Adsorption characteristics of methylene blue on poplar leaf in batch mode: Equilibrium,kinetics and thermodynamics

Adsorption characteristics of methylene blue (MB) from aqueous solution on natural poplar leaf were investigated. Batch experiments were carried out to study the effects of initial pH, contact time, adsorbent dosage, and initial MB concentration, salt concentration (Ca²⁺ and Na⁺) as well as temperature on MB adsorption. The optimum condition for adsorption was found at pH 6–9 and adsorbent dosage of 2 g L⁻¹. The equilibration time was 240 min. The salt concentration had a negative effect on MB removal. The equilibrium data were analyzed with Langmuir, Freundlich and Koble-Corrigan isotherm models using nonlinear regression method. The adsorption process was more effectively described by Langmuir isotherm based on the values of the correlation coefficient R² and chi-square statistic x². The maximum monolayer adsorption capacity of poplar leaf from the Langmuir model was 135.35 mg g⁻¹ at 293 K. The pseudo second order equation provided a better fit to experimental data in the kinetic studies. Intraparticle diffusion was involved in adsorption process, but it was not the only rate-controlling step. Thermodynamic quantities such as ΔG, ΔH and ΔS were calculated, indicating that the adsorption process was spontaneous and endothermic. Dye-adsorbent interactions were examined by FTIR and SEM analysis. The FTIR results suggested that there were hydroxyl and carboxyl groups on the surface of poplar leaf, which would make MB adsorption possible. The SEM images showed effective adsorption of MB molecules on the adsorbent surface.     

Removal of Pb(II) from Aqueous Solutions by using Chitosan Coated Zero Valent Iron Nanoparticles

This study reports the synthesis, characterization, and application of chitosan coated zero valent iron nanoparticles (CTS-Fe⁰) in the removal of Pb(II) from aqueous medium. This nano adsorbent showed a high adsorption capacity and efficient adsorption towards Pb(II) in aqueous medium. Adsorption of Pb(II) on CTS-Fe⁰ obeyed pseudo-second order kinetics and was controlled by a film diffusion process. Among the various isotherm models the experimental data followed the Langmuir isotherm and the maximum adsorption capacity was found to be 666.6 mg/g at pH 5.0 and 318 K. The sorption mean free energy from D-R isotherm was found to be 72, 131, and 177 J/mol at 298, 308, and 318 K, respectively, indicating a physical sorption. The percentage of Pb(II) removal by CTS-Fe⁰ particles is more than 90% at 318 K. The calculated thermodynamic parameters showed that the adsorption of Pb(II) is feasible, spontaneous, and endothermic in nature. Experimental results indicated that the CTS-Fe⁰ appears to be a promising adsorbent for the removal of Pb(II) from aqueous media.     

Removal of heavy metals from aqueous solution by poly(acrylamide-co-acrylic acid) modified with porous materials

In this study, a series of poly acrylamide-co-acrylic acid/NaY zeolite, poly acrylamide-co-acrylic acid/MCM-41, and poly acrylamide-co-acrylic acid/clinoptilolite nanocomposites were synthesized. These materials were characterized by using FT-IR spectroscopy, XRD, TGA, and SEM. Removal capacity of Pb(II) and Cd(II) ions in aqueous solutions by using these nanocomposites was investigated with controlled time, initial metal ions concentration, pH values, adsorbent content, and temperature by using atomic absorption spectrometry. Results show that these nanocomposites have further adsorption related to NaY, MCM-41, and clinoptilolite. Poly(AAm-co-AAc)/NaY, poly(AAm-co-AAc)/MCM-41, and poly(AAm-co-AAc)/clinoptilolite exhibit superior Pb(II) (about 90–99%) and Cd(II) (about 88–98%) adsorption behavior at room temperature and the poly(AAm-co-AAc)/NaY nanocomposite had the best adsorption behavior. Finally, the equilibrium removal performance of the composites is analyzed according to the Langmuir and Freundlich adsorption isotherm model that shows result fitted to Langmuir model and have monolayer adsorption.     

