Removal of basic dyes from aqueous solutions using natural clay

Adsorption properties of natural clay (from Eski?ehir of Turkey) were investigated by depending on different adsorption conditions such as different initial dye concentrations and contact times. The chemical composition of the natural clay was analyzed by X-ray fluorescence spectrometry (XRF). The removal of basic dyes such as Nile Blue (NB) and Brilliant Cresyl Blue (BCB) from aqueous solutions using natural clay in this study was described. After the equilibrium adsorption time of 8 h, the adsorption capacities for NB and BCB reach about 25 mg/g and 42 mg/g, respectively. Lagergren kinetic equation was used to test the experimental data to examine the controlling mechanism of adsorption processes. Adsorption data of the BCB and NB onto natural clay were fitted well by the pseudo-first-order model. The adsorption isotherms data were correlated with the Freundlich equation and the Freundlich constants K_f (mg/g) and n (intensity of adsorption) were calculated. The r² (regression coefficients) values were 0.9835 and 0.9849 for NB and BCB, respectively. The adsorption capacities of natural clay for NB and BCB have the following order: BCB > NB.     

Utilization of polyampholyte hydrogels for simultaneous removal of textile dyes from aqueous solutions

The study aimed to create hydrogel structures with greater functionality, otherwise known as polyampholytes (PAHs), and to use these in simultaneous removal studies for remazol-type dyes found in environmental waste waters. Adsorption studies were accomplished at 20°C and 35°C, indicated that adsorption process was exothermic in nature. The Q_m values for the PAH-dye systems were in the interval 111–122 mg dye/g PAH with Ads% from 94% to 98%. The ability of PAH hydrogels to adsorb two different species of dye molecules at the same time is an advantage of PAH adsorbents compared to other hydrogel adsorbents prepared in this area.     

Modeling of paper mill sewage sludge drying using artificial neural networks: Reduction of the training database through Taguchi’s method

Drying of sewage sludge is typically modeled as simultaneous heat and mass transfer phenomena. The capability of conventional models to take into account crust formation, cracks, and shrinking is limited. Artificial neural networks (ANNs) are suitable tools for dynamic representation of drying processes; however, obtaining a suitable database is a resource consuming task. Based on the Taguchi method, nine experiments were defined to set up a training database and to develop an ANN model. A high Pearson correlation coefficient was verified when comparing the drying kinetic curve generated by the ANN model with the one obtained during the validation experiments.     

The removal of cationic dyes from aqueous solutions by adsorption onto pistachio hull waste

The efficacy of pistachio hull powder (PHP) prepared from agricultural waste was investigated in this study as a novel adsorbent for the elimination of dye molecules from contaminated streams. Removal of methylene blue (MB) as a cationic model dye by PHP from aqueous solution was studied under different experimental conditions. The selected parameters were solution pH (2–10), PHP dosage (0.5–3 g/L), MB concentrations (100–400 mg/L), contact time (1–70), and solution temperature (20–50 °C). The experimental results indicated that the maximum MB removal could be attained at a solution pH of 8. The dosage of PHP was also found to be an important variable influencing the MB removal percentage. The removal efficiency of MB improved from 94.6 to 99.7% at 70 min contact time when the MB concentration was decreased from 300 to 100 mg/L at a pH and PHP dosage of 8 and 1.5 g/L, respectively. The kinetic analysis showed that the pseudo-second-order model had the best fit to the experimental data. The Langmuir equation provided the best fit for the experimental data of the equilibrium adsorption of MB onto PHP at different temperatures. In addition, the maximum adsorption capacity increased from 389 to 602 mg/g when the temperature was increased from 20 to 50 °C. The thermodynamic evaluation of MB adsorption on PHP revealed that the adsorption phenomenon under the selected conditions was a spontaneous physical process. Accordingly, pistachio hull waste was shown to be a very efficient and low-cost adsorbent, and a promising alternative for eliminating dyes from industrial wastewaters.     

