Potential Sorbent Research Articles

Rapid and solvent-free synthesis of pH-responsive graft-copolymers based on wheat starch and their properties as potential ammonium sorbents

A rapid and cost-effective reactive extrusion (REx) method was employed in this study as an alternative technique for the graft-copolymerization of non-food grade native wheat starch with acrylamide, and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) monomers, with a total starch/monomer ratio of 3:1, using twin-screw extrusion technology. The influence of AMPS content ratio on the REx process was monitored using specific mechanical energy, die pressure and torque values recorded during the extrusion. The as-prepared starch-copolymers were characterized using ATR-FTIR, NMR, TG-DSC, and elemental analysis. An average grafting efficiency and monomer conversion of ~61 and ~86%, respectively, was achieved within 5 min of extrusion at a high starch concentration (0.75:1 w/w starch-water). The copolymer with starch/acrylamide/AMPS weight ratio of 75:20:4 showed the highest swelling capacity in water, while behaving similarly to polyelectrolyte networks in the presence of free ions in both NaCl and NH4Cl solutions. A steady NH4+ adsorption capacity was also recorded for these starch-copolymers within the pH range of ~5.5–8.5, which exceeded those of the natural sorbents. These findings indicate the suitability of the starch-copolymers as potential precursors of effective sorbents, thus confirming the feasibility of using REx to produce pH-responsive hybrid copolymers based on wheat starch at low-cost.

Recommendations for Ensuring Environmental Safety of Ecosystem Restoration After Fire

Purpose. To find ways to improve the soil properties of forest ecosystems after the action of the pyrogen- ic factor: to propose technological measures to restore the quality and improve the soil properties of the ecosystem; to prove the effectiveness of using clay in soil cleaning as a sorbent. Methods. The introduction of clay as a potential sorbent for cleaning fertile soils from trace metals is proposed. The mineral composition of the clay was determined by X-ray phase analysis. Clay materials can be successfully used in adsorption cleaning technologies. The method of phytoremediation with the help of dandelion to concentrate trace metal was used also. The concentration of trace metal was determined by atomic adsorption analysis. Results. The task of the experimental study was to substantiate the possibility of using cheap natural clay raw materials without its prior activation to remove trace metals from the soil solution. In the case of post-pyrogenic relaxation of ecosystems under conditions of man-caused load, the soil in the restored area may be contaminated with VM and other hazardous substances. The clay of the Kharkiv region was chosen for the experiment. The experiment proved the effectiveness of the use of clay in soil purification as a sorbent, and phytoremediation of dandelion in relation to heavy metals. Thus, both technical and biological methods of VM sorption to prepare the soil for planting can be recommended for the restoration of the forest ecosystem after a fire. The proposed technological measures to restore the quality and soil properties of the ecosystem include the implementation of design and survey work, including field research; implementation of the state ecological research (monitoring); cleaning the affected area from damaged trees; reclamation of soil fertility of regenerative territories, provided by design of restoration, depending on characteristic features of damages of sites and the subsequent application of regenerative territories. Conclusions. At postpyrogenic relaxation of ecosystems, in the conditions of technogenic loading, the efficiency of using clay in soil cleaning as a sorbent and phytoremediation with dandelion in relation to heavy metals has been proved.

The performance of emerging materials derived from waste organism blood and saponified modified orange peel for immobilization of available Cd in soil.

Waste organism blood (WOB) and orange peel are emerging stabilization materials obtained as by-products from agricultural processes, which are quite suitable for heavy metal immobilization in soil. In this work, waste organism blood and chemically modified orange peel (SOP) were investigated as potential sorbents for immobilization of available Cd in soil. Application of 5% WOB and SOP effectively immobilized cadmium (Cd) with an associated regulation of soil pH, among which the pH of acidic soil increased most significantly. While the application of 3% SOP alone stabilized almost the same amount of available Cd compared to WOB, it caused the highest stabilization rate of 58.85% when applied at 5%. By contrast, SOP combined with WOB (the mass ratio of the material is 1 : 1) at a 5% addition rate stabilized the available Cd in soils remarkably, with a stabilization rate of 57.74%. This study revealed that the soil particles after stabilization have a more compact and flaky structure, and the SOP and WOB had a particular pore structure, which was helpful for the adsorption of available Cd in soil. This study put forward new insights into the potential effects of Cd immobilization in contaminated soil by newly emerging stabilization biomass materials (WOB and SOP).

