Column Adsorption Experiments Research Articles

Amorphous Mn-La oxides immobilized on carbon sphere for efficient removal of As(Ⅴ), Cd(Ⅱ), and Pb(Ⅱ): Co-adsorption and roles of Mn species

Simultaneous removal of cation (e.g., Pb(Ⅱ), Cd(Ⅱ)) and oxyanion (e.g., As(Ⅴ)) heavy metals have attracted increasing interest for adsorption applications due to the complexity of heavy metal polluted groundwater. Manganese-lanthanum binary oxides immobilized on hydrothermal carbonization carbon (MnxLa1-x@HTCC) were therefore rationally designed in this work, and the Mn-La oxides immobilized on HTCC exhibited more uniform dispersion compared to bulk phase. In single adsorption systems, superior adsorption of different heavy metals could be achieved by tuning the molar ratio of Mn to La, and Mn leaching was reduced by ∼ 75% compared with Mn@HTCC (without La doping). In the coexisting systems, the simultaneous presence of As(Ⅴ) and Pb(Ⅱ) greatly enhanced adsorption of both two heavy metals, while competition was observed in the coexistence of As(Ⅴ) and Cd(Ⅱ). By analyzing the “release-readsorption” phenomenon of Mn and the variation of Mn valence during adsorption, the different roles of Mn species in the removal of three heavy metals were proposed. Finally, high-speed flow adsorption column experiments confirmed that the MnxLa1-x@HTCC composite can effectively and continuously adsorb heavy metals accompanied by trace Mn leaching content. Overall, this study indicates the potential of Mn-La carbon composites as a novel adsorbent in groundwater remediation.

Synthesis and application of recyclable core‐shell structure microspheres MCTS‐g‐AT in detection of Hg(II) in aquatic products

AbstractThe MCTS‐g‐AT was developed as a novel magnetic adsorbent with core‐shell structure. Its unique synthesis route endows MCTS‐g‐AT with green, convenient, economical and safe characteristics, and also good selective adsorption of Hg(II). The material was characterized using an appropriate set of spectroscopic and analytical techniques (SEM, EDS, XRD, VSM, FTIR, and TGA). Its adsorption kinetics fits the pseudo‐secondary model well and adsorption isotherm fits the Langmuir equation well, suggesting the mechanism of chemisorption with monolayer adsorption. The results of the thermodynamic parameters indicate spontaneous and endothermic process. Column adsorption experiments showed that the maximum adsorption capacity of Hg(II) was 207.6 mg/g (298 K). Moreover, the Hg(II) adsorbed on composite microspheres was completely eluted by 3 mol/L HNO3 or 4 mol/L HCl. Furthermore, MCTS‐g‐AT adsorption column combined with spectrophotometer can achieve more accurate detection of Hg(II) in aquatic products.

Cr(VI) reduction coupled with Cr(III) adsorption/ precipitation for Cr(VI) removal at near neutral pHs by polyaniline nanowires-coated polypropylene filters

BackgroundLimited work was done about remediation of Cr(VI))-contaminated water at near neutral pHs (6-8), such as drinking water resources. MethodsPolyaniline nanowires-coated polypropylene filter (PANI-PP filter) was fabricated for easy recollection and reuse of spent adsorbents. The physicochemical properties of PANI nanowires were characterized by SEM, FTIR, BET, and XPS. The effect of solution pH, contact time, and Cr(VI) concentration on Cr(VI) reduction and total Cr removal are investigated with batch and column adsorption experiments. FindingsThe PP filter provided micro-sized fiber for PANI deposition, and the deposited PANI nanowires exhibited higher surface area and Cr(VI) removal ability than the PANI powders formed in synthetic solution. At near neutral pHs, Cr(VI) removal by PANI-PP filter was attributed to the Cr(VI) adsorption by the amine groups, Cr(VI) reduction to Cr(III), and subsequent Cr(III) adsorption/precipitation on the PANI nanowires, and the maximum removal capacity of Cr(VI) and total Cr were in the range of 55.7 to 113.8 mg/g PANI. The Cr(VI) reduction was accompanied with the oxidation of amine groups to imine groups of PANI. The electro-chemical regeneration promoted the reduction of imine groups back to amine groups, and after 10 regeneration cycles, around 105% Cr(VI) removal efficiency was still achieved.

