Application of 'waste' wood-shaving bottom ash for adsorption of azo reactive dye

The utilization of wood-shaving bottom ash (WBA) for the removal of Red Reactive 141 (RR141), an azo reactive dye, was investigated. WBA/H(2)O and WBA/H(2)SO(4) were made by treating WBA with water and 0.1M H(2)SO(4), respectively, to increase adsorption capacity. Adsorption of RR141 from reactive dye solution (RDS) and reactive dye wastewater (RDW) by WBA/H(2)O and WBA/H(2)SO(4) involved the BET surface area and pore size diameter. Properties of adsorbents, effect of contact time, initial pH of solution, dissolved metals and elution studies indicated that the decolorisation mechanism involved both chemical adsorption and precipitation with calcium ions. In addition, the WBA/H(2)SO(4) surface might contain sulphate-cation complexes that were specific to enhancing dye adsorption from RDW. The adsorption isotherm had a best fit by the Freundlich model. Freundlich parameters showed that WBA/H(2)O used more heterogeneous surface than WBA/H(2)SO(4) and activated carbon for RDW adsorption. A thermodynamic study indicated that RDW adsorption was an endothermic process. The maximum dye adsorption capacities of WBA/H(2)O, WBA/H(2)SO(4) and activated carbon obtained from a Langmuir model at 30 degrees C were 24.3, 29.9, and 41.5mgl(-1), respectively. In addition, WBA/H(2)O and WBA/H(2)SO(4) could reduce colour and high chemical oxygen demand (COD) of real textile wastewater. According to the difficulty in the elution study, it was an environmentally safe disposal of this waste. Therefore, WBA, a waste from combustion of wood shavings, was suitable to be used as an effective adsorbent for azo reactive dye removal.     

Adsorption of methylene blue from aqueous solution by jackfruit (Artocarpus heteropyllus) leaf powder: A fixed-bed column study

Continuous fixed-bed studies were undertaken to evaluate the efficiency of jackfruit leaf powder (JLP) as an adsorbent for the removal of methylene blue (MB) from aqueous solution under the effect of various process parameters like bed depth (5–10 cm), flow rate (30–50 mL/min) and initial MB concentrations (100–300 mg/L). The pH at point of zero charge (pH_PZC) of the adsorbent was determined by the titration method and a value of 3.9 was obtained. A FTIR of the adsorbent was done before and after the adsorption to find the potential adsorption sites for interaction with methylene blue molecules. The results showed that the total adsorbed quantities and equilibrium uptake decreased with increasing flow rate and increased with increasing initial MB concentration. The longest breakthrough time and maximum MB adsorption were obtained at pH 10. The results showed that the column performed well at low flow rate. Also, breakthrough time and exhaustion time increased with increasing bed depth. The bed-depth service time (BDST) model and the Thomas model were applied to the adsorption of MB at different bed depths, flow rates, influent concentrations and pH to predict the breakthrough curves and to determine the characteristic parameters of the column that are useful for process design. The two model predictions were in very good agreement with the experimental results at all the process parameters studied indicating that they were very suitable for JLP column design.     

A comparative study on the properties,mechanisms and process designs for the adsorption of non-ionic or anionic dyes onto cationic-polymer/bentonite

The adsorption properties and mechanisms of a cationic-polymer/bentonite complex (EPI-DMA/bentonite), prepared from polyepicholorohydrin-dimethylamine and bentonite, for non-ionic dyes (Disperse Blue SBL and Vat Scarlet R) and anionic dyes (Reactive Violet K-3R and Acid Dark Blue 2G) were investigated in this study. The solution pH, presence of salt and surfactant can significantly affect the dye removal efficiency. The equilibrium data were analyzed using the Langmuir and Freundlich models. The Langmuir model is the most suitable to describe non-ionic dye adsorption, but for anionic dyes the Freundlich model is best. The kinetic data for the adsorption of different dyes were analyzed using pseudo first- and second-order equations, and the experimental data conformed to the pseudo second-order kinetic model better. The possibility of intraparticle diffusion was also examined by using the intraparticle diffusion equation. The single-stage batch adsorber design for the adsorption of both types of dyes onto EPI-DMA/bentonite was studied based on the Langmuir isotherm model for non-ionic dyes and the Freundlich isotherm model for anionic dyes. The results showed that the required amount of EPI-DMA/bentonite for 95% dye removal in 5 L dye solution with a concentration of 50 mg/L is 378.0 g for DB SBL, 126.5 g for VS R, 9.7 g for RV K-3R and 15.5 g for ADB 2G.     

