Synthesis of a novel crosslinked superabsorbent copolymer with diazacyclooctadecane crown ether and its sorption capability

A novel crosslinked poly(acrylic acid-copolymer-Kryptofix-22-DM) superabsorbent copolymer, poly(AA-co-Kry22-DM), was synthesised by the reaction of 4,13-dimethylacryloyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (Kyrptofix-22-DM) and acrylic acid (AA). Characterisation of the polymers was achieved by FTIR and ¹H NMR techniques. Sorption capacity of the crosslinked poly(AA-co-Kry22-DM) superabsorbent copolymer was investigated for Pb²⁺, Cu²⁺, Cr³⁺, Cd²⁺, Mn²⁺, Zn²⁺, and Ni²⁺ heavy metal ions at different pH values using Freundlich and Langmuir isotherms. Swelling ratio, q_v, and distribution ratio, log D, values of the crosslinked poly(AA-co-Kry22-DM) superabsorbent copolymer were calculated at various pH values.     

Shellfish waste-derived mesoporous chitosan for impressive removal of arsenic(V) from aqueous solutions: A combined experimental and computational approach

Novel shellfish waste-derived chitosan (CS) has been developed to adsorb As(V) from simulated wastewater under evaluating adsorption process parameters. The coexistence of some competing ions, like SiO₃^2-, Cl^-, NO₃^– and PO₄^3- as well as the regeneration capacity of the spent adsorbent, was explored. The experimental data were modeled using several kinetics and isotherm models to understand the mechanism related to the uptake process. As(V) uptake was relatively rapid and highly dependent on pH. The Avrami-fractional-order expression supported data best, while the Liu equation described well isotherm data at pH 5.0. The maximum uptake capability (Liu) was 12.32 mg/g, and the highest removal performance (99 %) was obtained at optimum pH 5.0. Molecular dynamics simulations were performed to more clearly illuminate the atomic-level interactions between arsenic species and CS surface in both acidic and basic mediums. After four adsorption–desorption cycles, CS exhibited more than 90 % As(V) removal efficiency. The results of this study indicates that low cost shellfish derived chitosan is promising for efficient removal of As(V) from water body and can be used to remove other pollutants from watewater.     

Application of thermodynamics in a specific force field to the adsorption of Al ions on the chelating resins Ostsorb Oxin, Ostsorb Salicyl, Spheron Oxin, and Spheron Salicyl: Mathematical analysis of sorption isotherms using nonlinear mean square software

The sorption mechanism of Al³⁺ on chelating resins by means of mathematical analysis of sorption isotherms using nonlinear mean square software was studied. This method should yield more detailed information than classical thermodynamics and should be more flexible than the statistical-mechanical method, so that it would make it possible to obtain fairly easily relations directly applicable in practice. This model defined the specific potential Φ_Al^R for the ion in a resin (which depends on properties of resin and ion). On the basis of this model, N and PO isotherms were derived. To study the sorption mechanism, the Freundlich, Langmuir, N and PO equations (models) of isotherms were used. It was estimated that the functional groups (8-hydroxyquinoline and salicylate) in the studied chelating resins influence Φ_Al^R and thus their mechanism and sorption capacity.     

偕胺肟基功能高分子膜对铀吸附过程的研究

将在铝阴极表面电聚合的聚丙烯腈(PAN)涂层经偕胺肟基化反应(pH=7,70℃,3h)得到含有偕胺肟基的功能高分子膜(AFPF),PAN中的-CN基团有64.7%转化为-C(NH2)=N-OH,并研究了AFPF对硝酸铀溶液中的铀吸附性能.实验结果表明,AFPF对标准溶液中的铀吸附过程分为静电吸附和螯合吸附,且以后者为主,静电吸附的Freundlich等温方程为:гe=0.080c-0.66,螯合吸附的Freundlich等温方程为:гc=38.64c0.26,总吸附的Freundlich等温方程为:гt=38.21c0.26,并用扫描电镜表征了AFPF吸附铀前后的形貌.     

Hybrid of chitin and humic acid as high performance sorbent for Ni(II)