Efficient separation and recovery of Re(VII) from Re/U bearing acidic solutions using aminotriazole modified cellulose microsphere adsorbents.

In this work, aminotriazole-modified microcrystalline cellulose microsphere (3-ATAR) containing an abundant nitrogen content as promising adsorbent was prepared via a radiation grafting method for the selective recovery ReO4- in the presence of UO22+ in acidic solution. A series of batch and column adsorption experiments including monocomponent and binary systems were designed for evaluating the adsorption and separation performance of Re(VII) onto 3-ATAR. The 3-ATAR exhibited a good adsorption capacity (max 146.4 mg·g-1) of Re(VII) and a rapid adsorption rate, with equilibrium time of 45 min. In binary solution, the high selectivity coefficients (βRe/M) indicated that 3-ATAR could separate and recover Re(VII) from U(VI) and other metal ions (Cu(II), Cr(III), Ni(II), Zn(II)). In particular, it was found that the adsorption of Re was almost unaffected in U/Re-bearing solutions no matter how much the U(VI) was changed. In the column experiment, when the concentration of U(VI) was 40 times higher than that of Re(VII), 3-ATAR manifested high Re(VII) selectivity over U(VI) from a synthetic uranium ore leachate. This work demonstrated that 3-ATAR could provide an efficient, selectively, sustainable, and industrially feasible way for Re(VII) to be recovered from uranium ore leachate and other prospective sources.Graphical abstract.

Aminated chitosan/cellulose nanocomposite microspheres designed for efficient removal of low-concentration sulfamethoxazole from water

The ppt to ppb sulfamethoxazole (SMX) entering natural water bodies and possibly present in drinking water is not significantly removed and remain persistent and toxic by conventional adsorbents. Aminated chitosan/cellulose nanocomposite microspheres (ACNM) were prepared by in-situ solid phase grafting methods for low concentration of SMX removal. The physical and chemical properties of ACNM were characterized by SEM, FTIR and XRD etc. 10 mg L−1 SMX was used to simulate the low concentration of SMX in the aqueous phase, SMX adsorption on ACNM could reached the equilibrium within 30 min. The adsorption process was better kinetically fitted with the pseudo-second-order kinetic model and Langmuir isothermal model, suggesting that monolayer chemical adsorption was the dominant adsorption process. The removal efficiency of SMX reached 99.18%, and the adsorption capacity was 13.59 mg g−1. The adsorption mechanism was also studied. ACNM retained 96.8% of the initial adsorption capacity after 3 cycles. Column adsorption experiments were studied to determine the best adsorption conditions.

Microwave treated activated carbon from industrial waste lignin for denitrification of surface water

Highly porous adsorbent materials were developed from industrial waste lignin for denitrification of surface and groundwater. The effect of microwave treatment and zinc ion impregnation on denitrification capacities of the material was investigated. The denitrification efficiencies of prepared materials were investigated by performing batch and continuous column adsorption experiments. The effect of different experimental parameters, including initial nitrate ion concentration, solution pH, and contact time, was also investigated. Adsorption kinetic follows the pseudo-second-order kinetic mechanism. Adsorption isotherm follows the monomolecular adsorption and experimental data best fitted into the Langmuir isotherm model. Continuous column denitrification experiments were performed with granulated adsorbent at different experimental conditions to understand its applicability in the household water treatment unit. Thomas model breakthrough time and the nitrate removal efficiency increase with increasing bed depth, whereas it declines with flow rate and nitrate concentration. The economic viability and environmental friendliness were understood by conducting adsorption–desorption experiments with loaded materials. The performance of adsorbent did not alter significantly even after four consecutive adsorption–desorption cycles.

