Removal of C.I. acid brown 75 from aqueous solution by kaolinite

The adsorption of acid brown 75 onto kaolinite in aqueous solution was studied with respect to the pH, adsorbent dosage, contact time, initial concentration, and operating temperature. Desorption of dye from dye-saturated kaolinite was observed. Experimental data indicated that the adsorption capacity of kaolinite for the dye was higher in acidic rather than in basic solution. The maximum adsorption capacity of kaolinite towards the dye was found to be 96.5 mg g^?1 (pH 1.0). At the optimal adsorption condition, the dye removal ratio was 95.5%. Dye-saturated kaolinite could desorb at aqueous NaOH, the desorption ratio of dye was 78.8%. The linear Langmuir and Freundlich isotherm models are well fitting to represent the experimental data.     

Equilibrium studies on the adsorption of acid dye into chitin

We report the adsorption isotherm of acid dye on the surface of chitin, a unique solid adsorbent. Adsorption process offers an attractive benefit for a dyeing house treatment. Influences of essential kinetic parameters such as adsorbent particle size, reaction temperature governing the dye adsorption have been investigated. Adsorptions isotherms of dye on chitin were developed and the equilibrium data fitted well to the Langmuir, Freundlich and Redlich Peterson isotherm model. At optimum conditions maximum dye adsorption capacity of chitin estimated with the Langmuir 44.0, 85.0, 104.3 mg/g and 85.0, 114.10, 113.62 mg/g adsorbent. The results showed that chelating polymer of chitin could be considered as potential adsorbents for acid dye removal from dilute solution.     

Adsorption of humic acid from aqueous solution on bilayer hexadecyltrimethyl ammonium bromide-modified zeolite

Surfactant-modified natural zeolites (SMNZ) with different coverage types were prepared by loading hexadecyltrimethyl ammonium bromide (HTAB) onto the surface of a natural zeolite. The adsorption behavior of humic acid (HA) on SMNZ was investigated. Results indicate that the adsorbent SMNZ exhibited a higher affinity toward HA than the natural zeolite. HA removal efficiency by SMNZ increased with HTAB loading. Coexisting Ca²⁺ in solution favored HA adsorption onto SMNZ. Adsorption capacity decreased with an increasing solution pH. For typical SMNZ with bilayer HTAB coverage, HA adsorption process is well described by a pseudo-second-order kinetic model. The experimental isotherm data fitted well with the Langmuir model. Calculated maximum HA adsorption capacities for SMNZ with bilayer HTAB coverage at pH 5.5 and 7.5 were 63 and 41 mg·g^-1, respectively. E2/E3 (absorbance at 250 nm to that at 365 nm) and E4/E6 (absorbance at 465 nm to that at 665 nm) ratios of the residual HA in solution were lower than that of the original HA solution. This indicates that the HA fractions with high polar functional groups, low molecular weight (MW), and aromaticity had a stronger tendency for adsorption onto SMNZ with bilayer HTAB coverage. Results show that HTAB-modified natural zeolite is a promising adsorbent for removal of HA from aqueous solution.     

Preparation of a novel anion exchange group modified hyper-crosslinked resin for the effective adsorption of both tetracycline and humic acid

A novel hyper-crosslinked resin (MENQ) modified with an anion exchange group was prepared using divinylbenzene (DVB) and methyl acrylate (MA) as comonomers via four steps: suspension polymerization, post-crosslinking, ammonolysis and alkylation reactions. The obtained resin had both a high specific surface area (793.34 m²·g^-1) and a large exchange capacity (strong base anion exchange capacity, SEC: 0.74 mmol·g^-1, weak base anion exchange capacity, WEC: 0.45 mmol·g^-1). XAD-4 was selected as an adsorbent for comparison to investigate the adsorption behavior of tetracycline (TC) and humic acid (HA) onto the adsorbents. The results revealed that MENQ could effectively remove both TC and HA. The adsorption capacity of XAD-4 for TC was similar to that of MENQ, but XAD-4 exhibited poor performance for the adsorption of HA. The adsorption isotherms of TC and HA were well-fitted with the Freundlich model, which indicated the existence of heterogeneous adsorption through cation-π bonding and π–π interactions. The optimal solution condition for the adsorption of TC was at a pH of 5–6, whereas the adsorption of HA was enhanced with increasing pH of the solution.     