Aqueous Lead Removal under Optimized Conditions Using Phosphoric Acid Activated Coconut Coir Activated Carbon

The global burden of heavy metal environmental pollution remains one of the most challenging issues to be addressed urgently. Lead (Pb) has been well recognized as a toxic environmental pollutant. The main objective of this study was to examine the adsorption efficiency of phosphoric activated coconut coir activated carbon for lead (II) removal from an aqueous solution. Synthesized activated carbon was characterized before and after the adsorption of Pb(II) by powder X-Ray diffraction, Fourier transforms infrared spectroscopy and scanning electron microscopy coupled with energy dispersive X-Ray. Furthermore, the removal efficiency of Pb(II) of synthesized activated carbon was tested with different concentrations of Pb(II) solutions, pH levels, adsorbent dosages, and contact time. Atomic absorption spectroscopy was used to analyze the Pb(II) concentrations in water samples. The maximum Pb(II) removal percentage of 100% was obtained with 50 mL of 5 mg/L Pd(II) ion solution and 0.20 g of the synthesized activated carbon. Adsorption data were well fitted with the Freundlich adsorption isotherm model, and adsorption kinetics were fitted with the pseudo-second-order kinetic model with R2 of 0.99. These results conclude that the synthesized activated carbon can be used as a potential sorbent for the removal of lead from wastewaters.

Alginate modified graphitic carbon nitride composite hydrogels for efficient removal of Pb(II), Ni(II) and Cu(II) from water

The removal of heavy metal ions is of great significance to the friendly development of the environment. Herein, alginate modified graphitic carbon nitride composite hydrogels (g-C3N4/SA) were successfully synthesized through a facile cross-linking polymerization method. This novel composite hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS). The effects of different conditions were examined such as pH, initial concentration and contact time. It demonstrated that this integration process significantly improved the adsorption capacity of each component to targeted metal ions and solved the recycling and separation problem of g-C3N4, which is powdery sorbent and hard to recycle after adsorption. The calculated maximum adsorption capacity of Pb(II), Ni(II) and Cu(II) were 383.4, 306.3 and 168.2 mg g−1, respectively. Adsorption isotherms studies showed that the equilibrium adsorption data fitted well to the Langmuir model and the adsorption kinetic data described well with the pseudo-second-order model according to kinetics studies. More significantly, g-C3N4/SA showed excellent regeneration ability and repeatedly utilized at least five cycles without obvious adsorption capacity loss. As-fabricated g-C3N4/SA can be considered as a potential sorbent for highly effective adsorption of Pb(II), Ni(II) and Cu(II) ions from contaminated water.

Zn-substituted iron oxide nanoparticles from thermal decomposition and their thermally treated derivatives for magnetic solid-phase extraction

Controlled thermal decomposition of zinc and iron acetylacetonates in the presence of oleic acid and oleylamine provided surfactant-capped magnetic nanoparticles with narrow size distribution and the mean diameter of ≈15 nm. The combined study by XRD, XRF and Mössbauer spectroscopy revealed three important features of the as-prepared nanoparticles. First, the actual ratio of Zn:Fe was considerably lower in the product compared to the initial ratio of metal precursors (0.14 vs. 0.50). Second, a pure stoichiometric Zn-doped magnetite system, specifically of the composition Zn0.37Fe2.63O4, with no signatures of oxidation to maghemite was formed. Third, Zn2+ ions were distributed at both tetrahedral and octahedral sites, and the observed preference for the tetrahedral site was only twice as high as for theoctahedral site. Furthermore, carbon-coated nanoparticles were achieved by pyrolysis of the surfactants at 500 °C, providing a potential sorbent of organic pollutants with room-temperature magnetization as high as 79.1 emu g−1 and very low carbon content of 5 wt%. The thermal treatment, albeit intended only for the carbonization of surfactants, did alter also the non-equilibrium cation distribution toward the equilibrium one by the relocation of a considerable fraction of the octahedrally coordinated Zn2+ to the tetrahedral sites. Preliminary experiments with magnetic solid-phase extraction of β-estradiol from aqueous solutions evidenced applicability and reusability of the carbon-coated product in the separation of steroid pollutants.

