Consecutive Sorption-desorption Cycles Research Articles

Selective biosorption and recovery of scandium using the alga Fucus vesiculosus

The goal of this work was to study the viability of the application of biosorption using the brown alga Fucus vesiculosus in the recovery of scandium from red mud. The highest affinity of the biosorbent for scandium and aluminium was at pH 3. Sorption isotherms fitted to the Langmuir model for scandium and aluminium with adsorption capacities as high as 1.04 mmol·g−1 for both metals but with higher affinity for scandium than for aluminium. The performance of the biomass in fixed-bed columns was evaluated in different experimental conditions (flow rate, bed height and inlet metal concentration). Metal desorption was achieved with different inorganic and organic acids. After three consecutive sorption–desorption cycles using 0.1 N citric acid and deionized water during the regeneration step, the brown alga showed a progressive increase in scandium uptake due to the cross-linking citric acid and the alginate chains. The biomass was characterized before and after biosorption using Fourier transforms infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) coupled with an energy dispersive elemental analyser (EDS). The sorption involves different functional groups, such carboxylate and sulphonic groups by chelation and electrostatic interactions.

The influence of chemical composition and preparation procedure on CO2 capture performance of NaNO3 /MgO-based sorbents

MgO based sorbents modified by 5–50 mol.% NaNO3 have been prepared by various methods and investigated in detail. It has been showed that optimal synthesis method is incipient wetness impregnation of MgO precursor with sodium nitrate water solution. The highest sorption capacity of 6.5 mmol CO2 g–1 sorb after 1 hour of sorption from the gas mixture with 50 vol.% CO2 at 320 °C was achieved using the MgO modified by 10 mol.% NaNO3. Sorption capacity for MgO modified by 10 mol.% NaNO3 during 10 consecutive sorption-desorption cycles is approximately 4.5–5.5 mmol CO2 g–1 sorb. The duration of the sorption stage is 30 min, the CO2 content in the feed gas is 50 vol.% and sorption-regeneration temperature is 300–350 °C respectively. It has been showed that increasing the sorption pressure to 10 bar allows reducing sorption temperature from 320 °C to 220–260 °C. The sorption capacity is reached up to 4.0 mmol CO2 g–1 sorb at 25 vol.% CO2 that is twice higher than that at 1 bar. It has been demonstrated that steam and hydrogen treatment before sorption doesn’t lead to a significant change in the sorption properties and phase composition of NaNO3 modified MgO-based sorbent.

Yeast biomass ornamented macro-hierarchical chitin nanofiber aerogel for enhanced adsorption of cadmium(II) ions

There is an urgent need to develop sustainable, renewable, and environment-friendly adsorbents to rectify heavy metals from water. In the current study, a green hybrid aerogel was prepared by immobilizing yeast on chitin nanofibers in the presence of a chitosan interacting substrate. A cryo-freezing technique was employed to construct a 3D honeycomb architecture comprising the hybrid aerogel with excellent reversible compressibility and abundant water transportation pathways for the accelerated diffusion of Cadmium(II) (Cd(II)) solution. This 3D hybrid aerogel structure offered copious binding sites to accelerate the Cd(II) adsorption. Moreover, the addition of yeast biomass amplified the adsorption capacity and reversible wet compression of hybrid aerogel. The monolayer chemisorption mechanism explored by Langmuir and pseudo-second-order kinetic exhibited a maximum adsorption capacity of 127.5 mg/g. The hybrid aerogel demonstrated higher compatibility for Cd(II) ions as compared to the other coexisted ions in wastewater and manifested a better regeneration potential following four consecutive sorption-desorption cycles. Complexation, electrostatic attraction, ion-exchange and pore entrapment were perhaps major mechanisms involved in the removal of Cd(II) revealed by XPS and FT-IR. This study unveiled a novel avenue for efficient green-synthesized hybrid aerogel that may be sustainably used as an excellent purifying agent for Cd(II) removal from wastewater.