聚苯乙烯树脂吸附水中磺基水杨酸的研究

研究了两种聚苯乙烯树脂对水中磺基水杨酸的吸附行为,同时探讨了氨基修饰聚苯乙烯树脂的吸附动力学特性．结果表明,在所研究的磺基水杨酸浓度范围内,Langmuir和Freundich吸附等温方程都能很好地描述吸附平衡数据．采用氨基修饰制备的NDA-900树脂具有较大的吸附容量和较快的吸附速率,吸附动力学符合Lagergren二级速率方程,颗粒内扩散是NDA-900树脂吸附磺基水杨酸速率的主要控制步骤,可采用HSDM模型加以描述．     

Adsorptive behaviors of humic acid onto freshly prepared hydrous manganese dioxides

This study focused on the adsorptive behaviors of humic acid onto freshly prepared hydrous MnO₂(s) (δMnO₂), and investigated the feasibility of employing δMnO₂ for humic acid removal from drinking water. Effects of such parameters as molecular mass of humic acid, kinds of divalent cations on adsorptive behaviors and possible mechanisms involved were investigated. This study indicated that humic acid with higher molecular mass exhibited more tendency of adsorbing onto δMnO₂ than that with lower molecular mass. Ca²⁺ facilitated more humic acid adsorption than Mg²⁺; UV-Vis spectra analysis indicated higher capabilities of Ca²⁺ coordinating with acidic functional groups of humic acid than that of Mg²⁺. Additionally, ζ potential characterization indicated that Ca²⁺ showed higher potential of increasing gz potential of δMnO₂ than Mg²⁺. Ca²⁺ of 1.0 mmol/L increased ζ potential of δMnO₂ from ?37 mV (pH 7.9) to +7 mV (pH 7.2), while 1.0 mmol/L Mg²⁺ increased to lower value as ?9 mV (pH 6.5), correspondingly. Fourier transform infrared (FTIR) spectra demonstrated the adsorption of humic acid onto δMnO₂, showing the important roles of-COO^? functional groups and surface Mn-OH in the adsorption of humic acid onto δMnO₂.     

杭锦2~#土复合吸附剂对磷的吸附动力学

通过静态试验考察杭锦2#土/聚合硫酸铝复合吸附剂对生活污水中磷酸根的吸附特性,研究吸附过程的动力学模型,并从动力学角度探讨其吸附机理。结果表明,在杭锦2#土/聚合硫酸铝复合吸附剂用量5 g.L-1、吸附时间60 min、废水pH值6.0、温度25℃、磷初始质量浓度小于16.72 mg.L-1条件下,磷酸根的去除率在96%以上;复合吸附剂对磷酸根的吸附动力学特征符合假二级方程,吸附速率在前10 min为内扩散控制,后期由膜扩散和内扩散共同控制,且膜扩散占主导地位;磷酸根的初始浓度越高,吸附质粒子的表观内扩散系数和表观传质系数越小;使用不同再生次数的再生吸附剂（添加量为5 g.L-1）处理16.72 mg.L-1含磷生活污水,随着再生次数的增加,吸附能力有所下降,但磷酸根的去除率均大于89%。     

Experimental study of chromium adsorption on minerals in the presence of phthalic and humic acids

The effect of phthalic acid (benzene 1,2 dicarboxylic acid), a surrogate compound for natural organic matter, and of humic acid, on the adsorption of chromium to the surface of minerals was observed. In ternary systems involving phthalic acid, chromium(III) adsorption decreases on clays, probably because of aqueous Cr(III)-phthalate complexation, preventing ionic-exchange. Phthalic acid was also found to reduce chromium(VI) adsorption onto alumina, because of a competitive effect. In ternary systems involving humic acid, Cr(III) adsorption is increased in the low pH range because of the formation of surface ternary complex S-L-Cr(III) and is decreased in the high pH range because of aqueous Cr(III)-humate complexation.     