Carboxylated UiO-66 Tailored for U(VI) and Eu(III) Trapping: From Batch Adsorption to Dynamic Column Separation

U(VI) and Eu(III), as representative elements of the hexavalent actinide and trivalent lanthanides (always as a chemical analogue for trivalent actinide), respectively, have attracted more and more attentions due to the widespread use of nuclear energy. Much effort has been focused on developing versatile materials for their uptake from aqueous solution. For the first time, we report here UiO-66 and its mono- (UiO-66-COOH) and di-carboxyl (UiO-66-2COOH) functional derivatives as robust adsorbents for efficient U(VI) and Eu(III) removal. It is found that the introduction of carboxyl groups greatly reduces the surface charge of UiO-66, thus guaranteeing excellent adsorption capacity at low pH. At pH = 3, for example, the adsorption capacity of UiO-66-2COOH for U(VI) and Eu(III) is more than 100 and 60 mg/g, respectively, while almost no adsorption occurs for pristine UiO-66. At pH = 4, both UiO-66-COOH and UiO-66-2COOH show high performance on U(VI) and Eu(III) removal. UiO-66-COOH has adsorption capacities of 80 and 43 mg/g for U(VI) and Eu(III), respectively, while the values for UiO-66-2COOH reach 150 and 80 mg/g, respectively. Also, all these materials achieve adsorption equilibrium within 100 min. More importantly, combining the needs of practical applications and the characteristics of high stability, high porosity, and excellent adsorption performance of UiO-66-2COOH, dynamic adsorption column experiments were successfully conducted; ∼99% U(VI)/Eu(III) can be efficiently adsorbed, and >90% adsorbed U(VI)/Eu(III) can be re-collected with dilute nitric acid solution, even after four adsorption-desorption cycles. The findings of this work demonstrate the application potential of metal-organic framework materials to remove radionuclides from environmental samples or nuclear waste liquids.

Alkaline modification of the acid residue of incinerated sewage sludge ash after phosphorus recovery for heavy metal removal from aqueous solutions

Enriched in phosphorus, sewage sludge ash has been extensively studied and applied as a secondary source for phosphorus recovery. Wet extraction, especially acid washing, is one of the most feasible methods to recover phosphorus from the ash due to its ease of operation, high efficiency and low cost. However, the management of the resultant acid residue was seldom addressed. In this study, special focus was paid to the reuse and recycling of the acid residue by an alkaline activation method. Its adsorption performance towards four different heavy metals in aqueous solutions was evaluated by batch and fixed-bed column adsorption experiments. The obtained material showed a high BET specific area (98.29 m2/g) and a total pore volume (0.114 cm3/g), and effectively removed Cd(II), Cu(II), Pb(II) and Zn(II) from aqueous solutions with the maximum adsorption capacity of around 26.8, 22.2, 53.3 and 13.5 mg/g respectively. It could be loaded in a fixed-bed column to continuously remove heavy metals especially for Pb(II). The proposed method to recycle the acid residue makes the wet extraction methods designing to recover phosphorus from incinerated sewage sludge complete without the generation of waste, which contributes to circular economy and a sustainable future.

Adsorption capacity of nitrate from artificial fertilizers and soil on pyrophyllite

The study at hand presents for the first time the use of pyrophyllite as adsorbent for nitrate removal from soil and artificial fertilizers. A series of column and batch adsorption experiments were conducted to examine the effects of the adsorbent’s various parameters, the contact time, pH of the solution, the initial concentration of nitrate, concentration and adsorbent granulometry. Pyrophyllite fractions of 0.25, 0.50 and 1.00 mm had very similar pH values of aqueous suspensions and were in the weakly basic range. Nitrate adsorption capacity on pyrophyllite expressed by recovery factor values ranges from 93.14 to 99.77%. High recovery factor values from 90.44 to 97.45% for 1, 3, 5 and 8 mL min−1 flow rates were obtained using all pyrophyllite fractions. Nitrate removal was very effective by the contact time of 1 and 2 h, and the recovery factor values were in the range of 90.38–91.47% and 92.15–93.18% for a contact time of 1 h and 2 h, respectively. In addition, elution of nitrate from pyrophyllite was performed using the following solution with different pH values: 1.70 (synthetic gastric juice), 6.40 (rainwater), 7.70 (distilled water), 9.30 and 12.50 (NaOH solution). Elution was very low for all used solutions and was the highest at the pH 9.30. The results show that the use of pyrophyllite for removal of nitrate from artificial fertilizers and soil was an adequate approach because it has a high nitrate adsorption capacity, while the nitrate elution from the pyrophyllite was very low.