Removal of Cr(VI) by ultrafiltration enhanced by a cellulose-based soluble polymer

In this study, polymer-enhanced ultrafiltration (PEUF) was used to remove chromium ions (Cr(VI)) from water using quaternized hydroxyethyl cellulose ethoxylate (QHECE) as the extracting agent. The polymer was structurally and thermally characterized before and after loading, where Fourier transform spectra were used to corroborate the Cr(VI) binding sites. Thermogravimetric analysis showed an increase in the residual mass due to the formation of macromolecular aggregates from the water-soluble polymer (WSP) and Cr(VI). SEM/EDX was used to corroborate the presence of Cr(VI) on the WSP surface. The washing method was used to study Cr(VI) retention as a function of the solution pH, WSP quantity, pressure, Cr(VI) concentration, membrane type and presence of interfering ions (NaCl, Na2SO4 and NaHPO4) at three Cr(VI):interferent molar ratios (1:1, 1:2 and 1:4). In addition, the polymer reusability was studied over six sorption-desorption cycles. Next, the enrichment method was used to determine the maximum retention capacity of the polymer. Finally, PEUF was used to test Cr(VI) removal in simulated industrial electroplating wastewater.By varying different parameters, 92 % retention efficiency was achieved at pH 9.0 using a polymer mass of 50 mg, a pressure of 2.0 bar, an initial Cr(VI) concentration of 30 mg L−1 and a 10-kDa regenerated cellulose membrane. Increasing the Cr(VI):interferent molar ratio was found to decrease the retention efficiency, and significant decrease was obtained for the highest ratio of sulfonate ions to Cr(VI) used. Finally, the maximum retention capacity was determined to be 299.46 mg g−1 using the enrichment method, and it was demonstrated that the polymer could be reused for up to four consecutive sorption-desorption cycles.

In-situ magnetization of porous carbon beads by pyrolysis of waste red mud doped polysulfone beads for efficient oil sorption

This study describes for the first time the preparation of in-situ magnetic porous carbon beads (MPC beads) through simple phase inversion and subsequent pyrolysis of red mud doped polysulfone beads. Red mud, which is the main industrial waste resulted from the aluminium production, contains an important amount of Fe2O3. Characterization studies demonstrated the in-situ carbo-reduction of Fe2O3 species into magnetic Fe3O4 thanks to polysulfone carbon source, involving then the synthesis of MPC beads. Owing to hydrophobic surface and macroporous structure, the MPC beads were evaluated on the sorption of various oils, including gasoline, diesel oil, mineral oil and olive oil from water. The maximum sorption capacity of the MPC beads for examined oils were determined as olive oil (2.018 ± 0.162 g/g)>mineral oil (1.418 ± 0.138 g/g)> diesel oil (1.316 ± 0.062 g/g)>gasoline (1.235 ± 0.028 g/g). Moreover, the MPC beads were regenerable by heat treatment and there was no change in their sorption capacities in the first ten consecutive sorption-desorption cycles. Consequently, the suggested approach on the pyrolysis of waste red mud doped polysulfone beads was successful at preparing in-situ MPC beads, which can be efficiently used for oil spills clean-up from water with easier separation by a magnet.

Synthesis of Poly(methacrylic acid)/Montmorillonite Hydrogel Nanocomposite for Efficient Adsorption of Amoxicillin and Diclofenac from Aqueous Environment: Kinetic, Isotherm, Reusability, and Thermodynamic Investigations.

Herein, a simplistic redox polymerization strategy was utilized for the fabrication of a poly(methacrylic acid)/montmorillonite hydrogel nanocomposite (PMA/nMMT) and probed as a sorbent for sequestration of two pharmaceutical contaminants, viz., amoxicillin (AMX) and diclofenac (DF), from wastewater. The synthesized hydrogel nanocomposite was characterized by the Fourier transform infrared, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy–energy dispersive X-ray spectroscopy, and transmission electron microscopy techniques to analyze structural characteristics and sorption interactions. The efficacy of PMA/nMMT was thoroughly investigated for the sequestration of AMX and DF from the aquatic phase with a variation in operative variables like agitation time, sorbent dosage, pH, and initial sorbate concentration. The reaction kinetics was essentially consistent with the pseudo-second-order model with rate dominated by the intraparticle diffusion model as well as the film diffusion mechanism. The Freundlich isotherm appropriated the equilibrium data over the entire range of concentration. Thermodynamic investigation explored the spontaneous and endothermic nature of the process. The most possible mechanism has been explained, which includes electrostatic interaction, hydrogen bonding, cationic exchange, and partition mechanism. Economic feasibility, better sorption capacity (152.65 for AMX and 152.86 mg/g for DF), and efficient regeneration and reusability even after four consecutive sorption–desorption cycles ascertained PMA/nMMT as a potential sorbent for AMX and DF uptake from the aqueous phase.