Biosorption of Reactive Black 5 from aqueous solutions by chitosan: Column studies

Fixed-bed column studies were carried out to investigate the dynamic sorption of Reactive Black 5 (RB5) onto chitosan. The effect of operating parameters such as initial dye concentration, superficial flow velocity, bed height and particle size on the sorption of RB5 onto chitosan was studied. Column regeneration, dye recovery and the possibility of reusing the regenerated chitosan were also investigated. The results show that both the breakthrough curves and the adsorption parameters of the column were strongly affected by the operating parameters studied. An analysis of the breakthrough curves indicated that adsorption was affected by mass transfer limitations, probably due to intraparticle diffusion. An empirical model was applied to describe the breakthrough curves, while the Bohart–Adams and BDST models were used to determine the operating parameters useful in the process design. Elution of the column with 0.01 mol L^?1 NaOH allowed the chitosan to be regenerated and the dye to be recovered and concentrated. The concentration factor was 10. Several cycles of adsorption–elution showed that the regenerated chitosan retained good adsorption efficiency and the elution efficiency was always higher than 80%.     

Removal of direct red 12B and methylene blue from water by adsorption onto Fe (III)/Cr (III) hydroxide, an industrial solid waste

Removal of direct red 12B and methylene blue by adsorption onto Fe (III)/Cr (III) hydroxide was studied using various parameters such as agitation time, dye concentration, adsorbent dose and pH. Equilibrium adsorption data followed both Langmuir and Freundlich isotherms. Adsorption followed second-order rate kinetics. The Langmuir adsorption capacity (Qo) was found to be 5.0 and 22.8 mg dye per g of the adsorbent for direct red 12B and methylene blue, respectively. Acidic pH was favorable for the adsorption of direct red 12B and basic pH for methylene blue. Desorption studies showed that chemisorption seems to be the major mode of adsorption.     

天然硅藻土作为吸附材料处理渗滤液的效果研究

利用天然硅藻土在静态条件下对垃圾渗滤液中的氨氮和COD的吸附效果进行了研究。结果表明：天然硅藻土对于氨氮的去除效率只有14．1％;但对COD的去除效率可以达到70．1％;天然硅藻土对于COD的饱和吸附量和吸附速度明显高于其对氨氮的饱和吸附量及吸附速度;在平衡浓度相当高的情况下,每克硅藻土具有吸附65．31mg COD的极限潜力。     

An Assessment of U(VI) removal from groundwater using biochar produced from hydrothermal carbonization

The ever-increasing growth of biorefineries is expected to produce huge amounts of lignocellulosic biochar as a byproduct. The hydrothermal carbonization (HTC) process to produce biochar from lignocellulosic biomass is getting more attention due to its inherent advantage of using wet biomass. In the present study, biochar was produced from switchgrass at 300 °C in subcritical water and characterized using X-ray diffraction, fourier transform infra-red spectroscopy, scanning electron micrcoscopy, and thermogravimetric analysis. The physiochemical properties indicated that biochar could serve as an excellent adsorbent to remove uranium from groundwater. A batch adsorption experiment at the natural pH (~3.9) of biochar indicated an H-type isotherm. The adsorption data was fitted using a Langmuir isotherm model and the sorption capacity was estimated to be ca. 2.12 mg of U g(-1) of biochar. The adsorption process was highly dependent on the pH of the system. An increase towards circumneutral pH resulted in the maximum adsorption of ca. 4 mg U g(-1) of biochar. The adsorption mechanism of U(VI) onto biochar was strongly related to its pH-dependent aqueous speciation. The results of the column study indicate that biochar could be used as an effective adsorbent for U(VI), as a reactive barrier medium. Overall, the biochar produced via HTC is environmentally benign, carbon neutral, and efficient in removing U(VI) from groundwater.     

Synthesis of biodegradable PVA/cellulose polymer composites and their application in dye removal

Environmentally sustainable composite films were synthesized using polyvinyl alcohol (PVA) and cellulose. Cellulose was extracted from the Agro-waste (sugarcane bagasse) using chemical pre-treatment followed by the acid-hydrolysis process. The composites were also used for the treatment of dye (Methylene blue; MB and Crystal violet dye; CV) and it was observed that the removal capacity of PVA/C was 70% for CV and 64.5% for MB dye. The biodegradation study of these composite films was also carried out using bacterial strains isolated from the marine waters of south Bengal. The biodegradation study of these polymer composites was characterized by FTIR, SEM, XRD, TGA, swelling properties, and weight loss. The results indicated that the PVA/C polymer showed a better rate of degradation (43%) than PVA (35%). Different loading parameters like pH, temperature, and inoculum dosage were studied to assess the degradation of the composite materials. Thus, biodegradable composite films were synthesized utilizing Agro-waste and had dye removal properties.     