Adsorption of cationic dye from aqueous solutions by activated carbon

Batch sorption experiments were carried out to remove a cationic dye, methylene blue (MB), from its aqueous solutions using a commercial activated carbon as an adsorbent. Operating variables studied were pH, stirring speed, initial methylene blue concentration and temperature. Adsorption process was attained to the equilibrium within 5 min. The adsorbed amount MB dye on activated carbon slightly changed with increasing pH, and temperature, indicating an endothermic process. The adsorption capacity of methylene blue did not significantly change with increasing stirring speed. The experimental data were analyzed by various isotherm models, and found that the isotherm data were reasonably well correlated by Langmuir isotherm. Adsorption measurements showed that the process was very fast and physical in nature. Thermodynamic parameters such as the adsorption entropy (ΔS^o) and adsorption enthalpy (ΔH^o) were also calculated as 0.165 kJ mol⁻¹ K⁻¹ and 49.195 kJ mol⁻¹, respectively. The ΔG^o values varied in range with the mean values showing a gradual increase from −0.256 to −0.780 to −2.764 and −7.914 kJ mol⁻¹ for 293, 313, 323 and 333 K, respectively, in accordance with the positive adsorption entropy value of the adsorption process.     

A nanoporous adsorbent for removal of furfural from aqueous solutions

The adsorption of furfural by a surfactant-containing nanoporous material is investigated in the present study. We used cetyltrimethylammonium bromide (CTAB) as the cationic surfactant for synthesis of MCM-48. Batch adsorption studies demonstrate that the surfactant-containing MCM-48 has a significant capacity for adsorption of furfural from aqueous solution. The parameters investigated in this study included pH, contact time, agitation speed and initial furfural concentration. The adsorption process of furfural is tested with Langmuir and Freundlich isotherm models. Application of the Langmuir isotherm to the systems yielded maximum adsorption capacity of 196.1 mg/g.     

Chitosan/polyaniline hybrid for the removal of cationic and anionic dyes from aqueous solutions

Nanostructured chitosan/polyaniline (CH/PANI) hybrid was synthesized via in situ polymerization of aniline in the presence of chitosan. The CH/PANI hybrid was characterized by FTIR spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The CH/PANI hybrid had a nanofibrous structure with an average diameter of 70 nm. This hybrid was employed as an ecofriendly and efficient adsorbent with high adsorption capacity for the removal of Acid Green 25 (AG) and methylene blue (MB) from aqueous solutions. AG and MB were used as anionic and cationic model dyes, respectively. The CH/PANI adsorbent showed high dependence on the pH of the medium with an excellent adsorption performance and regeneration manner. The kinetics and adsorption isotherms were studied. The CH/PANI hybrid follows the pseudo second-order adsorption kinetics and Temkin isotherm model for the adsorption of both AG and MB dyes. This assumes that the enthalpy of dyes molecules decreases with the adsorption on heterogeneous surface with various kinds of adsorption sites and as well as the ability to form multilayers of the dye. Also, intraparticle diffusion was found to play an important role in the adsorption mechanism. The maximum adsorption capacity was found to be 240.4 mg g⁻¹ of AG at pH 4 and 81.3 mg g⁻¹ of MB at pH 11. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47056.     

Nanocomposite hydrogels for selective removal of cationic dyes from aqueous solutions

Removal of organic dyes from waste water has received a significant attention in recent years. In this work, a set of nanocomposite hydrogels (NHs) were prepared and their capacity to absorb crystal violet (CV), a cationic dye, and acid yellow‐23 (AY), an anionic dye, from aqueous solutions was determined. NHs were prepared by in situ formation of Fe₃O₄ magnetic nanoparticles (MNPs) inside poly(acrylamide‐co‐4‐styrene sulfonic acid sodium salt) (P[AAm‐co‐SSA]) hydrogel matrices. The dye absorption capacity of the magnetic NHs (MNHs) was compared with simple hydrogels (hydrogels or SHs) without the MNPs The prepared hydrogels were characterized by FTIR, XRD, thermogravimetric analysis, high resolution TEM, field emission SEM, and vibrating sample magnetometer measurement. From HRTEM, it was confirmed that the prepared MNPs in hydrogel matrices were in the size range of about 8 to 10 nm. The MNHs showed greater swelling behavior as well as greater removal efficiency of cationic dye from aqueous solutions in comparison to the SHs. With increase of SSA mole percentage, dye removal efficiency was also increased for both types of hydrogels. The present study indicates that the hydrogels containing MNPs can be potentially used as an efficient absorbent material for removal of cationic dyes from waste water. POLYM. ENG. SCI., 56:776–785, 2016. © 2016 Society of Plastics Engineers     

