Hybrid Amine-Functionalized Titania/Silica Nanoparticles for Solid-Phase Extraction of Lead,Copper, and Zinc from Food and Water Samples: Kinetics and Equilibrium Studies

In the present study, hybrid amine-functionalized titania/silica nanoparticles were employed as a new and novel adsorbent for solid-phase extraction of Pb²⁺, Cu²⁺, and Zn²⁺ ions prior to their determination using flame atomic absorption spectrometry. Under the best conditions (including adsorbent, 0.4 g; eluent, 5.0 mL nitric acid (HNO₃), 3.0 mol L^?1, 1.0 mL min^?1; and sample, pH 5.0, 3.0 mL min^?1), detection limits, adsorption capacities, and preconcentration factors were 0.12–0.24 μg L^?1, 7.1–20.7 mg g^?1, and 200, respectively. To predict the adsorption isotherms, different isotherm models were studied and the obtained results showed that the Langmuir model is the most suitable one to explain the experimental data. The kinetics of the reaction followed pseudo-second-order kinetic model. Thermodynamic parameters like free energy (ΔG ⁰) and enthalpy (ΔH ⁰) confirmed the spontaneous and exothermic nature of the process. The method was successfully applied for determination of the analytes in different food and water samples.     

Application of beech sawdust for removal of heavy metals from water: biosorption and desorption studies

In this work the efficiency of applying non-modified beech sawdust for the removal of Cu²⁺ and Cr³⁺ heavy metal ions from water solutions was examined. Parameters taken into consideration in the analysis of environment conditions were influence of sorbent concentration, initial concentration of metal ions, temperature effect, presence of additional substances in solution (NaCl and MgCl₂ inorganic salts and anionic and cationic surface-active compounds). Results of kinetic experiments were described by two models: pseudo-first-order and pseudo-second-order; equilibrium results were approximated with five non-linear isotherm models. Maximum sorption capacity at a temperature of 20 °C and pH 5.0 was 30.22 mg g^?1 for Cu²⁺ ions and 41.86 mg g^?1 for Cr³⁺ ions. The positive value of the thermodynamic parameter ΔH° indicates the endothermic nature of the process. Application of 0.1 M HCl as the eluent enables effective desorption of precious metals and reuse of sorbent for purifying water solutions of Cu²⁺ and Cr³⁺ ions.     

Adsorption Kinetics of Toxic Heavy Metal Ions from Aqueous Solutions onto Grafted Jute Fibers with Acrylic Acid by Gamma Irradiation

Jute fibers were used as an adsorbent substrate for Hg²⁺ and Pb²⁺ metal ions as toxic pollutants from their aqueous solutions after graft copolymerization with polyacrylic acid under the effect of gamma irradiation. The treated jute fibers were characterized by using of Fourier-Transform Infrared Spectroscopy. The effects of solution pH, contact time, temperature, and the dissolved metal ions’ concentration on the adsorption efficiency were investigated. The adsorption kinetics and the used adsorption isotherm were also investigated. From the results, it was concluded that the adsorption process conformed the second-order kinetic reaction and followed the Langmuir adsorption isotherm model, and the higher adsorption capacities were at pH 5 and 6 for Pb²⁺ and Hg²⁺ metal ions respectively.     

Adsorption of Cu2+ by Crosslinked Graft Copolymers of Starch

With the use of acrylic acid(AA)as a monomer,humic acid(HA)and starch as raw materials,potassium persulfate(KPS)as initiator,and N,Ndimethylacrylamide(MBA)as a cross-linking agent,AA/HA/Starch graft copolymer was prepared and characterized by SEM and FT-IR.The effects of temperature,adsorption time,adsorbent dosage,pH value and Cu²⁺initial concentration of the solution on the adsorption performance of the crosslinked graft copolymer were also investigated.The results showed that the Cu²⁺adsorption capacity of the AA/HA/Starch graft copolymer increased firstly and then decreased with increasing adsorbent dosage and the initial pH value of Cu²⁺solution.With the increase of Cu²⁺initial concentration and the extension of adsorption time,the adsorption amount of Cu²⁺increased rapidly and then stabilized.And it decreased slightly with the increase of temperature.At pH value of 5.5,temperature of 298 K,adsorbent dosage of 50 mg,adsorption time of 125 min,and 100 mL Cu²⁺solution with Cu²⁺initial concentration of 100 mg/L,the Cu²⁺adsorption capacity of the crosslinked graft copolymer was 238 mg/g.The adsorption of Cu²⁺by the adsorbent followed the pseudo-second-order kinetic equation and Langmuir isothermal adsorption model,and the adsorption was attached to monolayer chemical adsorption.This study proved that AA/HA/Starch graft copolymer could be used as an efficient adsorbent for the removal of harmful and toxic metal cations such as Cu²⁺from industrial wastewater.     