Adsorption studies of hazardous malachite green onto treated ginger waste

Adsorption of malachite green (MG) from aqueous solution onto treated ginger waste (TGW) was investigated by batch and column methods. The effect of various factors such as initial dye concentration, contact time, pH and temperature were studied. The maximum adsorption of MG was observed at pH 9. Langmuir and Freundlich isotherms were employed to describe the MG adsorption equilibrium. The monolayer adsorption capacities were found to be 84.03, 163.9 and 188.6 mg/g at 30, 40 and 50 °C, respectively. The values of thermodynamic parameters like ΔG°, ΔH° and ΔS° indicated that adsorption was spontaneous and endothermic in nature. The pseudo second order kinetic model fitted well in correlation to the experimental results. Rechienberg's equation was employed to determine the mechanism of adsorption. The results indicated that film diffusion was a major mode of adsorption. The breakthrough capacities were also investigated.     

Electrocoagulation of blue reactive,red disperse and mixed dyes,and application in treating textile effluent

This study investigated the efficiency of electrocoagulation in removing color from synthetic and real textile wastewater. Two representative dye molecules were selected for the synthetic dye wastewater: a blue reactive dye (Reactive Blue 140) and a disperse dye (Disperse Red 1). The electrochemical technique showed satisfactory color removal efficiency and reliable performance in treating both individual and mixed dye types. The removal efficiency and energy consumption data showed that, for a given current density, iron was superior to aluminum in treating both the reactive dye and the disperse dye. With an initial dye concentration of 100 mg L^?1, the energy cost in achieving >95% color removal was on the order of 1 kWh m^?3 for both dyes. The effect of changing the initial pH of the samples on the removal efficiency and energy consumption was also studied. It was found that the design parameters used for the synthetic wastewater were less effective for treatment of real textile wastewater, with 1 in 5 tests on real wastewater failing.     

Thermochemical esterifying citric acid onto lignocellulose for enhancing methylene blue sorption capacity of rice straw

In this paper, rice straw was esterified thermochemically with citric acid (CA) to produce potentially biodegradable cationic sorbent. The modified rice straw (MRS) and crude rice straw (CRS) were evaluated for their methylene blue (MB) removal capacity from aqueous solution. The effects of various experimental parameters (e.g., initial pH, sorbent dose, dye concentration, ion strength, and contact time) were examined. The ratio of MB sorbed on CRS increased as the initial pH was increased from pH 2 to 10. For MRS, the MB removal ratio came up to the maximum value beyond pH 3. The 1.5g/l or up of MRS could almost completely remove the dye from 250mg/l of MB solution. The ratio of MB sorbed kept above 98% over a range from 50 to 450mg/l of MB concentration when 2.0g/l of MRS was used. Increase in ion strength of solution induced decline of MB sorption. The isothermal data fitted the Langmuir model. The sorption processes followed the pseudo-first-order rate kinetics. The intraparticle diffusion rate constant (k(id)) was greatly increased due to modification.     

Some properties of a granular activated carbon-sequencing batch reactor (GAC-SBR) system for treatment of textile wastewater containing direct dyes

Resting (living) bio-sludge from a domestic wastewater treatment plant was used as an adsorbent of both direct dyes and organic matter in a sequencing batch reactor (SBR) system. The dye adsorption capacity of the bio-sludge was not increased by acclimatization with direct dyes. The adsorption of Direct Red 23 and Direct Blue 201 onto the bio-sludge was almost the same. The resting bio-sludge showed higher adsorption capacity than the autoclaved bio-sludge. The resting bio-sludge that was acclimatized with synthetic textile wastewater (STWW) without direct dyes showed the highest Direct Blue 201, COD, and BOD(5) removal capacities of 16.1+/-0.4, 453+/-7, and 293+/-9 mg/g of bio-sludge, respectively. After reuse, the dye adsorption ability of deteriorated bio-sludge was recovered by washing with 0.1% sodium dodecyl sulfate (SDS) solution. The direct dyes in the STWW were also easily removed by a GAC-SBR system. The dye removal efficiencies were higher than 80%, even when the system was operated under a high organic loading of 0.36kgBOD(5)/m(3)-d. The GAC-SBR system, however, showed a low direct dye removal efficiency of only 57+/-2.1% with raw textile wastewater (TWW) even though the system was operated with an organic loading of only 0.083kgBOD(5)/m(3)-d. The dyes, COD, BOD(5), and total kjeldalh nitrogen removal efficiencies increased up to 76.0+/-2.8%, 86.2+/-0.5%, 84.2+/-0.7%, and 68.2+/-2.1%, respectively, when 0.89 g/L glucose (organic loading of 0.17kgBOD(5)/m(3)-d) was supplemented into the TWW.     