Removal of Ni(II), Cd(II), and Pb(II) from a ternary aqueous solution by amino functionalized mesoporous and nano mesoporous silica

In the present study, the application for the removal of Ni(II), Cd(II) and Pb(II) ions from aqueous solution by using mesoporous silica materials, namely, MCM-41, nanoparticle of MCM-41, NH₂-MCM-41 (amino functionalized MCM-41) and nano NH₂-MCM-41 was investigated. Suitable adsorbents preparation techniques were developed in the laboratory. The effects of the solution pH, metal ion concentrations, adsorbent dosages, and contact time were studied. It was found that NH₂-MCM-41 showed the highest uptake for metal ions in aqueous solution. The results indicated that the adsorption of Ni(II), Cd(II) and Pb(II) ions on the surface of the adsorbent was increased with increasing solution pH. The experimental data were analyzed using the Langmuir and Freundlich equations. Correlation coefficients were determined by analyzing each isotherm. It was found that the Langmuir equation showed better correlation with the experimental data than the Freundlich. According to the parameters of the Langmuir isotherm, the maximum adsorption capacity of NH₂-MCM-41 for Ni(II), Cd(II) and Pb(II) was found to be 12.36, 18.25 and 57.74 mg/g, respectively. The kinetic data of adsorption reactions and the evaluation of adsorption equilibrium parameters were described by pseudo-first-order and pseudo-second-order equations. The synthesized solid sorbents were characterized by Fourier transform infrared (FT-IR) spectrometry, X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen sorption measurements.     

Lead(II) Adsorption from Aqueous Solution by Poly(ethylene terephthalate)-g-Acrylamide Fibers

In this study, a reactive fibrous adsorbent was prepared by graft copolymerization of Acrylamide (AAm) onto poly(ethylene terephthalate) (PET) fibers and the adsorption properties of Pb(II) ion from aqueous solution by the reactive fibers were examined by batch equilibration technique. The effects of graft yield, pH, adsorption time, initial ion concentration and adsorption temperature on the adsorption amount of Pb(II) ion was studied. The results show that the adsorption amounts of Pb(II) ion increased with grafting yield, shaking time, initial ion concentration and adsorption temperature. Adsorption of Pb(II) ion was strongly affected by pH. A Lagergren pseudo-second-order was the model that best described the adsorption mechanism. It was found that the adsorption isotherm of the Pb(II) ion fit Langmuir-type isotherms. From the Langmuir equation the adsorption capacity was found as 39.57 mg/g fiber for Pb(II) ion for the copolymer with a graft yield of 15.7%. Quantitative desorption of Pb(II) from reactive fibers were found to be 96% by 5 M HNO₃. Five adsorption–desorption cycles demonstrated that the reactive fibers were suitable for repeated use without considerable change in adsorption capacity. The results of the thermodynamic study indicated that the adsorption processes was endothermic and spontaneous.     

Kinetic and equilibrium studies of Pb(II) and Cd(II) removal from aqueous solution onto colemanite ore waste

The adsorption characteristics of Pb(II) and Cd(II) onto colemanite ore waste (CW) from aqueous solution were investigated as a function of pH, adsorbent dosage, contact time, and temperature. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the adsorption isotherms. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The adsorption capacity of CW was found to be 33.6 mg/g and 29.7 mg/g for Pb(II) and Cd(II) ions, respectively. Analyte ions were desorbed from CW using both 1 M HCl and 1 M HNO₃. The recovery for both metal ions was found to be higher than 95%. The mean adsorption energies evaluated using the D-R model indicated that the adsorption of Pb(II) and Cd(II) onto CW were taken place by chemisorption. The thermodynamic parameters (ΔG^o, ΔH^o and ΔS^o) showed that the adsorption of both metal ions was feasible, spontaneous and exothermic at 20-50 °C. Adsorption mechanisms were also investigated using the pseudo-first-order and pseudo-second-order kinetic models. The kinetic results showed that the adsorption of Pb(II) and Cd(II) onto CW followed well pseudo-second order kinetics.     

The use of exhausted olive cake ash (EOCA) as a low cost adsorbent for the removal of toxic metal ions from aqueous solutions

The removal characteristics of cadmium (Cd(II)) and nickel (Ni(II)) ions from aqueous solution by exhausted olive cake ash (EOCA) were investigated under various conditions of contact time, pH, initial metal concentration and temperature. Batch kinetic studies showed that an equilibrium time of 2 h was required for the adsorption of Ni(II) and Cd(II) onto EOCA. Equilibrium adsorption is affected by the initial pH (pH₀) of the solution. The pH₀ 6.0 is found to be the optimum for the individual removal of Cd(II) and Ni(II) ions by EOCA. The adsorption test of applying EOCA into synthetic wastewater revealed that the adsorption data of this material for nickel and cadmium ions were better fitted to the Langmuir isotherm since the correlation coefficients for the Langmuir isotherm were higher than that for the Freundlich isotherm. The estimated maximum capacities of nickel and cadmium ions adsorbed by EOCA were 8.38 and 7.32 mg g⁻¹, respectively. The thermodynamic parameters for the adsorption process data were evaluated using Langmuir isotherm. The free energy change (ΔG°) and the enthalpy change (ΔH°) showed that the process was feasible and endothermic respectively. As the exhausted olive cake is discarded as waste from olive processing, the adsorbent derived from this material is expected to be an economical product for metal ion remediation from water and wastewater.     