Hybrid of humic acid (HA) and chitin has been synthesized and the hybrid material (chitin-HA) was then applied as sorbent to adsorb Ni(II). The HA was extracted from peat soil of Gambut District, South Kalimantan, Indonesia, according to the procedure recommended by IHSS (International Humic Substances Society). The chitin was isolated from crab shell waste of sea food restaurants through deproteination using NaOH 3.5% (w/v) and followed by removal of inorganic impurities using HCl 1 M. The synthesis of chitin-HA was performed by reacting gelatinous chitin solution in HCl 0.5 M and HA solution in NaOH 0.5 M. Parameters investigated in this work consists of effect of medium acidity on the sorption, sorption rate (k_s) and desorption rate (k_d) constants, Langmuir (monolayer) and Freundlich (multilayer) sorption capacities, and energy (E) of sorption. The k_s and k_d were determined according to a kinetic model of first order sorption reaching equilibrium, monolayer sorption capacity (b) and energy (E) were determined according to the Langmuir isotherm model, and multilayer sorption capacity (B) was determined based on the Freundlich isotherm model.Sorption of Ni(II) on both chitin and chitin-HA was maximum at pH 8.0. The kinetic expression resulted from the proposed kinetic model has been shown to be more applicable than the commonly known Lagergren equation obtained from the pseudo-first order sorption model. The application of the proposed model revealed that the presence of HA increased the k_s from 0.018 min⁻¹ for chitin to 0.031 min⁻¹ for chitin-HA. As for k_s, the value of b was also bigger in the presence of HA, i.e. 7.42 × 10⁻⁵ mol/g for chitin and 9.93 × 10⁻⁵ mol/g for the chitin-HA. Unlike k_s and b, the value of E slightly decreased from 23.23 to 21.51 kJ/mol for the absence and presence of HA, respectively. It can also be deduced that the presence of HA on chitin contributed more to the additional layer of Ni(II) sorbed on sorbent. Without HA, B for chitin was only 6.17 times higher than b, while with the presence of HA, the enhancement of the sorption capacity from the multilayer (B) to the monolayer (b) was 19.40. The increase of k_s, b, B, and the decrease of E would be very benefit in the real application of chitin-HA for the recovery of Ni(II) from aqueous samples.     

Mathematical analysis of affinity membrane chromatography

A mathematical model including convection, diffusion and Freundlich adsorption is developed. To examine the validity of the model, the affinity membranes were prepared by coating chitosan on the nylon membranes, a ligand of poly-L-lysine was bound to the chitoan-coating membranes, and the adsorption behavior of bilirubin through the stacked affinity membranes was investigated. The agreements between the theoretical and experimental results are exceptional. Using our new model, we show that: (1) As Pe increases, the breakthrough curves become sharper. For Pe greater than 30, the effect of axial diffusion is insignificant; (2) As m increases, the time of total saturation is delayed and the loading capacity at the point of breakthrough is increased; (3) As n decreases, the time of total saturation is delayed and the loading capacity at the point of breakthrough is increased; (4) As r increases, both the time of total saturation and the loading capacity at the point of breakthrough are increased; (5) adsorption rate influences the time of total saturation strongly but contributes little to the loading capacity.     

Removal of Disperse Dyes from Aqueous Solution Using Sawdust and BDTDA‐Sawdust

The adsorption of two disperse dyes, disperse blue 56 and disperse red from aqueous solution onto sawdust (SD) and benzyldimethyltetradecyl ammonium (BDTDA) treated sawdust has been studied. The effect of initial concentration of dyes, pH, and contact time has been studied. The pH had a considerable influence on adsorption and optimum pH for adsorption of disperse dyes is found to be in the range of 2–3. The experimental data were analyzed using Langmuir and Freundlich adsorption isotherm equations. The experimental data were fitted well to pseudo first order kinetic model with R²>0.99. The results indicate that sawdust modified with surfactant can be employed as a low cost alternative to commercial activated carbon for the removal of disperse dyes.     

评Freundlich吸附等温式的推导

叙述了Freundlich吸附等温式的几种主要的推导方法,以及这些推导所反映的物理模型,并对它们进行了评价。     

Kinetic and theoretical studies of metal ion adsorption in KDP solution

Metal ion adsorption in saturated aqueous potassium dihydrogen phosphate solution was analyzed using kinetic, equilibrium model and computational chemistry approaches. The isotherm constants (K_F and n) in the Freundlich model and the first order Lagergren kinetic model parameter k assist with a general understanding of the fundamental adsorption behavior of trivalent and divalent metal ions. The electrostatic force based on electrostatic potential distribution was found to be an essential feature for metal ion adsorption via a correlation between the ESP values of each metal ion and these experimental parameters.     

Removal of Phenol from Wastewater Using Date Seed Carbon

The adsorption of phenol on Date Seed Carbon (DSC) was investigated to assess its possible use as an adsorbent for the processing of phenolic wastewater. The influence of various factors such as initial concentration, agitation speed, amount of adsorbent and temperature on the adsorption capacity has been studied. The percentage removal of phenol was observed to increase with increase an initial concentration of phenol. The adsorption of phenol decrease with an increase in temperature indicated the exothermic nature of the reaction. The Langmuir and Freundlich equations interpret adsorption isothermal data. Kinetic data was obtained by using a pseudo‐second‐order equation to understand the reaction mechanism. Thermodynamic parameters such as ΔG, ΔH and ΔS for the adsorption process were calculated.