Agave sisalana,a biosorbent for the adsorption of Reactive Red 120 from aqueous solution

The textile industry is one of the largest producers of dye effluent. Treatment of these effluents has to be cost effective hence a number of precursors have been studied as a viable alternative adsorbent. Sisal fibre was converted to activated carbon by chemical methods. Sisal fibre was activated with different activating agents such as H₃PO₄, HCl, HNO₃, NaOH and KOH. The adsorption of Reactive Red 120 (RR 120) dye onto sisal fibre activated carbon (SFAC) from aqueous solution was investigated. Adsorption experiments were carried out at different dye concentrations, initial solution pH and carbon dosage. Batch adsorption studies were carried out using activated carbon produced using phosphoric acid yielded better carbon as it good results in terms of Methylene Blue number and Iodine number. These carbons were used to study the batch adsorption studies. Methylene Blue number and Iodine number of SFAC were found to be 240 mg/g and 855 mg/g, respectively. The BET surface area of the carbon was 885 m²/g. The batch experiments adsorption isotherm studies fitted well to Langmuir isotherm and the adsorption capacity was found to be 110 mg/g. Adsorption kinetics data were tested using pseudo-first-order and pseudo-second-order models. Kinetic studies showed that the adsorption data followed a pseudo-second-order reaction.     

The biosorptive effect of untreated and chemically modified fir cone powder on Pb(II) removal

In this work, the main aim was to investigate the adsorption potential of untreated and chemically modified (sodium hydroxide and hydrogen peroxide treatment) fir cone powder (Abies alba) for the removal of Pb(II) from aqueous solutions. The effect of contact time, initial concentration of Pb(II), initial pH and temperature was studied in a batch process mode. Adsorption isotherm models (Langmuir, Freundlich, Dubinin–Radushkevich (D–R) and Temkin) and kinetics (pseudo-first-order and pseudo-second-order) models for both processes (treated and untreated) were used to analyse the equilibrium data. The kinetic data were found to fit better the pseudo-second-order. Maximum adsorption capacities calculated using the Langmuir model are 4.8 and 2.9 mg/g for NaOH and H₂O₂ treated fir cone powder, respectively, and 3.7 mg/g for untreated fir cone powder. The results indicate that the NaOH treatment increases the fir cone powder adsorption capacity, while the H₂O₂ treated biomass showed a slight decrease in its adsorption capacity in comparison to the untreated one.     

离子交换纤维对糖液中钙离子的脱除

研究了强酸离子交换纤维对糖液中钙离子的吸附动力学和吸附等温线。试验表明 ,纤维对糖液中钙离子的吸附速度明显快于 732型树脂。吸附平衡等温线符合Langmuir方程。糖液操作流速在 4mL/min以内时 ,纤维动态吸附速度也很快 ,且糖液浓度对吸附速度影响较小 ,动态饱和吸附量可达 47mg/g干纤维。该纤维可用于糖液的除钙。     

Modified barley straw as a potential biosorbent for removal of copper ions from aqueous solution

Barley straw (BS), a very low-cost material, has been utilized as a biosorbent material for the removal of copper (Cu²⁺) ions from aqueous solutions after treatment with citric acid. Barley straw was thermochemically modified with citric acid (CA–BS) for the purpose of improving the Cu²⁺ ion sorption capacity of the straw. Biosorption studies have been carried out to determine the effect of pH, adsorbent concentration, contact time, extent of modification, and adsorbate concentration on the biosorption capacity of Cu²⁺ ions by the esterified straw. The equilibrium sorption capacities of Cu²⁺ were 4.64 mg/g and 31.71 mg/g for BS and CA–BS, respectively. The optimum pH for the removal of Cu²⁺ ions by CA–BS was around pH 7.0 and the removal of Cu²⁺ ions was 88.1%. Langmuir, Freundlich, Scatchard and D–R (Dubinin–Radushkevich) isotherms have been used to characterize the observed biosorption phenomena of Cu²⁺ ions on CA–BS. The carboxyl groups on the surface of the modified barley straw were primarily responsible for the sorption of Cu²⁺ ions.     