芳香酸稀溶液的络合萃取研究

络合萃取法分离极性有机物稀溶液具有高效性和高选择性。本文利用三辛胺或磷酸三丁酯为络合剂，四氯化碳、三氯甲烷、正辛醇或煤油为稀释剂，实验测定了苯甲酸、邻硝基苯甲酸稀溶液的萃取相平衡分配系数，讨论了影响因素。     

超高交联吸附树脂对水中对甲苯胺的吸附热力学与动力学研究

研究了带有磺酸基的超高交联吸附树脂NG-5和NG-10对水中对甲苯胺的静态吸附性能,并与不带磺酸基的CHA-111吸附树脂进行了比较．结果表明,NG-5树脂对水溶液中对甲苯胺的吸附能力高于NG-10及CHA-111,这主要得益于树脂表面的磺酸基与对甲苯胺分子的氨基间形成的氢键作用,以及树脂的微孔作用机制．吸附等温线采用三参数多层吸附方程来拟合,相关性很好．对吸附热力学和动力学的研究结果表明,NG-5和NG-10对于对甲苯胺的吸附为吸热过程,而且是自发进行的,吸附速率主要由颗粒内扩散控制．     

Removal of clofibric acid from aqueous solution by polyethylenimine-modified chitosan beads

Polyethylenimine （PEI）-modified chitosan was prepared and used to remove clofibric acid （CA） from aqueous solution. PEI was chemically grafted on the porous chitosan through a crosslinking reaction, and the effects of PEI concentration and reaction time in the preparation on the adsorption of clofibric acid were optimized. Scanning electron microscopy （SEM） showed that PEI macromolecules were uniformly grafted on the porous chitosan, and the analysis of pore size distribution indicated that more mesopores were formed due to the crosslinking of PEI molecules in the macropores of chitosan. The PEI-modified chitosan had fast adsorption for CA within the initial 5 h, while this adsorbent exhibited an adsorption capacity of 349 mg· g^-1 for CA at pH 5.0 according to the Langmuir fitting, higher than 213 mg· g^-1 on the porous chitosan. The CA adsorption on the PEI- modified chitosan was pH-dependent, and the maximum adsorption was achieved at pH 4.0. Based on the surface charge analysis and comparison of different pharmaceu- ticals adsorption, electrostatic interaction dominated the sorption of CA on the PEI-modified chitosan. The PEI- modified chitosan has a potential application for the removal of some anionic rnicropollutants from water or wastewater.     

不同炭化温度下烧制的竹炭对邻氯酚的吸附

研究了pH、吸附时间、竹炭投加量、邻氯酚初始浓度和吸附温度对不同炭化温度(500℃、700℃和900℃)下烧制的竹炭对邻氯酚的吸附特性的影响.结果表明,低pH值有利于3种竹炭对邻氯酚的吸附,其平衡吸附量均随初始浓度和吸附温度增大而增加,相同条件下,吸附量的大小依次为q900℃q500℃q700℃;500℃和700℃炭化温度下烧制的竹炭对邻氯酚的吸附表现出相似的变化规律,吸附时间为13h时基本达到平衡,而900℃炭化温度下烧制的竹炭的吸附则是一个快速吸附过程,30min内即达到吸附平衡;3种竹炭对邻氯酚的吸附皆是一个吸热过程,实验进行的吸附温度下,其吸附量的大小依次为q40℃q25℃q15℃.     

Removal of sulfadiazine from aqueous solution on kaolinite

The adsorption of sulfadiazine onto kaolinite clay as an alternative adsorbent was examined in aqueous solution, hnpacts of the contact time, pH, temperature, ionic strength and coexistent surfactants on the adsorption process were evaluated. The pH significantly influenced the adsorption process, with adsorption being promoted at lower pH due to the cation exchange mechanism. Decreasing ionic strength in the solution was favorable for adsorption, and the addition of cationic and anionic surfactants had negative effects on the adsorption capacity of sulfadiazine on kaolinite. Kinetic experiments showed that the adsorption followed the pseudo-second-order model. The equilibrium adsorption was well described by both Freundlich and Dubinin-Radushkevich （DR） models. According to the DR model, the adsorption mechanism was determined by cationic exchange and weak physical forces. The thermodynamic study showed that sulfadiazine adsorption onto kaolinite was a sponta- neous and endothermic reaction.     