Recovery of Ammonium by Powder Synthetic Zeolites from Wastewater Effluents: Optimization of the Regeneration Step

Nitrogen recovery and valorization is gaining interest due to the current need for nitrogen removal, so it is of great interest that ammonium-selective sorbents be evaluated. In this study, a zeolitic material synthesized from coal fly ash (Ze–Na) in sodium form as well as its modification to potassium form (Ze–K) were evaluated as sorbent materials for the recovery of ammonium from wastewater effluents. The sorption performance was assessed through three consecutive sorption-desorption cycles reporting opposite behavior in terms of ammonium sorption capacity. Decreasing in the case of Ze–Na and to slightly increase for Ze–K due to alkaline activation of zeolite surface. The maximum sorption capacities obtained were 109 ± 4 mg NH4/g and 33 ± 1 mg NH4/g for Ze–Na and Ze–K, respectively. It is important to point out that in the case of Ze–Na, the maximum sorbent capacity was obtained during the first sorption cycle whereas in the case of Ze–K, it was obtained during the last working cycle due to the alkaline regeneration. Kinetic studies showed that after every regeneration step, the sorption kinetics turn faster as alkaline desorption increased the zeolite-specific surface, thus increasing the size of porous and enhancing the diffusion through the particle. Results obtained indicate that sorption capacity decreased significantly after every working cycle using Ze–Na whereas Ze–K followed the opposite behavior despite its initial lower sorption capacity.

Biochar for volatile organic compound (VOC) removal: Sorption performance and governing mechanisms

Sorption is one of the most efficient and low cost strategies for volatile organic compound (VOC) removal, but VOC sorption by biochar has seen limited research. In this work, gas phase sorption experiments were conducted to determine the sorption potential and mechanisms of VOCs onto biochar. A total of 15 biochars produced from 5 common feedstocks at 300, 450, and 600°C were evaluated as sorbents. Three common VOCs (acetone, cyclohexane, and toluene) were chosen as sorbates. The results showed that all the tested biochars had VOC sorption capacity in the range of 5.58–91.2mgg−1. The sorption capacities were mainly influenced by both the surface area of biochar and its noncarbonized organic matter content. The vapor sorption process was exothermic, and the removal of VOCs by the biochars decreased with increasing feedstock temperature. Both the physical adsorption and partition mechanisms played important roles in controlling the VOC removal by the biochars. Biochar maintained its VOC removal ability after five consecutive sorption-desorption cycles, which indicated good reusability. Findings of this work suggest that biochar is a promising alternative sorbent for gaseous VOC removal.

Continuous cadmium removal from aqueous solutions by seaweed in a packed-bed column under consecutive sorption-desorption cycles

Packed-bed column process efficiency for cadmium adsorption from aqueous solution was investigated under different bed heights (2.6 to 7.5 cm) and feed flow rates (15 to 30 ml min−1). The column was filled with brown seaweed, Sargassum angustifolium. Three simplified models, including Bed Depth Service Time, Thomas, and Yoon-Nelson were employed for describing the experimental breakthrough curves as well as achieving design parameters. Bed lifetime was also evaluated in several consecutive sorption-desorption cycles. Cadmium concentration of 0.005mg l−1, as a standard limit for potable water, was considered as the breakthrough concentration. The maximum column performance was achieved 81% at 7.5 cm bed length and flow rate of 15 ml min−1. Indeed, increasing the bed height increased the sorption performance and service time, while increasing the feed flow rate had a negative effect. Maximum sorption capacity value remained almost constant by the bed height changes; however, increase in the feed flow rate slightly decreased it. The modeling results revealed that the Yoon-Nelson model was more accurate than Thomas for describing the experimental breakthrough data, especially at low flow rates. Column service time predictions were surprisingly achieved using the Bed Depth Service Time model even at extrapolations. 20% reduction in column adsorption efficiency was observed at the end of four consecutive sorption-desorption cycles; however, desorption efficiencies were achieved more than 99% in each cycle.