Sol-gel derived, Na/K-doped Li4SiO4-based CO2 sorbents with fast kinetics at high temperature

Li4SiO4 is considered as one of the most potential high-temperature sorbent materials for CO2 capture from the flue gas of fossil fuel-fired power plants. However, it usually suffers from slow kinetics at low CO2 concentrations. In this work, a series of Na- and K-doped Li4SiO4-based sorbents with Na/Si (or K/Si) atomic ratios of 0.05, 0.1 and 0.2 were prepared by a citrate sol-gel method. The prepared materials were characterized by various techniques, which revealed the presence of Li3NaSiO4 (for Na-doped sorbents) and LiKCO3 (for K-doped sorbents) on the surface of Li4SiO4 particles. All Na- and K-doped Li4SiO4 showed greatly enhanced CO2 sorption rates and capacities in 15% CO2 as compared to the heteroatom-free Li4SiO4, and in particular, the Na-doped sorbents had the fastest rates. The improved performance of K-doped Li4SiO4 resulted from the formation of eutectic Li2CO3-K2CO3 molten carbonates during CO2 sorption, while for Na-doped Li4SiO4, both the carbonation of Li3NaSiO4 and the presence of eutectic Li2CO3-Na2CO3 molten salts contributed to the improvement. In addition, both Na- and K-doped Li4SiO4 exhibited incomplete regeneration during cyclic operation, but the latter had better stability. In this context, we deliberately prepared a Na,K-codoped Li4SiO4-based sorbent with a Na:K:Si atomic ratio of 0.1:0.1:1, which showed fast kinetics and good cyclic stability. During 30 consecutive sorption-regeneration cycles (10 min of sorption in 15% CO2 at 650 °C, 5 min of regeneration in pure N2 at 750 °C), the Na,K-codoped Li4SiO4 presented a stable CO2 capture capacity of 0.22 gCO2/gsorbent after the first 10 cycles.

Characterization of raw and chemically activated natural zeolite as a potential sorbent for heavy metal ions from waste water

In this study, raw and chemically activated natural zeolite from Zlatokop deposit (Serbia) were investigated by FTIR, XRD, SEM-EDX, TGA and BET in order to define their properties as further potential sorption materials. Obtained results indicate porous (meso-pore range) and defined crystal alumino-silicate structure of these materials, with Na+, K+, such as Ca2+ and Mg2+ as dominating exchangeable cations. Content of clinoptilolite (ca. 90%) indicates the high quality of the zeolite samples. Preliminary sorption analyses of these materials toward copper(II) ion from aqueous solution showed good removal efficiency for base activated zeolite (zVBB) compared to raw natural (zVBN) and acid activated (zVBA) zeolite. Since these were preliminary sorption tests, the investigated zeolites will be further examined under different experimental conditions.

The Synthesis and Characterizations of Porous Thioamide-Sulfonated-Modified Poly(acrylonitrile-co-divinylbenzene-80) as a Potential Sorbent to Capture Polar Analytes