A comparative study of immobilizing ammonium molybdophosphate onto cellulose microsphere by radiation post-grafting and hybrid grafting for cesium removal.

Ammonium molybdophosphate (AMP) exhibits high selectivity towards Cs but it cannot be directly applied in column packing, so it is necessary to prepare AMP-based adsorbents into an available form to improve its practicality. This work provided two AMP immobilized cellulose microspheres (MCC@AMP and MCC-g-AMP) as adsorbents for Cs removal by radiation grafting technique. MCC-g-AMP was prepared by radiation graft polymerization of GMA on microcrystalline cellulose microspheres (MCC) followed by reaction with AMP suspension, and MCC@AMP was synthesized by radiation hybrid grafting of AMP and GMA onto MCC through one step. The different structures and morphologies of two adsorbents were characterized by FTIR and SEM. The adsorption properties of two adsorbents against Cs were investigated and compared in batch and column experiments under different conditions. Both adsorbents were better obeyed pseudo-second-order kinetic model and Langmuir model. MCC-g-AMP presented faster adsorption kinetic and more stable structure, whereas MCC@AMP presented more facile synthesis and higher adsorption capacity. MCC@AMP was pH independent in the range of pH 1-12 but MCC-g-AMP was sensitive to pH for Cs removal. The saturated column adsorption capacities of MCC@AMP and MCC-g-AMP were 5.4g-Cs/L-ad and 0.75g-Cs/L-ad in column adsorption experiments at SV 10 h-1. Both adsorbents exhibited very high radiation stability and can maintain an adsorption capacity of >85% even after 1000kGy γ-irradiation. On the basis, two AMP-loaded adsorbents possessed promising application in removal of Cs from actual contaminated groundwater. These findings provided two efficient adsorbents for treatment of Cs in radioactive waste disposal.

Facile synthesis and implications of novel hydrophobic materials: Newer insights of pharmaceuticals removal

The residual escape of pharmaceuticals from wastewater treatment plants (WWTP) is a serious environmental concern due to the adverse effects towards living organisms. Therefore, it is important to devise the newer technologies for safe and efficient elimination of emerging micro-pollutants from effluents of existing water treatment plants. Bentonite is grafted with 3-mercaptopropyletrimethoxy silane by facile one-pot method to obtain dense composite material (MPTS/BENT).The materials are characterized by the FT-IR, XRD, BET and SEM/EDX analytical tools. Various parametric experiments conducted for the removal of tetracycline hydrochloride (TCH) and triclosan (TCS) using MPTS/BENT under batch experimentations. Further, column adsorption experiments have been performed.The incorporation of organosilane with bentonite is confirmed by FT-IR and EDX analyses. BET surface area analysis showed that the surface area of MPTS/BENT is significantly small compared with pristine clay. pH dependent sorption of TCH and TCS is almost unaffected within the pH 3.0 to 7.0. Rapid uptake of TCH and TCS by MPTS/BENT followed PSO kinetics. High percentage removal was achieved at wide concentration range of pollutants. The uptake of TCH and TCS is unaffected increasing the background electrolyte concentrations for 1000 times. Column experiment confirmed the high efficiency of MPTS/BENT towards these pollutants. Moreover, the removal of TCH/or TCS from real water sample at varied pH values showed that the synthesized composite is selective and efficient towards these micro-pollutants. This study showed that the synthesize material, i.e., MPTS/BENT could be efficiently employed for the additional purification of WWTP effluents.