Removal of ionizable aromatic pollutants from contaminated water using nano γ-Fe2O3 based magnetic cationic hydrogel: Sorptive performance, magnetic separation and reusability

Acid dyes found in textile industrial effluents are hazardous aromatic pollutants which ionize in aqueous environments. Owing to their non-biodegradability, conventional wastewater treatment processes are not able to remove them and sorptive treatment systems can alternatively be employed. In this study, a nano γ-Fe2O3 based magnetic cationic hydrogel, synthesized through a facile method, was applied for the removal of two acid dyes (Acid Red 27 and Acid Orange 52). The sorption performance (e.g., capacity and kinetics) and solution matrix effects (e.g., pH and competing anions) were investigated. Furthermore, different regeneration conditions (e.g., composition, strength and amount) were tested to develop a suitable regeneration strategy, based on which, reusability of the material was investigated for 30 consecutive sorption–desorption cycles. The material exhibited a rapid sorption rate (99% dye removal within 5min) and sorption isotherm data agreed well with the Langmuir model with an estimated maximum capacity of 833mg/g and 1430mg/g for Acid Red 27 and Acid Orange 52, respectively. The high sorptive performance persisted not only over a wide pH range but also over 30 consecutive rounds of sorption–desorption. Moreover, the impregnated γ-Fe2O3 nanoparticles rendered the hydrogel superparamagnetic allowing its convenient magnetic separation.

Adsorption of rare earths (III) by calcium alginate-poly glutamic acid hybrid gels

BACKGROUND Adsorption is believed to be an effective and green technology for the removal and recovery of rare earths (III) from dilute solution. RESULTS A novel hybrid gel, abbreviated as ALG-PGA, has been prepared through crosslinking calcium alginate (ALG) and γ-poly glutamic acid (PGA), and its adsorption behavior towards whole rare earths (III) has been examined. Taking Nd(III) as a representative element, the adsorption capacity, kinetics, reusability, selectivity and mechanism have been investigated. Cation exchange is proposed as a possible adsorption mechanism. Doping PGA molecules into calcium alginate beads can significantly enhance the adsorption capacity and the selectivity of rare earths from non-rare earths. The maximum adsorption capacity obtained for Nd(III) was 1.65 mmol g−1. Reutilization of ALG-PGA gel was confirmed for up to eight consecutive sorption–desorption cycles with no damage to the gel. CONCLUSION The prepared biosorbent, ALG-PGA, was biocompatible and cost effective with a good adsorption ability for Nd(III), and provides a new approach to the recovery of rare earths (III) from rare earths-containing wastewater. © 2013 Society of Chemical Industry

Sorption of uranium(VI) using oxime-grafted ordered mesoporous carbon CMK-5

A new sorbent for uranium(VI) has been developed by functionalizing ordered mesoporous carbon CMK-5 with 4-acetophenone oxime via thermally initiated diazotization. The sorption of U(VI) ions onto the functionalized CMK-5 (Oxime-CMK-5) was investigated as a function of sorbent dosage, pH value, contact time, ionic strength and temperature using batch sorption techniques. The results showed that U(VI) sorption onto Oxime-CMK-5 was strongly dependent on pH, but to a lesser extent, on ionic strength. Kinetic studies revealed that the sorption process achieved equilibrium within 30 min and followed a pseudo-first-order rate equation. The isothermal data correlated with the Langmuir model better than the Freundlich model. Thermodynamic data indicated the spontaneous and endothermic nature of the process. Under current experimental conditions, a maximum U(VI) sorption capacity was found to be 65.18 mg/g. Quantitative recovery of uranium was achieved by desorbing the U(VI)-loaded Oxime-CMK-5 with 1.0 mol/L HCl and no significant decrease in U(VI) sorption capability of Oxime-CMK-5 was observed after five consecutive sorption–desorption cycles. The sorption study performed in a simulated nuclear industry effluent demonstrated that the new sorbent showed a desirable selectivity for U(VI) ions over a range of competing metal ions.