Efficient removal of chemically toxic dyes using microorganism from activated sludge: Understanding sorption mechanism,kinetics, and associated thermodynamics

A systematic investigation was carried out for demonstrating the simple and cost-effective removal of toxic dyes using activated sludge from municipal wastewater. The sorption process was found to follow Freundlich isotherm and pseudo-second-order rate kinetics. Difference in sorption efficiency for activated and deactivated sludge in aerobic and anaerobic conditions revealed the involvement of different microorganism in sorption process with the indication of biodegradation. The sorption process was found to be spontaneous but entropy driven for Remazol Brilliant Blue R and Eriochrome Black T while enthalpy driven for Congo Red. The process was established to be a combination of adsorption as well as biodegradation.     

Removal and recovery of cationic dyes from aqueous solutions using spherical sulfonic lignin adsorbent

A novel spherical sulfonic lignin adsorbent, denoted as SSLA, was adopted to removal and recover the cationic dyes from aqueous solutions, e.g., Cationic Red GTL, Cationic Turquoise GB, and Cationic Yellow X‐5GL, and various affecting factors were optimized. It was found that the adsorption of cationic dyes on the adsorbent was initially concentration‐ and temperature‐dependent, and followed both the Freundlich and Langmuir isothermal adsorption. The positives values for ΔH indicated that the process was endothermic. The breakthrough adsorption capacities for GTL, GB, and X‐5GL were 536.0, 550.0, and 582.0 mg/g, respectively, which prevailed over the commercial powdered activated carbon and strongly acidic cation‐exchange resin R732 evidently. Additionally, the maximum recovery percentage could reach 93.2, 97.1, and 96.5% separately for GTL, GB, and X‐5GL, when a mixture of 3.0 mol/L HCl and alcohol with the volume ratio of 1 : 4 was adopted as eluant. Moreover, the results of the mobile desorption and recovery tests indicated that the maximum concentrations of GTL, GB, and X‐5GL in the eluants could reach 13,108, 13,980, and 13,520 mg/L, respectively. Only 6.3, 5.0, and 4.6% of adsorption capacities for GTL, GB, and X‐5GL decreases individually after 20 replicates of adsorption and desorption. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2284–2291, 2006     

Removal of cationic dyes from aqueous solutions by kaolin: Kinetic and equilibrium studies

Experimental investigations were carried out using commercially available kaolin to adsorb two different toxic cationic dyes namely crystal violet and brilliant green from aqueous medium. Kaolin was characterized by performing particle size distribution, BET surface area measurement and XRD analysis. The effects of initial dye concentration, contact time, adsorbent dose, stirring speed, pH, salt concentration and temperature were studied in batch mode. The extent of adsorption was strongly dependent on pH of solution. Free energy of adsorption (ΔG⁰), enthalpy (ΔH⁰) and entropy (ΔS⁰) changes were calculated. Adsorption kinetic was verified by pseudo-first-order, pseudo-second-order and intra-particle-diffusion models. The rate of adsorption of both crystal violet and brilliant green followed the pseudo-second-order model for the dye concentrations studied in the present case. The dye adsorption process was found to be external mass transfer controlled at earlier stage and intra-particle diffusion controlled at later stage. Calculated external mass transfer coefficient showed that crystal violet dye adsorbed faster than brilliant green on kaolin. Adsorption of crystal violet and brilliant green on kaolin followed the Langmuir adsorption isotherm.     

Investigation of Reactive Red Dye 198 removal using multiwall carbon nanotubes in aqueous solution

The present study evaluates the performance of multiwalled carbon nanotubes (MWCNTs) for removing Reactive Red Dye 198 (RR198) from the color wastewater. In this study, the influence of pH, adsorbent dose, initial dye concentration, and contact time on the RR198 adsorption by MWCNTs was investigated. The results showed increasing the dye concentration from 20 to 200 mg/L, removal efficiency decreased from 99.62% to 66.99%. Moreover, by increasing the pH from 3 to 10, the efficiency of dye removal decreased from 76.34% to 54.98%. Freundlich isotherm and pseudo-second-order kinetic model were the best models for describing the adsorption reactions.     