壳聚糖吸附处理废水的研究进展

壳聚糖吸附处理废水的研究包括其对废水吸附性能和吸附机理的研究两个方面。壳聚糖表现出了良好的吸附废水中重金属离子、染料分子和其它易引起变异物质的能力;壳聚糖对金属离子和染料的吸附机理模型研究理论意义重大,它将进一步推动壳聚糖的实际工程应用。     

Application of carbon adsorbents prepared from Brazilian-pine fruit shell for the removal of reactive orange 16 from aqueous solution: Kinetic,equilibrium, and thermodynamic studies

Activated (AC-PW) and non-activated (C-PW) carbonaceous materials were prepared from the Brazilian-pine fruit shell (Araucaria angustifolia) and tested as adsorbents for the removal of reactive orange 16 dye (RO-16) from aqueous effluents. The effects of shaking time, adsorbent dosage and pH on the adsorption capacity were studied. RO-16 uptake was favorable at pH values ranging from 2.0 to 3.0 and from 2.0 to 7.0 for C-PW and AC-PW, respectively. The contact time required to obtain the equilibrium using C-PW and AC-PW as adsorbents was 5 and 4 h at 298 K, respectively. The fractionary-order kinetic model provided the best fit to experimental data compared with other models. Equilibrium data were better fit to the Sips isotherm model using C-PW and AC-PW as adsorbents. The enthalpy and entropy of adsorption of RO-16 were obtained from adsorption experiments ranging from 298 to 323 K.     

Adsorption of malachite green and chrysoidine-Y by Sn-pillared clay

The aim of this research was to pillar the bentonite clay (Bt) with polyhydroxy tin chloride. The synthesized Tin-pillared interlayer clay (Sn-PILC) was characterized using X-ray diffraction (XRD), Fourier Transform Infrared spectra (FT-IR), Brunauer-Emmer Teller (BET) analysis, Thermogravimetric analysis (TGA), and Scanning Electron Microscopy (SEM). Adsorption capacity of raw-Bt and tin pillared interlayer clay (Sn-PILC) was examined for two dyes, namely, Malachite Green (MG) and Chrysoidine-Y (CY) from their aqueous solutions. The effects of physicochemical parameters like solution pH, dose, and dye concentration were investigated. The maximum adsorption efficiency at equilibrium dye concentration for Sn-PILC was 66.229 mg g^–1 for MG and 63.792 mg g^–1 for CY. Sn-PILC obeyed Langmuir isotherm for both the dyes whereas raw-Bt followed Freundlich isotherm. On the other hand, both adsorbents followed PFO as well as PSO kinetic model, indicating physisorption assisted by chemisorption. Thermodynamic studies were performed to determine the adsorption behavior of Sn-PILC for both the dyes. Regeneration studies revealed 80% efficiency up-to five adsorption-desorption cycles.     

Development of activated carbon from Nerium oleander flower and their rapid adsorption of direct and reactive dyes

The present study investigates the thermally activated carbon derived from Nerium oleander flower which was used an adsorbent. Physicochemical properties of Nerium oleander flower carbon (NOFC) were characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared for the removal of DTB (Direct Turquoise Blue) and RR-HE7B (Reactive red–HE7B) dyes from aqueous solution. Adsorption studies were carried out with different pH, adsorbent dose, contact time, and initial concentration dye solution. Optimum conditions for maximum removal of DTB and RR-HE7B was achieved to be pH 2 for both dyes, adsorbent dose of 100 mg and equilibrium time of 35 and 60 min, respectively, for NOFC. The maximum adsorption capacity of NOFC was found to be 33.33 and 19.60 mg g^?1, respectively, for the removal of dye solution. The mechanism of adsorption was studied by using different kinetic models and isotherms. The results clearly showed that the NOFC adsorption was fitted to pseudo–first-order for DTB and pseudo–second-order for RR-HE7B. Equilibrium data were well fitted with both isotherm models. According to the results, NOFC can effectively remove DTB and RR-HE7B from aqueous solutions.     