Preparation and adsorption properties of chelating resins containing 3-aminopyridine and hydrophilic spacer arm for Hg(II)

Two novel chelating resins, denoted as PS-DEG-3-AP and PS-TEG-3-AP, were obtained by inserting spacer ethylene oxide and ethylene sulfide, respectively, with 3-aminopyridine (3-AP) into polystyrene- co-divinylbenzene. Fourier transform-infrared spectra (FTIR) and elemental analysis were employed to characterize their structures. The adsorption properties of the resins for Hg(II), Ag(I), Fe(III), Pb(II), Co(II), Cu(II), Ni(II), Cd(II) and Zn(II) had been studied, and the results revealed that the resins had higher adsorption capacities and adsorption selectivity for Hg(II). The adsorption kinetics and adsorption isotherms of the resins for Hg(II) were also investigated. The adsorption data of Hg(II) on the resins were fitted well by the pseudo second-order kinetics. Langmuir and Freundlich models were used to describe Hg(II) adsorption isotherms on both resins. The adsorption mechanisms of PS-DEG-3-AP and PS-TEG-3-AP for Hg(II) were confirmed by X-ray photoelectron spectroscopy (XPS). Furthermore, five consecutive sorption–desorption cycles demonstrated that the resins were suitable for repeated use without considerable change in adsorption capacity.

Remoção de níquel(II) de soluções aquosas pela biomassa <em>Sargassum filipendula</em> em múltiplos ciclos de sorção-dessorção

The behavior of seaweed Sargassum filipendula during a removal of nickel from a 50 mg/L aqueous solution at pH 3.5 in fixed-bed columns operating in adsorption/desorption cycles has been studied. Two elution systems were tested; the first one operating with the direct passage of eluant and the second one with the solution recycle.Then, ten consecutive sorption-desorption cycles were investigated in two packed-bed columns, the first column was regenerated with H2SO4 (0.1 M) and the second one with MgSO4 / H2SO4 (3.5% in pH 3) in eluant recycle system. The sorption and desorption stages were carried out for about 30h and 2 h, respectively, representing 20 days of a continuous use of the biomass. A high quantity of recovered nickel was observed in the elution stages (approximately 97%). After 10 cycles, it was verified that the Sargassum filipendula biomass continued accomplishing elevated values of nickel removal from the solution, showing to be an efficient alternative treatment of wastewaters containing metals. The biomass is easily found and the regeneration presented low cost besides having facilitated the treatment process dispensing successive biomass changes.

Equilibrium, thermodynamic and kinetic studies on biosorption of Pb(II) and Cd(II) from aqueous solution by macrofungus ( Lactarius scrobiculatus) biomass

The equilibrium, thermodynamics and kinetics of the biosorption of Pb(II) and Cd(II) onto ( Lactarius scrobiculatus) macrofungus from aqueous solution were investigated at different experimental conditions. Optimum experimental parameters were determined to be pH 5.5, contact time 60 min, biomass concentration 4 g/L of solution, and temperature 20 °C. The maximum biosorption capacity of L. scrobiculatus was found to be 56.2 mg/g for Pb(II) and to be 53.1 mg/g for Cd(II). The mean free energy values evaluated by using the Dubinin–Radushkevich (D–R) model indicated that the biosorption of the metal ions onto L. scrobiculatus biomass was taken place by chemical ion-exchange. The kinetic studies indicated that the biosorption process of the metal ions followed well pseudo-second order model. The calculated thermodynamic parameters (Δ G°, Δ H° and Δ S°) showed that the biosorption of Pb(II) and Cd(II) ions onto L. scrobiculatus biomass was feasible, spontaneous and exothermic in nature. The recovery of the metal ions from L. scrobiculatus biomass was found as higher than 95% using 1 M HCl and 1 M HNO 3. Furthermore, the reusability of the biosorbent was determined after six consecutive sorption-desorption cycles.

Copper biosorption in a column of pretreated Aspergillus niger biomass

Abstract In this study, biosorption of Cu(II) was investigated in a column of pretreated Aspergillus niger biomass. The breakthrough was measured as a function of influent flow rate and bed height for a feed solution at 10 mg/l metal ion concentration. Biosorption was evaluated in terms of the equilibrium capacity of the column and the amount of metal loading on the A. niger surface. It has been observed that pretreatment of the biomass enhanced the activity of the surface reactive groups and hence the uptake. The breakthrough data obtained was described by bed depth service time (BDST) and Thomas models. The amount of copper adsorbed per gram of pretreated A. niger was 13.4 ± 0.60 mg/g. The sorbed copper was eluted from the column using 0.1N HCl in five consecutive sorption–desorption cycles. For the same initial metal ion concentration, a packed column reactor shows more uptake of Cu(II) in comparison to a batch reactor.