Pharmaceuticals contain biologically active components that can pollute watercourses as a result of excretion from individuals and the uncontrolled release of residues from chemical plants. Pharmaceutical residues can persist at low concentrations in the environment, and thus may be potentially harmful to aquatic animals and humans. The control and monitoring of such residues are therefore of prime interest by, for example, solid-phase extraction using solid sorbents to purify and preconcentrate the residues prior to their chemical analysis. In the present work, poly(acrylonitrile-co-divinylbenzene-80) (poly(AN-co-DVB-80)) sorbents were synthesised by varying the comonomer feed ratios under precipitation polymerisation conditions to deliver a family of porous polymer microspheres. Acrylonitrile confers polar character onto the sorbents, and the acrylonitrile-derived nitrile groups can be chemically transformed via polymer-analogous reactions into thioamide and sulphonyl functional groups which make the sorbents even more suitable for the capture of polar analytes, including pharmaceuticals. In the present study, the Fourier transform infrared (FTIR) spectroscopy results confirmed the chemical modification of poly(AN-co-DVB-80) (P33) to form thioamide-modified poly(AN-co-DVB-80) (TP33) and sulphonation thioamide-HSO3-modified poly(AN-co-DVB-80) (TP33-HSO3) due to the presence of strong peaks at 1050 cm-1 and 1154.47 cm-1 that were assigned to the stretching vibrations of C=S group and SO3H group in TP33 and TP33-HSO3, respectively. The Bruneaur-Emmett-Teller (BET) data demonstrated that the specific surface area of P33 had decreased significantly from 565.0 m2g-1 (P33) to 330.0 m2g-1 (TP33) and 5.9 m2g-1 (TP33-HSO3) after the chemical modifications were carried out with thiourea and sulphuric acid, respectively. The scanning electron microscopy (SEM) analysis proved that the morphologies structure of the copolymers was retained after chemical modification and sulphonation. The TP33 had 4.3% of sulphur content due to the chemical modification of the P33 with thiourea, while the amount of sulphur in TP33-HSO3 was the highest (6.5%) due to the sulphonation with sulphuric acid. The performance of the porous thioamide-sulphonated (TP33-HSO3) sorbents was demonstrated via the dispersion-solid phase extraction of mefenamic acid (MA), salicylic acid (SA), and diclofenac (DCF) from aqueous medium. It was found that the highly functionalised TP33-HSO3 has better extraction compared to the TP33 despite its low specific surface area. Meanwhile, the extraction of pharmaceuticals by using TP33 was better compared to the extraction by using P33, although the specific surface area (SSA) of TP33 is 330.0 m2g-1 and SSA of P33 is 565.0 m2g1. This finding showed that in addition to the role of SSA that influenced the extraction process; the presence of active functionalised groups also contributed to the extraction efficiency of the sorbents to extract polar pharmaceuticals. It was found that the maximum extraction for TP33 for MA, SA and DCF were 93.88 mg.g1 (78.23%), 80.07 mg.g-1 (66.72%) and 70.70 mg.g-1 (58.91%), respectively, while maximum extraction for TP33-HSO3 were 96.88 mg.g-1 (80.73%), 97.15 mg.g-1 (80.96%) and 69.51 mg.g-1 (57.93%), respectively.

Modeling of Si-B-N Sheets and Derivatives as a Potential Sorbent Material for the Adsorption of Li+ Ion and CO2 Gas Molecule.

In the present exploration, a few Si–B–N derivatives are derived to adsorb Li ions and CO2 gas molecules for the potential application of metal–air batteries. The newly derived structure’s bond lengths are as follows: Si=Si, 2.2 Å; Si–B, 1.9 Å; Si–N, 1.7 Å; and B–N, 1.4 Å, consistent with the experimental results of relevant structures. The stability of the newly derived structures is examined by the atom-centered density propagation study by varying the temperature from 270 to 400 K, and no structural variations are observed throughout the dynamics. Li adsorption on the Si4B2 ring has the maximum binding energy of −3.9 eV, and the result is consistent with the previous results. The rings with the 2:1 silicon–boron ratio provide strong adsorption for Li atoms. The calculated maximum electromotive force of the newly derived sheets is 0.56 V with the maximum theoretical density of 783 Wh/kg. Similarly, the maximum adsorption of CO2 on the sheet is −0.106 eV, which is considerably higher than that on graphene and its derivatives. CO2 adsorption has been carried out in the presence of water molecules to investigate the change in CO2 adsorption with the moisture (water) content, and the results show no significant change in the adsorption of CO2 with moisture. However, water has a strong interaction with the maximum interaction energy of −0.72 eV. Further, to explore the potential ability of the sheets, each sheet’s edges are examined as hydrogen storage expedient and the surface as an artificial photosynthesis platform. The Si4B2 ring is more favorable for the adsorption of H atom with the chemisorption of −7.138 eV. Similarly, all of the major UV-absorption spectral peaks fall between 450 and 800 nm, which shows that the sheet can be used as an artificial photosynthesis platform.

