Efficiency of succinylated-olive stone biosorbent on the removal of cadmium ions from aqueous solutions

Chemical functionalization of olive stone wastes with succinate linkers can potentially improve the performance of wastewater treatment technologies via enhanced adsorption and high affinity of the covalently attached succinate groups for heavy metals. In this study, a novel reusable adsorbent material based on agricultural waste has been synthesized by esterifying the lignocellulosic matrix of olive stones with succinic anhydride in toluene under basic conditions. Characterization of the as-prepared material by FTIR and solid-state MAS ¹³C NMR spectroscopies and TGA confirmed that the heterogeneous esterification has proceeded very efficiently to yield the succinylated-olive stone (S–OS). Subsequent alkaline treatment of S–OS with saturated NaHCO₃ aqueous solution led to the resulting sodic material (NaS–OS), which was subjected to batch experiments in order to evaluate its cadmium-removing efficiency from aqueous solutions at realistic concentrations of cadmium found in industrial effluents. The results obtained from the sorption characteristics have revealed that NaS–OS material is highly effective in removing cadmium from aqueous solutions, with a maximum uptake capacity of 200 mg g⁻¹ (1.78 mmol g⁻¹). The Langmuir isotherm model was found to fit adequately the equilibrium isotherm data. Cadmium adsorption occurs rapidly and the adsorption mechanism is a chemical sorption via ionic exchange between the adsorbate and adsorbent. Thermodynamic parameters were also evaluated from the effect of temperature studies. Regenerability of NaS–OS material was ascertained by quantitative desorption of cadmium with 1 M aqueous NaCl and the reusability of the matrix after five repeated cycles led to nearly no attenuation in its performance (less than 2% in the sorption capacity), indicating that repeated use of NaS–OS is quite feasible. Compared to other low-cost adsorbents utilized for the removal of Cd(II) from water/wastewater, NaS–OS shows higher sorption capacity. These results have important implications for the design of low-cost adsorbents based on agricultural wastes.     

Circumventing possible inaccuracies of the single aliquot regeneration method for the optical dating of quartz

A simple method of assessing the reliability of the single aliquot regeneration method is presented, based on the repeated measurement of identical regeneration doses. It is shown that for the majority of the samples measured the requirement of a constant repeat point in each cycle is not met. The ability to maintain a constant repeat point is shown to be dependent upon preheating conditions, the requirements for which were found to vary at both inter-sample and inter-aliquot levels. The expected effect on estimated values of D_e is calculated and shown to be significant. Three possible means of circumventing these inaccuracies are presented: (i) adjustment of the measurement procedure (specifically the preheat conditions); (ii) modelling and correcting for the effect, and (iii) stabilising the response prior to construction of the regenerated growth curve. It is suggested that much of the variation in D_e observed between individual aliquots and between individual grains from well-bleached sediments may possibly be attributed to differences in preheating requirements, and that such differences may also account for some of the spread in D_e for partially bleached sediments.     

Selective adsorption of phosphate in water using lanthanum-based nanomaterials: A critical review

In recent years, lanthanum-based nanomaterials (La-NMs) are selected as an efficient nano-adsorbent for phosphate removal because La³⁺ has a strong affinity with oxygen-donor atoms from phosphate. Additionally, there are a broad interest and literature base for the effect of different synthesis optimization and environmental parameters on the adsorption performance of La-NMs. A considerable amount of research has also investigated the regeneration and application of La-NMs to real wastewater in a laboratory scale. Based on the literature survey, it was found that La-NMs are often produced via co-precipitation and hydrothermal methods. Moreover, phosphate's adsorption process and behavior onto La-NMs are described well with the pseudo-second-order model and Langmuir model. The interaction mechanism between phosphate and La-NMs are dominated by ligand exchange, surface complexation and electrostatic attraction. Furthermore, phosphate could easily desorb from La-NMs due to the weak H-bonding interaction between phosphate and the H-bond acceptor groups on the surface of La-NMs. Despite the wealth of literature available in this area, there is a lack of systematic review to evaluate the gaps in the use of La-NMs to eliminate phosphate in water. In this review, we mainly summarize and discuss the role and the effect of the synthesis techniques on the physicochemical properties and the adsorption behavior of La-NMs. The possible adsorption mechanism, regeneration efficiency, and the application of La-NMs to the real environmental samples are also presented and highlighted.     