NaHCO处理胶乳生产污泥制备吸附剂对阳离子染料的吸附

以胶乳生产厂脱水污泥为原料、1.40mol/L的NaHCO₃作膨胀剂,60℃浸渍并超声处理30min,污泥烘干后再经高温炭化制备吸附剂,将其用于吸附阳离子兰X-GRRL染料溶液,考察炭化温度、炭化时间、吸附剂粒径、吸附剂投加量、吸附时间及溶液pH对吸附效果的影响,并对其吸附动力学和吸附等温线类型进行了探讨。结果表明：污泥在炭化温度700℃、炭化时间120min的条件下,制备的吸附剂（粒径<0.75mm）的比表面积为118.95m²/g,孔隙结构较为发达,对染料溶液吸附效果最佳;在振荡频率150r/min、吸附温度为25℃±0.10℃、初始染料质量浓度为250mg/L、吸附剂投加量为1.20g/L、溶液pH为5.47、吸附时间为300min时,溶液脱色率可达98.30%,染料吸附量为204.80mg/g;其吸附动力学可用准二级动力学方程进行描述;符合Langmuir型吸附等温线,属于单分子层吸附;吸附剂浸出液及吸附处理后的染料溶液的COD值分别为4.00mg/L和20.00mg/L,不会对水体造成二次污染。     

制浆造纸厂富铁污泥中Fe3+的电化学还原研究

采用电化学法将制浆造纸厂废水Fe^nton氧化产生的难处理富铁污泥中的Fe^3+还原为Fe^2+,以便于其再利用。研究表明,以不锈钢为阴极材料可较大幅度降低Fe^3+还原的过电位;当Fe^3+质量浓度为2000 mg/L时无需辅助电解质,在极水比为0.48 cm^2/mL,电流密度为0.65 mA/cm^2的条件下反应2 h,Fe^2+再生率可达60.1%,电流效率为92.1%。将酸处理后的富铁污泥溶液在上述条件下还原3 h,Fe^2+再生率达68.8%,电流效率近100%。电化学法是富铁污泥中Fe^3+再利用的可行方法。     

稻草作为生物吸附剂去除水溶液中偶氮染料的研究

用低值易得的稻草作为生物吸附剂对活性红和中性黄两种偶氮染料进行吸附处理研究,考察了吸附剂粒径、初始染料浓度、吸附时间、溶液初始pH等因素对染料吸附的影响。结果显示,吸附剂粒径200目、活性红染料浓度40mg/L、中性黄染料浓度50mg/L、吸附时间20min、吸附物剂量5g/L、初始pH2时,碎稻草对两种偶氮染料的吸附效果显著,分别达到活性红84%、中性黄94%。     

Reusable high performance of calcined Mg/Al hydrotalcite for the removal of Navy Blue and Yellow F3G dyes

Water pollution with dye chemicals from apparel industries is a serious problem in the world.Since most of dyes are potentially have toxic and carcinogenic effects on human,it is important to remove them before they are discharged to the environment.Among many methods available for dyes removal in water,adsorption is the easiest and economically feasible that has no major obstacle for practical appli-cations.In the present study,we tested calcined Mg/Al hydrotalcite (Mg/Al CHT) prepared by co-precipitation technique as an adsorbent for the removal of Navy Blue (NB) and Yellow F3G (YF3G) dyes.Mg/Al CHT was characterized by using a Fourier transform infrared (FTIR) spectrometer,an X-ray diffrac-tometer (XRD) and a scanning electron microscope (SEM).The results showed that Mg/Al CHT was highly effective as an adsorbent for the removal of NB and YF3G under mild-acidic condition (pH 4) with removal capacities (b) according to Langmuir isotherm model were 7.97 × 10-4 and 5.80 × 10-4 mol·g-1,respectively.Kinetics study showed that the adsorption of NB and YF3D on Mg/Al CHT followed pseudo-second order with rate constant (kp2) 11.57 × 103 and 11.75 × 103 g·mol-1·min-1,respectively.The spent adsorbent can be easily regenerated by simply calcining it at 450 ℃ for 3 h.Adsorption test on the mix-ture of NB and YF3G showed that the adsorption capacity of Mg/Al CHT was eightfold higher than that of Mg/Al HT and the value was maintained with repeated use.     