Removal of Pb(II) from Aqueous Solution by Cross-linked Starch Phosphate Carbamate

The adsorption process of Pb(II) ions from aqueous solution by water-insoluble starch phosphate carbamates was investigated. The influences of adsorption conditions, such as adsorption time, adsorbent dose, pH, content of the substituent groups, initial Pb(II) concentration, and temperature, were thoroughly studied. It was shown that an adsorption time of 20 min is sufficient to reach the adsorption equilibrium, the adsorption equilibrium data follow well the Langmuir isotherm model, and the adsorption of Pb(II) ions on cross-linked starch phosphate carbamate is endothermic in nature. For the cross-linked starch phosphate carbamate (CSPC3) with a phosphate group content of 3.10 mmol/g and a carbamate group content of 1.40 mmol/g, the maximum adsorption capacity evaluated from the Langmuir isotherm towards Pb(II) is 2.01 mmol/g. In addition, repeated adsorption/desorption cycles were performed to examine the reusability of adsorbents and the recovery efficiency of Pb(II) ions. The adsorption capacity of Pb(II) ions by CSPC3 decreased from 1.85 to 1.47 mmol/g for three cycles.     

Removal Characteristics of Cd(II), Cu(II), Pb(II), and Zn(II) by Natural Mongolian Zeolite through Batch and Column Experiments

The removal characteristics of Cd(II), Cu(II), Pb(II), and Zn(II) from model aqueous solutions by 5 natural Mongolian zeolites were investigated. The adsorption of metals on zeolites reached a plateau value within 6 h. The adsorption kinetic data were fitted with adsorption kinetic models. The equilibrium adsorption capacity of the zeolites was measured and fitted using Langmuir and Freundlich isotherm models. The order of adsorption capacity of zeolite was Pb(II) > Zn(II) > Cu(II) > Cd(II). The maximum adsorption capacity of natural zeolite depends on its cation exchange capacity and pH. The leaching properties of metals were simulated using four leaching solutions. The results show that natural zeolite can be used as an adsorbent for metal ions from aqueous solutions or as a stabilizer for metal-contaminated soils.     

Removal of arsenic from aqueous solution using polyaniline/rice husk nanocomposite

The present study deals with the adsorption of arsenic ions from aqueous solution on polyaniline/rice husk (PAn/RH) nanocomposite. Batch studies were performed to evaluate the influence of various experimental parameters like pH, adsorbent dosage, contact time and the effect of temperature. Optimum conditions for arsenic removal were found to be pH 10, adsorbent dosage of 10 g/L and equilibrium time 30 minutes. Adsorption of arsenic followed pseudo-second-order kinetics. The equilibrium adsorption isotherm was better described by Freundlich adsorption isotherm model. The adsorption capacity (q _max ) of PAn/RH for arsenic ions in terms of monolayer adsorption was 34.48 mg/g. The change of entropy (ΔS⁰) and enthalpy (ΔH⁰) was estimated at −0.066 kJ/(mol K) and −22.49 kJ/mol, respectively. The negative value of the Gibbs free energy (ΔG⁰) indicates feasible and spontaneous adsorption of arsenic on PAn/RH.     

Adsorption Characteristics of Congo Red from Aqueous Solution onto Tea Waste

The feasibility of using tea waste (TW) as a low-cost adsorbent for the adsorption of an anionic dye (Congo red) from aqueous solution has been investigated. Adsorption in a batch process was conducted to study the effect of adsorbent dosage, initial dye concentration, contact time, pH, and temperature. The experimental data were analyzed by the Langmuir, Freundlich, and Temkin models. The adsorption system was best described by the Langmuir isotherm (R ² > 0.99). Adsorption kinetics followed a pseudo-second-order model (R ² > 0.99). The effect of mechanical treatment (vibratory mill) was also studied. The experimental results showed that using this physical treatment leads to an increase in the adsorption capacity of TW from 32.26 to 43.48 mg/g. Thermodynamic analyses revealed that the adsorption of Congo red on TW was endothermic and spontaneous in nature. The results indicated that TW can be employed as a potential low-cost adsorbent for the removal of Congo red from aqueous solution.     