Rice husk ash as an effective adsorbent: evaluation of adsorptive characteristics for Indigo Carmine dye

Present study explored the adsorptive characteristics of Indigo Carmine (IC) dye from aqueous solution onto rice husk ash (RHA). Batch experiments were carried out to determine the influence of parameters like initial pH (pH(0)), contact time (t), adsorbent dose (m) and initial concentration (C(0)) on the removal of IC. The optimum conditions were found to be: pH(0)=5.4, t=8h and m=10.0 g/l. The pseudo-second-order kinetic model represented the adsorption kinetics of IC on to RHA. Equilibrium isotherms were analyzed by Freundlich, Langmuir, Temkin and Redlich-Peterson models using a non-linear regression technique. Adsorption of IC on RHA was favorably influenced by an increase in the temperature of the operation. The positive values of the change in entropy (DeltaS(0)) and heat of adsorption (DeltaH(0)); and the negative value of change in Gibbs free energy (DeltaG(0)) indicate feasible and spontaneous adsorption of IC on to RHA.     

Removal of basic dye (Astrazon Blue FGRL) using macroalga Caulerpa lentillifera

The macroalga Caulerpa lentillifera was found to have adsorption capacity for a basic dye, Astrazon Blue FGRL. For the whole range of concentrations employed in this work (20-1280 mgl(-1)), the adsorption reached equilibrium within the first hour. The kinetic data corresponded well with the pseudo second-order kinetic model where the rate constants decreased as initial dye concentrations increased. At low dye concentrations (20-80 mgl(-1)), an increase in the adsorbent dosage resulted in a higher removal percentage of the dye, but a lower amount of dye adsorbed per unit mass (q). The adsorption isotherm followed both the Langmuir and Freundlich models within the temperature range employed in this work (18-70 degrees C). The highest maximum adsorption capacity (q(m)) was obtained at 50 degrees C. The enthalpy of adsorption was estimated at 14.87 kJmol(-1) suggesting a chemical adsorption mechanism.     

Removal of the hazardous dye rhodamine B through photocatalytic and adsorption treatments

This paper reports on photocatalytic and adsorptive treatment of a hazardous xanthene dye, Rohdamine B, in wastewater. The photocatalytic degradation was carried out in the presence of the catalyst TiO(2) and the effects of pH, concentration of the dye, amount of TiO(2), temperature and electron acceptor H(2)O(2) on the degradation process were observed. It was found that photocatalytic degradation by TiO(2) is an effective, economical and faster mode of removing Rohdamine B from aqueous solutions. Attempts were also made to utilize activated carbon and rice husk as potential adsorbents to remove Rhodamine B from wastewater. The adsorption studies were carried out at 40, 50 and 60 degrees C, and the effects of pH, temperature, amount of adsorbents, concentration of adsorbate, etc., on the adsorption were measured. On the basis of adsorption data the Langmuir and Freundlich adsorption isotherm models were also confirmed. The adsorption isotherm constants thus obtained were employed to calculate thermodynamic parameters like Gibb's free energy, change in enthalpy and entropy. In order to observe the quality of wastewater COD measurements were also carried out before and after the treatments. A significant decrease in the COD values was observed, which clearly indicates that both photocatalytic and adsorption methods offer good potential to remove Rhodamine B from industrial effluents.     

Adsorption of eosin dye on activated carbon and its surfactant based desorption

The performance of activated carbon has been investigated for the adsorption of eosin dye dissolved in water. Eosin is anionic in nature and highly toxic. The effects of initial dye concentration, contact time, pH and temperature on adsorption of eosin by a fixed amount of activated carbon (1.0 g/L) have been studied in batch and column mode. The equilibrium data are successfully fitted to the Freundlich adsorption isotherm. The adsorption rate data are successfully explained by a pseudo second-order kinetic model. Breakthrough curves for column adsorption have also been studied. The regeneration of spent carbon by desorbing the dye has been experimentally investigated applying a surfactant enhanced carbon regeneration (SECR) technique using both cationic and anionic surfactants. An empirical kinetic model for dye desorption from the commercial activated carbon (CAC) using different surfactant and desorption techniques, viz. change in pH, has been proposed. The comparison between the model and the experimental results is found to be satisfactory.