氨基苯甲酸稀溶液的络合萃取研究

本文利用三辛胺或磷酸三丁酯为络合剂，正辛醇或煤油为稀释剂，在不同的Ｐ则定了氨基本甲酸稀溶液的萃取相平衡分配系数，讨论了影响因素，提出了同时考虑络合萃取作用和物理萃取作用的平衡分配系数的表达式。     

富磷污泥生物炭去除水中Pb(Ⅱ)的特性研究

以城市污水厂富磷剩余污泥为研究对象,考察高温热解制备生物炭吸附剂对水中Pb(Ⅱ)的去除效果.研究表明,随着热解温度升高,制备的生物炭对Pb(Ⅱ)的吸附能力增强;在相同热解温度下,生污泥生物炭对Pb(Ⅱ)的吸附能力比消化污泥生物炭大.采用700℃热解1 h制备生污泥生物炭以研究对Pb(Ⅱ)吸附的影响因素,结果显示:吸附180 min达到吸附平衡;富磷污泥生物炭对Pb(Ⅱ)的去除率随pH增加而升高;生物炭投加量增加,对Pb(Ⅱ)去除率上升,而单位吸附容量迅速减小.污泥生物炭对Pb(Ⅱ)的吸附符合准二级反应动力学,Langmuir模型比Freundlich模型能更好地拟合等温吸附线.在pH 5.0、吸附时间3 h、生物炭投加量20 g.L-1条件下,对Pb(Ⅱ)的最大吸附量为34.5 mg.g-1,表明富磷污泥生物炭可以作为一种廉价的吸附剂.     

Modeling of adsorption isotherms and kinetics of uranium sorption by magnetic ion imprinted polymers

Application of magnetic U(VI) ion imprinted polymers (IIPs) coated on magnetic nanoparticles was investigated for pre-concentration and determination of U(VI) ions in aqueous solutions. The scanning electron micrographs revealed the microporosity of the adsorbent. Uranium leaching was successful as the energy-dispersive X-ray spectra showed. The Brunauer–Emmett–Teller (BET) surface area improved by more than 13-fold (83.1 and 6.2 m² g^?1 for the leached and unleached magnetic IIP, respectively). U(VI) uptake was optimized using batch experiments with parameters affecting the uptake performance, such as initial uranium concentration, pH, contact time, and adsorbent dose investigated. Pseudo-second-order kinetics and the Langmuir isotherm model best fitted the experimental data. The maximum adsorption capacity of uranium onto the activated magnetic IIP reached 5.4 mg g^?1. The selectivity order was determined to be U(VI) > Ni(II) > Th(IV).     

Facile fabrication of dolomite-doped biochar/bentonite for effective removal of phosphate from complex wastewaters

● Dolomite-doped biochar/bentonite was synthesized for phosphate removal. ● DO/BB exhibited a high phosphate adsorption capacity in complex water environments. ● PVC membrane incorporated with DO/BB can capture low concentration phosphate. ● Electrostatic interaction, complexation and precipitation are main mechanisms. The removal of phosphate from wastewater using traditional biological or precipitation methods is a huge challenge. The use of high-performance adsorbents has been shown to address this problem. In this study, a novel composite adsorbent, composed of dolomite-doped biochar and bentonite (DO/BB), was first synthesized via co-pyrolysis. The combination of initial phosphate concentration of 100 mg/L and 1.6 g/L of DO/BB exhibited a high phosphate-adsorption capacity of 62 mg/g with a removal efficiency of 99.8%. It was also stable in complex water environments with various levels of solution pH, coexisting anions, high salinity, and humic acid. With this new composite, the phosphate concentration of the actual domestic sewage decreased from 9 mg/L to less than 1 mg/L, and the total nitrogen and chemical oxygen demand also decreased effectively. Further, the cross-flow treatment using a PVC membrane loaded with DO/BB (PVC-DO/BB), decreased the phosphate concentration from 1 to 0.08 mg/L, suggesting outstanding separation of phosphate pollutants via a combination of adsorption and separation. In addition, the removal of phosphate by the PVC-DO/BB membrane using NaOH solution as an eluent was almost 90% after 5 cycles. The kinetic, isotherm and XPS analysis before and after adsorption suggested that adsorption via a combination of electrostatic interaction, complexation and precipitation contributed to the excellent separation by the as-obtained membranes.     