Removal of basic and acid dyes from aqueous solutions by a waste containing boron impurity

In this study, batch experiments were carried out for the sorption of basic blue 41 (BB 41), and acid blue 225 (AB 225) onto boron waste (BW) from boron enrichment plant. The operating variables studied are the initial dye concentration, contact time, solution pH, and adsorbent dosage. The experimental equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that the adsorption behavior of AB 225 and BB 41 could be described well reasonably by Langmuir and Temkin isotherms, respectively. Kinetics studies indicated that the adsorption of both dyes follow pseudo-second-order kinetics. The sorption of basic dye increased at high pH values, whereas the opposite was true for acidic dye. The results indicate that BW could be employed as low-cost alternatives to the commercially available adsorbents in wastewater treatment for the removal of acid and basic dyes.     

Adsorptive removal of cationic dye from aqueous solutions by ZnO/ZnMn2O4 nanocomposite

The ZnO/ZnMn₂O₄ nanocomposite (ZnMn) was used as adsorbent for the removal of cationic dye Basic Yellow 28 (BY28) from aqueous solutions. The adsorbent was characterized by X-ray diffraction, scanning electron microscope, TEM, Fourier transform infrared ray, BET, particle size distribution and zeta potential measurements. The adsorption parameters, such as temperature, pH and initial dye concentration, were studied. Kinetic adsorption data were analyzed using the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The Langmuir and Freundlich isotherm models were applied to fit the equilibrium data. The maximum adsorption capacity of BY28 was 48.8 mg g^?1. Various thermodynamic parameters, such as ΔG°, ΔH° and ΔS°, were calculated.     

Preparation of activated carbon from paper mill sludge by KOH-activation

The purpose of this study is the preparation of activated carbon using paper mill sludge collected from biological wastewater treatment plant. The char produced from pyrolysis of paper mill sludge was chemically activated with potassium hydroxide. A systematic investigation of the effect of activation agent ratio, activation temperature and time on the properties of the char was carried out in a rotary kiln reactor. The chemically activated carbons were characterized by measuring iodine and methylene blue number and specific surface area. The activated carbon prepared from char of paper mill sludge in this study had maximum iodine and methylene blue number of 726.0 mg/g and 152.0 mg/g, and specific surface area of 1,002.0 m²/g, respectively. The result of estimation on adsorption capacities of metals, the Freundlich isotherms, yields a fairly good fit to the adsorption data, indicating a monolayer adsorption of metals onto activated carbon prepared from char of paper mill sludge using a potassium hydroxide as the activating agents.     

Preparation of sodium carboxymethyl cellulose from paper sludge

BACKGROUND: This paper describes the reuse of paper sludge, an industrial solid waste, for the preparation of sodium carboxymethyl cellulose (CMC). The process includes pretreatment, basification and etherification. RESULTS: The optimal pretreatment condition involved the addition of 6.7% hydrochloric acid to the paper sludge for 30 min at 70 °C. The order of factors influencing the effect of reaction was: etherification temperature > sodium hydroxide dose > basification temperature > etherification time > sodium chloroacetate dose. The optimal preparation condition of CMC was: m_papersludge: m_{sodiumhydroxide}: m_{sodiumchloroacetate} = 0.9:0.8:1.15; basification at 40 °C; etherification at 60 °C for 1 h. Under these conditions, certified CMC with viscosity less than 20 mPa· s, DS more than 0.50 and purity more than 90% was produced. The results of Fourier transform infrared (FTIR) and X‐ray diffraction (XRD) spectra analyses indicated that the product has characteristics of high degree of substitution (DS) and low crystallinity. The coated paper using CMC prepared from paper sludge as a water retention agent can meet the quality standards of GB/T 10335.1‐2005. CONCLUSION: Preparation of CMC from paper sludge can be considered a feasible alternative, generating value‐added product and contributing to solving environmental problems resulting from paper sludge. Copyright © 2008 Society of Chemical Industry