Sawdust of lam tree (Cordia africana) as a?low-cost, sustainable and easily available adsorbent for the removal of toxic metals like Pb(II) and Ni(II) from aqueous solution

Sawdust of lam tree (Cordia africana) has been investigated as an adsorbent for the removal of lead and nickel ions from aqueous solution. Since lam tree is widely grown in almost all the eastern, western, central and southern tropical African countries (United States Department of Agriculture, GRIN, Maryland), it can be a?common most easily available, sustainable, low cost adsorbent for the treatment of wastewaters in this part of the world where growing industrialization is affecting water quality like elsewhere in the world. Therefore, it is worthwhile to investigate the potential of sawdust of lam tree as an adsorbent for the removal of lead and nickel ions from aqueous solution as a?first step. The effect of contact time, pH, metal ion concentration and temperature on adsorption of these metal ions has been investigated to identify the optimum conditions for maximum adsorption. The equilibrium time was found to be 50?min for Pb⁺⁺ and 70?min for Ni⁺⁺ adsorption. Adsorption starts at a?low pH and increases steadily as the pH increases. The equilibrium adsorption data at temperatures of 25, 40 and 60°C were analyzed by the Langmuir and Freundlich isotherm models. Although equilibrium adsorption data conforms to both the models, the best fit was obtained with the Langmuir isotherm. Thermodynamic parameters like equilibrium constant, enthalpy change, free energy change, and entropy change were calculated and discussed. The maximum adsorption capacity of sawdust for Pb⁺⁺ and Ni⁺⁺ were calculated from the Langmuir isotherms. The metal uptake was found to increase with increase in temperature. The positive values of ??H ^o and negative values of ??G ^o together indicate that the adsorption of Pb⁺⁺ and Ni⁺⁺ on sawdust of lam tree is endothermic and spontaneous in nature. The study demonstrated that the sawdust of lam tree can be effectively used as an adsorbent for the removal of metal ions from aqueous solutions.     

Removal of Pb(II) from aqueous solutions by carbons prepared from Sal wood (Shorea robusta)

In the present work, physically and chemically activated carbons are prepared using Sal wood (Shorea robusta) sawdust by thermal process and using sulfuric acid as the activation agent to remove Pb(II) from aqueous solutions. Adsorption equilibrium studies have been done at a pH of 4 and a room temperature of 30 °C. It was found that the adsorption isotherms are favorable and chemically activated carbons are better than physically activated carbon in terms of adsorption capacity. Various two-parameter adsorption isotherm models, viz. Freundlich, Langmuir, Temkin and Dubinin-Radushkevich, were used to fit the equilibrium data and it was found that the Freundlich adsorption model provided best-fit. The first-order irreversible unimolecular reaction model and the pseudo-second-order kinetic models were used to fit the kinetic data and it was found that both the models provided good fit. Kinetic and film diffusion studies show that the adsorption of lead(II) on the activated carbons tested in this work are both intra-particle and film diffusion controlled.     

Adsorption kinetics,thermodynamics and isotherm of Hg(II) from aqueous solutions using buckwheat hulls from Jiaodong of China

The adsorption kinetics and adsorption isotherms of buckwheat hulls in the region of Jiaodong, China (BHJC) for Hg(II) were investigated. Results revealed that the adsorption kinetics of BHJC for Hg(II) were well described by a pseudo second-order reaction model, and the adsorption thermodynamic parameters ΔG, ΔH and ΔS were –5.83 kJ mol^?1(35 °C), 73.1, and 256 J K^?1 mol^?1, respectively. Moreover, Langmuir, Freundlich and Redlich–Peterson isotherm models were applied to analyse the experimental data and to predict the relevant isotherm parameters. The best interpretation for the experimental data was given by the Langmuir isotherm equation, and the maximum adsorption capacity for Hg(II) is 243.90 mg/g at 35 °C. Furthermore, investigation of the adsorption selectivity showed that BHJC displayed strong affinity for mercury in the aqueous solutions and exhibited 100% selectivity for mercury in the presence of Zn(II) and Cd(II).     