Adsorption of Nickel from aqueous solution by the use of low-cost adsorbents

The removal of Ni(II) from aqueous solution by different adsorbents was investigated. Calcined phosphate, red mud, and clarified sludge (a steel industry waste material) were used for the adsorption studies. The influence of pH, contact time, initial metal concentration, adsorbent nature and concentration on the selectivity and sensitivity of the removal process was investigated. The adsorption process was found to follow a first-order rate mechanism and rate constant was evaluated at 30 °C. Langmuir and Freundlich adsorption isotherms fit well in the experimental data and their constants were evaluated. The thermodynamic equilibrium constant and the Gibbs free energy were calculated for each system. The adsorption capacity (q _max ) calculated from Langmuir isotherm and the values of Gibbs free energy obtained showed that calcined phosphate has a higher capacity and affinity for the removal of Ni(II) compared to the other adsorbents used in the study.     

Removal of Pb(II) from aqueous solutions by adsorption onto clayey soil of Indian origin: Equilibrium, kinetic and thermodynamic profile

The feasibility of applying natural, untreated clayey soil as low-cost alternative adsorbent for Pb(II) removal from aqueous solutions was investigated with a batch experimental set-up. Experiments were carried out as a function of initial solution pH (1?C8), contact time (10?C360 min), initial Pb(II) concentration (20?C100 mg L^?1), adsorbent dose (0.5?C5 g) and temperature (303?C333 K). Adsorption equilibrium data were well described by the Langmuir isotherm with maximum adsorption capacity of 121.86 mg g^?1 at 303 K. Adsorption of Pb(II) followed pseudo-second-order kinetics. Gibbs free energy (??G⁰) was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. The adsorbent was easily regenerated by using 0.1M HNO₃ solution and was reused for five sorptiondesorption cycles without any considerable loss in adsorption capacity. It could be concluded that clayey soil may be used as an inexpensive and effective adsorbent without any treatment or any other modification for the removal of Pb(II) ions from aqueous solutions.     

A novel lead ion‐imprinted chelating nanofiber: Preparation,characterization, and performance evaluation

A novel Pb(II) ion‐imprinted chelating nanofibers (nIIP), synthesized by combining electrospinning with surface ion imprinting technique, was reported in this study. nIIP was characterized with Fourier transmission infrared spectrometry and scanning electron microscopy, respectively. The performance of nIIP for Pb(II) sorption was conducted through a batch adsorption experiments. Experimental data showed that adsorption capacity of nIIP was much higher than that of non‐ion imprinted chelating acrylic microfibers (mNIP) derived from commercial available acrylic microfibers, and adsorption behaviors agreed well with pseudo‐second‐order kinetic and Langmuir isotherm model. The values of Gibbs free energy change derived from experimental data suggested that the adsorption Pb(II) on nIIP is spontaneous and favorable at high temperature. In addition, nIIP had the highest selectivity among three tested fibrous adsorbents for Pb(II) from binary metal solution, the selectivity coefficients for Pb(II) from binary metal solution of Pb(II)/Cu(II), Pb(II)/Ni(II), and Pb(II)/Cd(II) onto nIIP were 47, 101, and 162, respectively. Besides, a forty adsorption/desorption cycles revealed that nIIP was a promising recyclable adsorbent. In conclusion, the novel nIIP is a highly effective adsorbent for enrichment and separation of Pb(II) in the presence of competitive ions in aqueous solution, and it is potential to be applied for recovering metals from heavy metal polluted industrial wastewater such as Pb(II)/Cd(II), Pb(II)/Ni(II), and Pb(II)/Cu(II) polluted wastewater. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41507.     

颗粒赤泥吸附剂对重金属离子的吸附性能研究

以氧化铝生产产生的工业固废——赤泥为原料,采用生石灰熟化后煅烧造粒方法,制备了颗粒状赤泥吸附材料。将制得的吸附材料用于水体中Cu2+、Pb2+、Cd2+的去除。研究了吸附时间、溶液pH值、吸附剂投加量对吸附效果的影响,在吸附作用时间、pH值、投加量相同的情况下,颗粒赤泥对3种金属离子的去除效果的大小顺序为Pb2+、Cd2+、Cu2+。颗粒赤泥吸附材料对3种金属离子的等温吸附规律可分别用Langmuir等温式、Langmuir等温式和Freundlich等温式较好地进行描述。颗粒赤泥吸附剂对3种重金属离子吸附饱和容量大,达平衡时间短,具较好的吸附性能。     

Adsorption of Pb(II) from aqueous solution to Ni-doped bamboo charcoal

Bamboo charcoal (BC) obtained by pyrolysis of Makino bamboo in the absence of oxygen was used as support for the preparation of Ni-doped adsorbent (Ni-BC). The low-cost composite was characterized and used as an adsorbent for Pb(II) removal from water. The results showed that both BET surface area and total pore volume of Ni-BC increased. The adsorption of Pb(II) strongly depended on solution pH, temperature and ionic strength. The adsorption isotherms followed Langmuir isotherm model well, and the maximum adsorption capacities of Pb(II) at 298 K were 25.0 and 142.7 mg/g for BC and Ni-BC, respectively. The adsorption processes were well fitted by pseudo-second-order kinetic model. Thermodynamic parameters showed that the adsorptions of Pb(II) onto both adsorbents were feasible, spontaneous, and exothermic under the studied conditions. The spent Ni-BC could be readily regenerated for reuse.     