碳纳米管-氧化铝:高抗硫及再生性能的Pt基催化剂载体及在NO_x还原反应中的应用(英文)

通过乙炔在Al2O3上的分解制备碳纳米管-氧化铝(Al2O3-CNTs)载体.采用浸渍法,分别制备了Pt/Ba/Al2O3-CNTs和Pt/Ba/Al2O3催化剂.利用XRD,SEM,TEM,低温N2物理吸附,XPS和in-situ DRIFTS等手段对催化剂的物化性质进行了表征.结果表明,在SO2存在下的NOx还原反应中,Pt/Ba/Al2O3-CNTs比Pt/Ba/Al2O3具有更高的抗SO2性能和再生性能.In-situ DRIFTS表明SO2的存在对NOx储存还原的途径没有影响.     

离子液体对锯末中纤维素的溶解及再生研究

探讨了离子液体1-(4-磺酸基丁基)-3-甲基咪唑的硫酸氢盐(IL-1)作为催化剂,金属氯化物作为助催化剂时纤维素的水解,利用离子液体IL-1对杨木锯末中纤维素的直接溶解并再生,考察了温度、碱性溶液的浓度以及溶解时间对溶解率的影响,通过傅里叶红外光谱FT-IR、X-射线衍射仪及热失重对处理前后锯末、再生纤维素的结构、结晶性及热性能进行了研究.结果表明,温度为90℃,NaOH质量分数为6%,溶解时间为2 h时,离子液体对杨木锯末具有最佳的溶解性,溶解率可达45%左右.离子液体主要溶解杨木锯末中的纤维素,且为非衍生化的直接溶解,再生后的纤维素结晶形态由纤维素I变为II,热稳定性能有所降低.     

基于计时库仑技术的可再生型三磷酸腺苷适配体电化学传感器的研究

构建了一种可再生型三磷酸腺苷(ATP)适配体计时库仑电化学传感器.将一条短链DNA通过AuS键自组装固定在电极表面, ATP的核酸适配体与该短链DNA杂交而结合在电极表面.带负电的DNA通过静电吸引结合电解液中的六氨合钌(RuHex)阳离子.当传感器和靶分子ATP孵育后,ATP与核酸适配体结合,使适配体链从电极表面解离,电极表面吸附的DNA量减少,结合RuHex的量随之降低.通过计时库仑技术检测RuHex响应信号降低的量 ,可以对ATP进行定量测定.此传感器的电化学响应信号与ATP浓度对数值呈线性关系,线性检测范围为0.001~100 μmol/L,检出限(S/N=3)为0.5 nmol/L.此传感器检测靶分子ATP后,可以通过简单的操作步骤再生,再生5次后的响应信号为初始信号的90%以上.采用此传感器检测大鼠脑透析液中ATP的含量为(19.2±3.7) nmol/L (n=3).     

Preparation of magnetic chitosan and graphene oxide-functional guanidinium ionic liquid composite for the solid-phase extraction of protein

A series of novel cationic functional hexaalkylguanidinium ionic liquids and anionic functional tetraalkylguanidinium ionic liquids have been synthesized, and then magnetic chitosan graphene oxide (MCGO) composite has been prepared and coated with these functional guanidinium ionic liquids to extract protein by magnetic solid-phase extraction. MCGO-functional guanidinium ionic liquid has been characterized by vibrating sample magnetometer, field emission scanning electron microscopy, X-ray diffraction spectrometer and Fourier transform infrared spectrometer. After extraction, the concentrations of protein were determined by measuring the absorbance at 278 nm using an ultra violet visible spectrophotometer. The advantages of MCGO-functional guanidinium ionic liquid in protein extraction were compared with magnetic chitosan, graphene oxide, MCGO and MCGO-ordinary imidazolium ionic liquid. The proposed method has been applied to extract trypsin, lysozyme, ovalbumin and bovine serum albumin. A comprehensive study of the adsorption conditions such as the concentration of protein, the amount of MCGO-functional guanidinium ionic liquid, the pH, the temperature and the extraction time were also presented. Moreover, the MCGO-functional guanidinium ionic liquid can be easily regenerated, and the extraction capacity was about 94% of the initial one after being used three times.     