Preparation of Polysulfonamide Porous Paper and Its Adsorption Properties

Three-dimensional porous paper was prepared by using polysulfonamide (PSA) fiber and pulp as the raw materials. The effect of PSA fiber to pulp ratios on the mechanical strength and adsorption properties (using methyl orange and rhodamine B dyes in their aqueous phase) of the paper were studied. The results showed that the tensile strength and elongation characteristics decreased as the PSA fiber to pulp ratio increased, while the tear strength increased. PSA paper showed good adsorption performance for both methyl orange and rhodamine B, with the adsorption process conforming to the pseudo-second-order and Langmuir isotherm models, indicating monolayer chemical adsorption. The study has provided an improved theoretical and scientific basis for the further development and application of PSA paper.     

改性柚皮纤维素对Pb2+的吸附动力学研究

以柚皮为原料制备柚皮纤维素,并在一定条件下,与琥珀酸酐反应制取改性纤维素吸附剂(Cell 5 和Cell 6),用于吸附水溶液中的Pb2+,研究改性柚皮纤维素对Pb2+ 的吸附平衡和吸附动力学特性。结果表明：Cell 5 和Cell 6对Pb2+ 的吸附符合动力学二级反应,生物吸附作用遵循Langmuir 等温吸附方程,Cell 5 和Cell 6 的最大吸附量分别达到142.86mg/g 和181.82mg/g。     

Application of NaOH-HCl-Modified Apple Pomace to Binding Epigallocatechin Gallate

NaOH-HCl-modified apple pomace was prepared in order to increase the adsorption capacity for epigallocatechin gallate (EGCg). The modified apple pomace contained 408.2 mg g^?1 dietary fiber, 57.7 mg g^?1 lignin, 23.2 mg g^?1 protein, and 9.0 mg g^?1 pectin, and the features of the apple pomace materials were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The adsorption of EGCg onto modified apple pomace showed excellent fitness with the pseudo-second-order model, suggesting that chemisorption was the rate-controlling step. The isothermal adsorption studies were carried out over a range of concentrations (25–1000 mg L^?1) and temperatures (20, 30, and 40 °C). Low temperature advanced the adsorption capacity for EGCg. Both the Langmuir and Freundlich models precisely described the isothermal adsorption of EGCg onto modified apple pomace. Thermodynamics showed that this adsorption process was endothermic and spontaneous. Our study highlights that NaOH-HCl-modified apple pomace has good adsorption characteristics for EGCg, which could be a promising candidate for EGCg delivery in functional food and dietary supplement applications.     

罗非鱼鱼鳞处理含铜废水

通过吸附实验考察Cu²⁺初始质量浓度、溶液pH、时间等因素对罗非鱼鱼鳞吸附水中Cu²⁺性能的影响;通过FTIR、BET、SEM、吸附动力学和吸附等温线分析吸附机理。结果表明:当溶液pH为5、温度为25℃、吸附剂用量为3 g/L、吸附时间为3 h、Cu²⁺初始质量浓度为100 mg/L时吸附效果最好,Cu²⁺的吸附率可达79.82%,吸附量可达26.63 mg/g;鱼鳞对Cu²⁺的吸附过程符合准二级动力学模型,为化学吸附;吸附等温线符合Langmuir吸附等温式。     

Adsorptive Removal of Patulin from Apple Juice Using Ca‐Alginate‐Activated Carbon Beads

This study aimed to investigate the adsorption of patulin from apple juice by Ca‐alginate‐activated carbon (Ca‐alginate‐AC) beads. The capacity of patulin was determined by high‐performance liquid chromatography. The results showed that Ca‐alginate‐AC beads have significant ability to reduce patulin from contaminated apple juice. Furthermore, the adsorption process did not affect the quality of apple juice. The effects of contact time, initial patulin concentration, adsorbent dose, and temperature were assessed. The removal percentage of patulin increased with contact time, adsorbent dose, and temperature. A reduction was also noted to bind patulin at increased levels of contamination. The equilibrium data were fitted to Langmuir, Freundlich, and Temkin isotherm models and the isotherm constants were calculated at different temperatures. The adsorption equilibrium was best described by the Freundlich isotherm (R² > 0.990). The pseudo 1st‐order model was found to describe the kinetic data satisfactorily. Thermodynamic parameters such as standard Gibbs free energy (ΔG??), standard enthalpy (ΔH?), and standard entropy (ΔS?) were evaluated. The results showed that the adsorption was spontaneous and endothermic nature.     