Biosorption of copper by marine algae Gelidium and algal composite material in a packed bed column

Marine algae Gelidium and algal composite material were investigated for the continuous removal of Cu(II) from aqueous solution in a packed bed column. The biosorption behaviour was studied during one sorption–desorption cycle of Cu(II) in the flow through column fed with 50 and 25 mg l −1 of Cu(II) in aqueous solution, at pH 5.3, leading to a maximum uptake capacity of ≈13 and 3 mg g −1, respectively, for algae Gelidium and composite material. The breakthrough time decreases as the inlet copper concentration increases, for the same flow rate. The pH of the effluent decreases over the breakthrough time of copper ions, which indicates that ion exchange is one of the mechanisms involved in the biosorption process. Temperature has little influence on the metal uptake capacity and the increase of the ionic strength reduces the sorption capacity, decreasing the breakthrough time. Desorption using 0.1 M HNO 3 solution was 100% effective. After two consecutive sorption–desorption cycles no changes in the uptake capacity of the composite material were observed. A mass transfer model including film and intraparticle resistances, and the equilibrium relationship, for adsorption and desorption, was successfully applied for the simulation of the biosorption column performance.

Continuous-flow metal biosorption in a regenerable Sargassum column

Metal biosorption behavior of raw seaweed S. filipendula in ten consecutive sorption–desorption cycles has been investigated in a packed-bed flow-through column during a continuous removal of copper from a 35 mg/L aqueous solution at pH 5. The elutant used was a 1% (w/v) CaCl 2/HCl-solution at pH 3. The sorption and desorption was carried out for an average of 85 and 15 h, respectively, representing more than 41 days of continuous use of the biosorbent. The weight loss of biomass after this time was 21.6%. The Cu-biosorption capacity of the biomass, based on the initial dry weight, remained relatively constant at approximately 38 mg Cu/g. Loss of sorption performance was indicated by a shortening breakthrough time and a broadening mass-transfer zone. The column service time, considered up to 1 mg Cu/L in the effluent, decreased continuously from 25.4 h for the first to 12.7 h for the last cycle. The critical bed length, representing the mass-transfer zone, increased almost linearly from 28 to 34 cm. “Life-factors” for S. filipendula were found to be 0.0008 h −1 for the breakthrough time and 0.008 cm/h for the critical bed length, using an exponential decay and linear fitting functions, respectively. Regeneration with CaCl 2/HCl at pH 3 provided elution efficiencies up to 100%. Maximum concentration factors were determined to be in the range 16–44, a decreasing tendency was observed with an increasing exposure time.

Biosorption of Cr, Cu and Al bySargassum biomass

The biosorption and desorption of Cr, Cu and Al were carried out using brown marine algaeSargassum fluitans biomass, known as the good biosorbent of heavy metals. The content of alginate bound to light metals could be changed by physical and chemical pretreatment. The maximum uptake of Cr, Cu and Al was independent of the alginate content. The maximum uptake of Al was two times(mole basis) than those of Cu and Cr. The aluminum-alginate complex was found in the sorption solution of raw and protonated biomass. Most of Cu, Al and light metals sorbed in the biomass were eluted at pH 1.1. However, only 5 to 10% of Cr sorbed was eluted at pH 1.1. The stoichometric ion exchange between Cu and Ca ion was observed on Cu biosorption with Ca-loaded biomass. A part of Cr ion was bound to biomass as Cr(OH)2 + or Cr(OH)2+. Al was also bound to biomass as multi-valence ion and interfered with the desorbed Ca ion. The behavior of rawS. fluitans in ten consecutive sorption-desorption cycles has been investigated in a packed bed flow-through-column during a continuous removal of copper from a 35 mg/L aqueous solution at pH 5. The eluant used was a 1%(w/v) CaCl/HCl solution at pH3.