8时,吸附量由23.0mg/g增加到40.1 mg/g,温度对吸附量呈现先增大后减小的趋势.讨论...     

Photocatalytic degradation of di(2-ethylhexyl)phthalate adsorbed by chitin A.

Di(2-ethylhexyl)phthalate (DEHP) is a ubiquitous environmental contaminant due to its extensive use as a plasticiser and its persistence. Currently, there is no cost-effective treatment method for its removal from industrial wastewater. In a previous study, DEHP was effectively adsorbed from aqueous solution by biosorption onto chitinous materials. Biosorption can pre-concentrate DEHP from the aqueous phase for further treatment. As biosorption cannot degrade DEHP, in this study the degradation (and detoxification) of DEHP adsorbed onto chitinous material by photocatalytic oxidation (PCO) is attempted. PCO relies on hydroxyl radical (.OH), which is a strong oxidising agent, for the oxidative degradation of pollutants. It is a non-selective process which can degrade DEHP adsorbed onto chitinous material. The first part of this study is the optimisation of the degradation of adsorbed DEHP by PCO. Adsorption was carried out in the physicochemical conditions optimised in the previous study, with 500 mg/L chitin A and 40 mg/L DEHP at initial pH 2, 22+/-2 degrees C and 150 rpm agitation for 5 min. After optimisation of PCO, a 61% removal efficiency of 10 mg/L of DEHP was achieved within 45 min under 0.65 mW/cm2 of UV-A with 100 mg/L TiO2, and 10 mM of H2O2 at initial pH 12. The optimisation study showed that UV-A and TiO(2) are essential for the degradation of DEHP by PCO. The degradation intermediates/products were identified by GC-MS analysis. GC-MS results showed that the di(2-ethylhexyl) side chain was first degraded, producing phthalates with shorter side chains. Further reaction produced phathalic anhydride and aliphatic compounds such as alkanol and ester. The toxicities of parental and degradation intermediates in the solution phase and on chitinous materials were followed by the Microtox test. Results indicated that toxicity can be removed after 4 h treatment by PCO. Thus the decontamination of DEHP by integrating biosorption and PCO is feasible.     

Poly(acrylic acid) modifying bentonite with in-situ polymerization for removing lead ions

In this paper, a new kind of poly(acrylic acid) modified clay adsorbent, the poly(acrylic acid)/bentonite composite (PAA/HB) was prepared by in-situ polymerization, and utilized to remove lead(II) ions from solutions. The maximum adsorption of adsorbent is at pH 5 for metal ions, whereas the adsorption starts at pH 2. The effects of contact time (5-60 min), initial concentration of metal ions (200-1,000 mg/L) and adsorbent dosage (0.04-0.12 g/100 mL) have been reported in this article. The experimental data were investigated by means of kinetic and equilibrium adsorption isotherms. The kinetic data were analyzed by the pseudo-first-order and pseudo-second-order equation. The experimental data fitted the pseudo-second-order kinetic model very well. Langmuir and Freundlich isotherms were tried for the system to better understand the adsorption isotherm process. The maximal adsorption capacity of the lead(II) ions on the PAA/HB, as calculated from the Langmuir model, was 769.2 mg/g. The results in this study indicated that PAA/HB was an attractive candidate for removing lead(II) (99%).     

Colloidal silica removal in coagulation processes for wastewater reuse in a high-tech industrial park.

Four experiments of coagulation and flocculation were conducted to investigate the characteristics of colloidal silica removal in a high-tech industrial wastewater treatment plant for reclamation and reuse of the effluent. Experimental results illustrated that poly-aluminium chloride (PACl) showed higher performances on colloidal silica removal than alum. Interestingly, the two coagulants demonstrated the same capacity on silica removal. The specific silica removal capacity was approximately 0.135 mg SiO2/mg Al2O3 when the dosage of coagulants was in the range 30-150 mg/L Al2O3. In addition, the silica was reduced significantly at the condition of pH above 8. Experimental data implied that precipitation of aluminium flocs was the major mechanism for colloid silica removal in PACl and alum coagulation, besides, charge adsorption was also important for improving removal efficiency. Moreover, the addition of polyacrylic acid (PAA) as a flocculant could slightly advance silica removal in the PACl coagulation. The combined PACl/PAA/flocs coagulation was effective for the removal of colloidal silica, soluble COD, and turbidity and also suitable as a pretreatment unit in wastewater reclamation and reuse processes.