Heat-treated wood as chromium adsorption material

Heavy metals adsorption with lignocellulosic materials has been heavily researched in the last years. Since heat activation has been used with good results to increase the adsorption capacity of some materials, heat-treated wood might be a better adsorbent. This hypothesis is the basis of the present study. The adsorption tests were made with powdered pine wood, heat-treated at 190–210?°C. All the heat-treated samples showed a significantly higher adsorption compared to untreated wood. The maximum adsorption was obtained at pH 3 for heat-treated wood at 210?°C. The kinetics of the adsorption process fitted a pseudo-second-order reaction (R² 0.990–0.996). Adsorption fitted well both the Langmuir and the Freundlich model, but the Freundlich model presented higher R² (0.988–0.998). The q_max values estimated by the Langmuir plotting were in the range 15.6–19.4 mg/g and the n values from Freundlich isotherms between 1.87 and 2.39. Heat-treated wood was a better adsorption material than untreated wood for chromium adsorption. This can be a good application for the sawdust produced by the processing of heat-treated wood at primary and secondary wood processing mills or for the recycling of heat-treated wood at the end of product life.     

Extraction of Anthocyanins from Black Bean Canning Wastewater with Macroporous Resins

This study investigated purification of anthocyanins from black bean canning wastewater by column chromatography with 5 types of macroporous resins (Diaion Hp20, Sepabeads Sp70, Sepabeads Sp207, Sepabeads Sp700, and Sepabeads Sp710). By‐product of canned black beans was partially purified by filtration, in anticipation of higher performance during column chromatography. Equilibrium adsorption isotherms were measured and analyzed using Langmuir and Freundlich isotherm models. Both Langmuir (all R² ≥ 0.98) and Freundlich (all R² ≥ 0.97) models can describe the adsorption process of anthocyanins from black bean canning wastewater using the tested resins. The adsorption and desorption behaviors of anthocyanins were studied using a dynamic method on the 5 types of resins, and Sp700 presented the highest adsorption capacity (39 ± 4 mg/g; P < 0.05) as well as desorption capacity (19 ± 2%; P < 0.05), indicating that of the resins examined, Sp700 is a better candidate for purification of anthocyanins from black bean canning wastewater.     

Adsorption of egg yolk plasma cholesterol using a hydrophobic adsorbent

Data on hydrophobic adsorption equilibrium of egg yolk plasma cholesterol were obtained using Streamline Phenyl^® resin in batch suspension at room temperature (25 °C). Influence of two types of salt (NaCl and Na₂SO₄) at four concentrations (0.0; 0.05; 0.1, and 0.2 M) on equilibrium was analyzed. Increased salt concentration reduced the amount of cholesterol adsorbed in the resin. Two isotherm models (Langmuir and a modified model based on type S-isotherm) were used to represent solid-liquid equilibrium data. The latter led to a better fit of the equilibrium data, with a 99.8% value of RSSE. A 70% reduction of the cholesterol content in the plasma was obtained with a 1:4 plasma:water dilution ratio.     

Preparative separation and purification of Rebaudioside A from Stevia rebaudiana Bertoni crude extracts by mixed bed of macroporous adsorption resins

The separation and purification of Rebaudioside A (RA) from Stevia rebaudiana Bertoni crude extracts (Steviosides) by macroporous adsorption resin (MAR) mixed bed were systematically investigated. MAR mixed bed of HPD750-LSA40-LSA30-DS401 was selected due to its better separation degree. Based on the kinetics/thermodynamics experiment of the mixed bed, it was found that the experimental data fitted better to the pseudo-second-order model, and intra-particle diffusion was rate-limiting step. The adsorption isotherm was consistent with IV equilibrium adsorption isotherm classified by Brunauer. Furthermore, the influencing factors for the separation of RA based on HPLC were also investigated. Under the optimal conditions, the separation degree for RA (D_AS) increased from 0.771 to 1.54. Moreover, the experimental results showed that the purity of the obtained product increased from 60% to 97%.