Removal and recovery of uranium(VI) by adsorption onto a lignocellulosic-based polymeric adsorbent containing amidoxime chelating functional group

A new adsorbent (ABS) with amidoxime functional group was prepared through graft polymerization of acrylonitrile onto banana stem (BS) using ceric ammonium nitrate (CAN)/HNO₃ initiator system, followed by treatment with hydroxylamine hydrochloride in alkaline solution. Infrared spectroscopy, surface area analyzer, thermogravimetry, and potentiometric titration were used for the characterization of the adsorbent. Effective removal of U(VI) ions was demonstrated at the pH range 4.0–6.0. The mechanism for the removal of U(VI) ions by ABS was based on complexation adsorption model. Equilibrium was achieved in approximately 3 h. The experimental kinetic data were analyzed using first-order, second-order, and Elovich kinetic models, and are well fitted with second-order kinetics. The temperature dependence indicates an exothermic process. U(VI) adsorption was found to decrease with increase of ionic strength. The Freundlich isotherm model fitted the experimental equilibrium data well. The adsorption efficiency was tested using synthetic nuclear industry effluents. The maximum adsorption capacity for U(VI) removal was found to be 80 mg g^-1 at 20°C. Adsorbed U(VI) ions were desorbed effectively, about 99% by 0.2 M HCl. Repeated adsorption/desorption cycles show the feasibility of the ABS for the removal of U(VI) ions from water and nuclear industry effluents.     

Adsorption of cationic and anionic surfactants onto organic polymer resin Lewatit VPOC 1064 MD PH

The adsorption of a cationic (CTAB, cetyl trimethylammonium bromide) and an anionic surfactant (SLES, sodium dodecylethersulfate) from aqueous solution onto organic polymer resin (Lewatit VPOC 1064 MD PH) was studied. A series of batch experiments were performed to determine the sorption isotherms of surfactants to organic polymer resin. The experimental studies were analyzed by Langmuir and Freundlich isotherms. Furthermore, the isotherm parameters, average percentage errors (ε) of model data, and separation factor (R _L) were calculated. Other factors influencing the adsorption capacity (contact time, adsorbent amount, and initial surfactant concentration) were also discussed. The experimental data fitted very well to the Langmuir equilibrium model in the studied concentration range. The calculated R _L values showed that the adsorption of both surfactants were favorable. Among the surfactants, CTAB showed higher adsorption capacity onto organic polymer resin compared to SLES (Q ⁰ = 250 and 34.36 mg g⁻¹, respectively).     

Fabrication of magnetic multi-template molecularly imprinted polymer composite for the selective and efficient removal of tetracyclines from water

• Magnetic multi-template molecularly imprinted polymer composite was synthesized. • MIP composite was used as the adsorbent for removal of tetracyclines from water. • MIP composite showed excellent adsorption selectivity toward tetracyclines. • MIP composite possessed good reusability. Antibiotic contamination of the water environment has attracted much attention from researchers because of their potential hazards to humans and ecosystems. In this study, a multi-template molecularly imprinted polymer (MIP) modified mesoporous silica coated magnetic graphene oxide (MGO@MS@MIP) was prepared by the surface imprinting method via a sol-gel process and was used for the selective, efficient and simultaneous removal of tetracyclines (TCs), including doxycycline (DC), tetracycline (TC), chlorotetracycline (CTC) and oxytetracycline (OTC) from water. The synthesized MIP composite was characterized by Fourier transform infrared spectroscopy, transmission electron microscope and thermogravimetric analysis. The adsorption properties of MGO@MS@MIP for these TCs were characterized through adsorption kinetics, isotherms and selectivity tests. The MIP composite revealed larger adsorption quantities, excellent selectivity and rapid kinetics for these four tetracyclines. The adsorption process was spontaneous and endothermic and followed the Freundlich isotherm model and the pseudo-second-order kinetic model. The MGO@MS@MIP could specifically recognize DC, TC, CTC and OTC in the presence of some chemical analogs. In addition, the sorption capacity of the MIP composite did not decrease significantly after repeated application for at least five cycles. Thus, the prepared magnetic MIP composite has great potential to contribute to the effective separation and removal of tetracyclines from water.