Magnetic hollow buoyant alginate beads achieving rapid remediation of oil contamination on water

Oil spills are a worldwide concern because of their negative impact on the environment. Thus, the development of simple yet effective methods for oil pollution remediation remains a significant global challenge. Of remediation techniques for oil removal, those involving adsorption are superior, but most reported adsorbents sink in water and are, consequently, difficult to collect after adsorption, generating secondary pollution. Thus, we developed magnetic maleic anhydride–alginate graphene oxide hollow beads (GO-MAGB-MA). Here, we report the characterization of GO-MAGB-MA, involving scanning electron microscopy, energy dispersive X-ray spectrometry, Raman spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and vibrating sample magnetometry. The experimental data fit the pseudo-second order kinetic model, having a chi-squared (χ2) ≤ 0.0069, average relative error (ARE) ≤ 0.4094, and coefficient of determination (R2) ≥ 0.9998, and the Freundlich isotherm, having χ2 ≤ 3.33 × 10−4, ARE ≤ 0.2349, and R2 ≥ 0.9966, indicating that removal of oil was the rate-limiting step on heterogenous multilayer system. In comparison with other previous reported adsorbents, the GO-MAGB-MA shows superiority in term of adsorption process which was pH independent, rapid equilibrium adsorption and high adsorption capacity. GO-MAGB-MA also remained buoyant and magneto-responsive during adsorption process made it easy to be-recollected and regenerated while other reported adsorbents tend to sink during adsorption, and difficult to be re-recollected and ended as secondary pollutants. For future application, Combination with other technologies such as skimmer and continuous column adsorption experiment can be conducted for larger-scale oily water remediation.

Enhanced Removal of Heavy Metals from Water by Hydrous Ferric Oxide-Modified Biochar.

Biochar has become an attractive adsorbent for heavy metal removal, but its application potential is very limited because of the relatively low adsorption capacity and poor selectivity. In the present study, we decorated the biochar (BC) by impregnating hydrous ferric oxide (HFO) within the pore of biochar and consequently obtained a new hybrid adsorbent denoted as HFO-BC. The results show HFO-BC exhibited excellent performance to two representative heavy metals, i.e., Cd(II) and Cu(II), with maximal experimental sorption capacities of 29.9 mg/g for Cd(II) and 34.1 mg/g for Cu(II). HFO-BC showed satisfactory anti-interference ability for Cd(II) and Cu(II) removal in the presence of high levels of Ca(II) and Mg(II) owing to the specific inner-sphere complexation between the immobilized HFO and Cd(II) and Cu(II), which was probed by XPS analysis. Cd(II) and Cu(II) removal onto HFO-BC experienced two distinct stages prior to be adsorbed, i.e., migration from solution to the outside surface of adsorbent and pore diffusion and approached equilibrium within 100 min. In the laboratory-scale small column adsorption experiment, HFO-BC can generate ∼129 and 300 BV effluents for Cd(II) and Cu(II), equivalent to 774- and 1854-fold of its own weight, to meet their treatment standards. Moreover, the exhausted HFO-BC can be effectively regenerated using HCl–CaCl2 binary solution with a desorption rate more than 95%. All results validate that impregnating HFO inside the pores of BC is a promising approach to promote the practical applicability of BC for removing heavy metals from the polluted water.

Batch and column studies using doped polymer for elimination of Sodium 4-[4-(dimethylamino) phenyl] diazenyl benzene-1-sulfonate from wastewater

ABSTRACT In the present research Polyaniline (PANI) has been prepared by chemical polymerisation using oxalic acid (OA) as a dopant. Removal of Methyl Orange (MO), (Sodium 4-{[4-(dimethylamino) phenyl] diazenyl} benzene-1-sulphonate), from wastewater, has been carried out using Oxalic acid (OA) doped Polyaniline. Breakthrough curves have been obtained from column adsorption experiments. Maximum dye adsorption was witnessed at pH 3. Four isotherm models were studied for the adsorption data and the subsequent constants have been calculated. The mean adsorption energy estimated from the D-R isotherm model has been determined as 1.5 × 104 J mol−1. Thermodynamic investigations intimated the spontaneity as well as endothermicity, with an entropy change of (79 J mol−1 K−1). Kinetic experiments divulged the adsorption of the dye by a second-order mechanism. The film diffusion mechanism was predominating at all studied temperatures. The percentage saturation for PANI column is 99.98% with the adsorption capacity of adsorbent as 8.36 mg/g. The recovery of dye has been accomplished by 0.1 N NaOH through the exhausted column. Results demonstrated PANI to be an excellent adsorbent for the eradication of the hazardous dye from textile wastewater.