Polymer‐grafted banana (Musa paradisiaca) stalk as an adsorbent for the removal of lead(II) and cadmium(II) ions from aqueous solutions: kinetic and equilibrium studies

This study examined the effectiveness of a new adsorbent prepared from banana (Musa paradisiaca) stalk, one of the abundantly available lignocellulosic agrowastes, in removing Pb(II) and Cd(II) ions from aqueous solutions. The adsorbent (PGBS‐COOH) having a carboxylate functional group at its chain end was synthesized by graft copolymerization of acrylamide on to banana stalk, followed by functionalization. Batch adsorption experiments were carried out as a function of solution pH, ionic strength, contact time, metal concentration, adsorbent dose and temperature. A pH range of 5.5–8.0 was found to be effective for the maximum removal for both Pb(II) and Cd(II). Metal uptake was found to decrease with increase in ionic strength due to the expansion of the diffuse double layer and, more importantly, the formation of some chloro complexes (since NaCl was used in the adjustment of ionic strength), which do not appear to be adsorbed to the same extent as cations [M²⁺ and M(OH)⁺]. The kinetic studies showed that an equilibrium time of 3 h was needed for the adsorption of Pb(II) and Cd(II) on PGBS‐COOH and adsorption processes followed a pseudo‐second‐order equation. The Langmuir isotherm model fitted the experimental equilibrium data well. The maximum sorption capacity for Pb(II) and Cd(II) ions was 185.34 and 65.88 mg g^?1, respectively, at 30 °C. The thermodynamic parameters such as changes in free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were derived to predict the nature of adsorption. The isosteric heat of adsorption was found to be independent of surface coverage. Adsorption experiments were also conducted using a commercial cation exchanger, Ceralite IRC‐50, for comparison. Synthetic wastewater samples were treated with the adsorbent to demonstrate its efficiency in removing Pb(II) and Cd(II) ions from industrial wastewaters. Acid regeneration was tried for several cycles with a view to recovering the sorbed metal ions and also restoring the sorbent to its original state. Copyright © 2005 Society of Chemical Industry     

Mercury (II) adsorption by activated carbon made from sago waste

The preparation of activated carbon (AC) from sago industry waste is a promising way to produce a useful adsorbent for Hg (II) removal, as well as dispose of sago industry waste. The AC was prepared using sago industry waste with H₂SO₄ and (NH₄)₂S₂O₈ and physico-chemical properties of AC were investigated. Adsorptive removal of mercury (II) from aqueous solution onto AC prepared from sago industry waste has been studied under varying conditions of agitation time, metal ion concentration, adsorbent dose, particle size and pH to assess the kinetic and equilibrium parameters. Adsorption equilibrium was obtained in 105 min for 20 mg l⁻¹ and 120 min for 30, 40, and 50 mg l⁻¹ Hg (II) concentrations. The Langmuir and Freundlich equilibrium isotherm models were found to provide an excellent fitting of the adsorption data, with r² 0.9999 and 0.9839, respectively. The adsorption capacity of Hg (II) (Q_o) obtained from the Langmuir equilibrium isotherm model was found to be 55.6 mg g⁻¹ at pH 5.0 for the particle size range of 125-250 μm. The percent removal increased with an increase in pH from 2 to 10. This adsorbent was found to be effective and economically attractive.     

A novel agricultural waste based adsorbent for the removal of Pb(II) from aqueous solution: Kinetics,equilibrium and thermodynamic studies

Fig sawdust was used as a precursor for the production of activated carbon by chemical activation with H₃PO₄. The developed Fig sawdust activated carbon (FSAC) was used as a biosorbent for the removal of Pb(II) from aqueous solution. Highest adsorption of Pb(II) (95.8%) was found at pH 4. Equilibrium data fitted very well with the Langmuir isotherm model. Maximum adsorption capacity was determined 80.645 mg g⁻¹ at pH 4. Kinetic studies demonstrated that the adsorption followed a pseudo second order kinetics model. The negative value of ΔG° confirmed the feasibility and spontaneity of FSAC for Pb(II) adsorption.