Adsorption of cadmium(II) in wastewater by magnesium oxide modified biochar

A new MgO-AC (magnesium oxide modified activated carbon) adsorbent was successfully synthesized under microwave irradiation. XRD, FT-IR, XPS, SEM and N₂ adsorption were used to characterize the properties of MgO-AC. It was found that MgO-AC was highly crystalline under the preparation process, and the doping of MgO (Magnesium oxide) did not cause the gap blockage of AC (activated carbon), but the micropore area and average pore size of modified AC increased significantly. Multiple conditional parameters were studied to determine the optimal adsorption effect, such as roasting temperature, holding time, MgO doping amount, contact time, adsorption temperature, system pH, and initial concentration of Cd(II) (divalent cadmium ion). The results show that the optimal parameter conditions are as follows: the insulation temperature is 800 °C, holding time of 40 min, the doping amount of MgO is 1/20 of AC, and the maximum adsorption capacity is 649.9 mg·g^?1 at pH = 7. In addition, thermodynamic studies show that the adsorption process is spontaneous and endothermic, and kinetic and adsorption isotherm models show that the pseudo-second-order kinetic model and Langmuir model are well fitted for the adsorption process.     

Polystyrene electrospun nanofibers as effective sorbents for the removal of atypical antipsychotics: Kinetic and thermodynamic studies

In this study, polystyrene nanofibers were prepared by electrospinning for the adsorption of olanzapine, risperidone, and clozapine from aqueous solution. The properties of polystyrene nanofibers were characterized via FTIR, SEM, TEM, TG, and XRD analyses. In addition, the impact of contact time, initial ion concentration, adsorbent dosage, temperature, and pH on the adsorption was studied. The adsorption kinetics and thermodynamic evaluation of three analytes on PS nanofibers were performed. The adsorption of the three analytes by polystyrene nanofibers followed the first-order kinetics with constant rates of 0.02348, 0.02683, and 0.03024 mg/g min for olanzapine, risperidone, and clozapine, respectively. Further, the adsorption conformed to Redlich-Peterson isotherm model and the maximum adsorption capacities for olanzapine, risperidone, and clozapine were 12.33, 8.36, and 12.96 mg/g, respectively. The adsorption process was characterized by spontaneous, exothermic, and physical reaction. The regeneration of nanofiber adsorbent showed that the adsorption capacity did not significantly change after 5 cycles of desorption. The selectivity of different analytes followed the order of clozapine > risperidone > olanzapine. Thus, the polystyrene electrospun nanofibers exhibit good potential as novel adsorbents for the isolation and purification of antipsychotic drugs from biological samples.     

Synthesis and application of treated activated carbon for cationic dye removal from modelled aqueous solution

Use of activated carbon (AC) prepared from rice husk and treated with anionic surfactant is investigated to eliminate cationic dye crystal violet (CV) using modelled dye solution. AC modified with anionic surfactant sodium lauryl sulfate (ACSLS) and other two surfactant namely sodium dodecyl sulfonate and hexadecyl trimethyl ammonium bromide were used for the analysis. Optimum ACSLS was analyzed and characterized using BET, XRD, SEM accompanied with XEDS, FTIR, HR-TEM and zeta potential, which confirms the sorption of CV onto ACSLS. Influence of pH, dose of adsorbent, concentration of initial dye, contact time, additive salts as well as actual water samples were investigated. Presence of NH⁴⁺, Ca²⁺, Mg²⁺, Na²⁺, Ca²⁺ and K⁺ cations in dye solution were having negligible (less than 4 %) influence on dye removal capacity. Study of mass transfer parameters revealed intra particle diffusion and film diffusion both played their part, whereas other kinetic studies has shown that experimental data fitted best with Pseudo 2nd order rate. Isotherm studies accompanied with error analysis revealed that Langmuir isotherm controls the adsorption equilibrium with highest capacity of CV adsorption with optimum operating conditions as pH = 6, temperature = 318 K, adsorbent dose = 100 mg/L and dye concentration = 30–60 mg/L. Study of thermodynamics and temperature analysis have shown that the sorption reaction was favourable and spontaneous with rise in temperature and endothermic in nature. Column studies are reported for varying rate of flow, depth of bed and dye concentrations along with analysis of column experimental data with various models like Yoon-Nelson, Thomas, Bohart-Adam and Clark model. Reusability (no. of cycles) of used adsorbent was studied using regeneration experiments. Analysis inferred that AC modified using surfactants can be a useful technique for enhanced adsorption capacity of dyes from aqueous solution and not much work has been reported on use of anionic surfactant modified AC for dye removal process.