High-efficiency removal of low-concentration Hg(II) from aqueous solution by bentonite nanocomposite: Batch and fixed-bed column adsorption study

ABSTRACT A nanocomposite based on bentonite was synthesized. Its adsorption properties for Hg(II) were evaluated by batch and fixed-bed column adsorption experiments. The results showed that the nanocomposite was an efficient adsorbent for the treatment of wastewater containing low-concentration Hg(II). It removed more than 92% of Hg(II) from aqueous solution with a pH ranged from 4.00 to 12.00. Its adsorption capacity for Hg(II) increased linearly with the increase of mercury concentration. The nanocomposite had excellent reusability. HCl solution can be used to elute Hg(II) ions loaded. The developed Bohart–Adams model can be used for the design of adsorption column.

Phosphorus removal by adsorbent based on poly-aluminum chloride sludge

Phosphorus adsorption tests were carried out using poly-aluminum chloride sludge (PACS), which was collected from a water treatment plant in Nanjing. The amount of phosphorus adsorbed by PACS increased quickly within the first hour and reached equilibrium after about 48 h. The adsorption behavior of PACS for phosphorus is consistent with the Langmuir adsorption isotherm equation (R2 > 0.99) and parallel first-order kinetic equation (R2 > 0.98). With the increase of the PACS concentration, the adsorption capacity of PACS for phosphorus decreased, and the removal rate increased. The results of batch tests showed that the adsorption capacities of PACS for phosphorus ranged from 1.64 to 1.13 mg/g when the pH value varied from 4 to 10. However, the adsorption capacity of PACS was not evidently influenced by temperature. In comparison with the ion exchange resin, the adsorption capacity of PACS was barely inhibited by competitive ions, such as SO42−, NO3−, and Cl−. The PACS surface after adsorption became smooth, and the vibration peaks of Al–O and Al–OH shifted. Both HCl and NaOH have a strong desorption effect on PACS after adsorption saturation, and with higher concentrations of HCl and NaOH, the desorption effect was stronger. Results of column adsorption experiments showed that with lower phosphorus and hydraulic loads, the adsorption column took longer to reach saturation. This indicated that PACS could be used as an efficient material for removal of phosphorus from water. This study provides a new treatment method with PACS.

A calcined clay fixed bed adsorption studies for the removal of heavy metals from aqueous solutions

A natural clay material from southern Tunisia was used as a low cost sorbent in a column-wise removal of metal pollutants. This is fundamentally important for a sustainable wastewater treatment strategy. This work has been performed within the framework of a project aiming to the valorization of natural geomaterials, from Tunisia, in several environmental applications. Column adsorption experiments were carried out for a better production of cleaner effluents and further understanding of the main mechanisms involved in the removal process, through a dynamic methodology, that would allow an industrial scale treatment. A calcined clay sample was used as an adsorbent for the removal of Pb(II), Cr(VI) and Cd(II) from aqueous solution. Lead removal, in presence of copper and zinc, was also studied. The effect of various parameters including bed height (2.0, 4.0 and 6.0 cm), flow rate (3, 5.8 and 9 mL/min) and influent metal ion concentrations (50, 100 and 150 mg/L) were investigated at an influent pH of 6. It was found that the exhaustion time increased with the increase of bed depth, the decrease of flow rate and initial concentration. Bohart -Adams, Thomas, Yoon–Nelson and Advection diffusion models were applied to the experimental data to predict the breakthrough curves for a better understanding of the main adsorption mechanisms. The assessment of the calcined clay performance may further explain the mechanism of metals-sorbent interaction at the water-clay interface. Thomas and Advection diffusion models were in good agreement with the experimental data. Column-wise packing of clays achieved excellent adsorption performances of metal ion in aqueous solution. The obtained results suggested a possible extension to the industrial scale of the fixed bed adsorption systems for cleaner water production, especially in the southern Tunisian districts where uncontrolled effluents discharge needs an immediate application of monitoring programs to for a sustainable improvement of water quality.

Synthesis and Application of Recyclable Core-Shell Structure Microspheres Mcts-G-At in Detection of Hg(Ⅱ) in Aquatic Products

The MCTS-g-AT was developed as a novel magnetic adsorbent with core-shell structure. Its unique synthesis route endows MCTS-g-AT with green, convenient, economical and safe characteristics, and also good selective adsorption of Hg(Ⅱ). The material was characterized using an appropriate set of spectroscopic and analytical techniques (SEM, EDS, XRD, VSM, FTIR and TGA). Its adsorption kinetics fits the pseudo-secondary model well and adsorption isotherm fits the Langmuir equation well, suggesting the main adsorption mechanism of chemisorption with monolayer adsorption. The results of the thermodynamic parameters indicate that the adsorption process is spontaneous and endothermic. Column adsorption experiments showed that the maximum adsorption capacity of Hg(II) was 207.6 mg/g (298 K). Moreover, the Hg(II) adsorbed on composite microspheres was completely eluted by 3 mol/L HNO 3 or 4 mol/L HCl. Furthermore, MCTS-g-AT adsorption column combined with spectrophotometer can achieve more accurate detection of Hg(II) in aquatic products.

Batch and column adsorption of cations, oxyanions and dyes on a magnetite modified cellulose-based membrane

An optimized method is presented to make magnetite (MG) modified cellulose membrane (Cell-MG) from 3-aminopropyltriethoxysilane and diethylenetriaminepentaacetic acid dianhydride functionalized waste cell fibers; (Cell-NH2 and Cell-DTPA), and amino-modified diatomite. Functionalized Cell-NH2, Cell-DTPA fibers, and diatomite were structurally and morphologically characterized using FT-IR, Raman, and FE-SEM analysis. Amino and carboxyl group content was determined via standard volumetric methods. Response surface method was applied to rationalize the number of experiments related to Cell-MG synthesis and heavy metal ions column adsorption experiments. The effects of pH, contact time, temperature, and initial concentration of pollutants on adsorption and kinetics were studied in a batch, while initial concentration and flow rate were studied in a flow system. The calculated capacities of 88.2, 100.7, 95.8 and 78.2 mg g−1 for Ni2+, Pb2+, Cr(VI) and As(V) ions, respectively, were obtained from Langmuir model fitting. Intra-particle diffusion as a rate-limiting step was evaluated from pseudo-second-order and Weber–Morris model fitting. Thermodynamic parameters indicated spontaneous and low endothermic processes. The results from reusability study, wastewater purification and fixed-bed column study proved the high applicability of Cell-MG. Additionally, high removal capacity of four dyes together with density functional theory and molecular interaction fields, help in the establishment of relation between the adsorption performances and contribution of non-specific and specific interactions at adsorbate/adsorbent interface.

Iron and zirconium modified luffa fibre as an effective bioadsorbent to remove arsenic from drinking water

Porous luffa plant fibre (LF) was grafted with Fe and Zr, and the ability of the fabricated adsorbents to remove arsenate (As(V)) from water was investigated in batch and column adsorption experiments. The Langmuir adsorption capacity (mg g−1) at pH 7 of LF was found to be 0.035, which increased to 2.55 and 2.89 after being grafted with Fe (FLF-3) and Zr (ZLF-3), respectively. Grafting with Fe and Zr increased the zeta potential and zero point of charge (ZPC) of LF (from pH 3.9 to 7.4 for Fe grafting and to 7.6 for Zr grafting), due to chemical bonding of the metals, possibly with the hydroxyl and carboxylic groups in LF as indicated in FTIR peaks. Zeta potential and ZPC decreased after As adsorption owing to inner-sphere complexation mechanism of adsorption. The increase of pH from 3 to 10 progressively reduced the adsorbents’ adsorption capacity. Co-existing anions weakened the As(V) removal efficiency in the order, PO43− > SiO32− > CO32− > SO42−. Adsorption kinetics data fitted well to the Weber and Morris model, which revealed initial fast and subsequent slow rates of intra-particle As diffusion into the bigger pores and smaller pores, respectively. Column adsorption data fitted well to the Thomas model with the predicted adsorption capacities in the same order as in the batch adsorption experiment (ZLF-3 > FLF-3 > LF).