Organo-Modified Vermiculite: Preparation, Characterization, and Sorption of Arsenic Compounds

Among the various technologies tested for removing the anionic species resulting from arsenic contamination, sorption methods have received unflagging interest. Being potential sorbent materials, clay minerals modified by cationic surfactants are often examined for this purpose. Among the clay minerals tested, information regarding sorption properties of expanded vermiculite modified with surfactants is scarce. Therefore, the present study aims to prepare organo-vermiculites modified with hexadecyltrimethylammonium (HDTMA) and benzyldimethylhexadecylammonium (HDBA) at surfactant concentrations of 0.5, 1.0, and 2.0 cation exchange capacity. Modified sorbents were identified and characterized using the analytical methods that can determine phase composition and textural properties of the samples. The sorption of As(III) and As(V) as a function of initial pH value, initial concentration of As(III, V), and initial dosage of sorbent was investigated. The results show that HDTMA and HDBA affect the properties of raw vermiculite. For instance, increase in the concentration of surfactants is often accompanied by a change in interlayer space or textural properties of vermiculite. It was observed that tested organo-minerals adsorbed As(V) to a greater extent compared to As(III). Various analytical studies were carried out and the results revealed the successful synthesis of organo-vermiculite. Moreover, the study also showed that the structure of organo-vermiculite has a significant impact on the uptake of As(III) and As(V) anions.

Effects of Supports on Pd–Fe Bimetallic Sorbents for Hg0 Removal Activity and Regeneration Performance from Coal-Derived Fuel Gas

Pd–Fe bimetallic sorbents were shown to be a great potential sorbent for Hg0 removal from coal-derived fuel gas. In this work, activated carbon (AC), Al2O3, and Beta molecular sieve were chosen as supports to disperse Pd–Fe bimetallic components. The effects of the supports on Hg0 removal of Pd–Fe bimetallic sorbents were evaluated using a fixed-bed reactor at 200 °C. The regeneration performance of sorbents was also investigated. The results showed that Hg0 removal activity and regeneration performance over Pd–Fe/AC was the best, followed by Pd–Fe/Beta, and Pd–Fe/Al2O3. The Hg0 removal efficiency of Pd–Fe/AC bimetallic sorbents remained above 80% within 400 min after regeneration 4 times. The Pd–Fe bimetallic sorbents were characterized by N2 adsorption–desorption, Fourier transform infrared spectroscopy, X-ray diffraction, CO pulse adsorption, Hg temperature-programmed thermal desorption, and X-ray photoelectron spectroscopy. The analysis results revealed that three sorbents had a similar Hg0 removal me...

Sorption of chlorinated hydrocarbons from synthetic and natural groundwater by organo-hydrotalcites: Towards their applications as remediation nanoparticles

Chlorinated hydrocarbons (CHCs) are recalcitrant compounds frequently found as contaminants in groundwater. Hydrotalcites (HT) have emerged as promising sorbents due to their tunable properties and anion exchange capacity. Here, two types of organo-HT were synthesized, via coprecipitation, by intercalation of two different anionic surfactants, sodium dodecyl sulfate and sodium 1-dodecane sulfonate. These compounds were first characterized by a suite of techniques to quantify surfactant intercalation and to evaluate their physico-chemical properties. Next, the sorption affinity of these organo-HT towards a suite of CHCs was tested under various conditions, including interlayer surfactant type, single and multiple CHCs systems, and different water chemistry (pH, ionic composition). Sorption coefficients (Kd) and organic-matter-normalized partition coefficient (Kom) derived from linear sorption isotherms for individual CHC were inversely correlated to their hydrophobicity in the order of: tetrachloroethylene > tetrachloromethane > trichloroethylene> 1,1,2-trichloroethane > trichloromethane. Kom values were further affected by the organo-HT drying process. In contrast, varying water chemistry and pH, and the co-existence of multiple CHCs had little effect on Kom values, indicating that competition between CHCs and ionic strength have a marginal effect on the sorption affinity. The inverse linear relationship between CHC hydrophobicity and Kom is shown to be a suitable tool to predict organo-HT's sorption efficiency in complex CHCs contaminated groundwaters. Overall, organo-HT's might be used as potential sorbents for ex situ treatment of CHCs in groundwater.

Fabrication of Layered Double Hydroxide/Silica Foam Nanocomposites and Their Application for Removing Pb(II) and Cr(VI) from Aqueous Solutions

AbstractIn the current work, nanocomposites of Mg−Al and Mg−Fe layered double hydroxides (LDHs) anchored on silica foam (SF), denoted as MAL/SF and MFL/SF, respectively, were fabricated using a two‐step route. The obtained LDHs/SF nanocomposites were characterized by XRD, TEM, SEM, EDS, elemental mapping, and N2 adsorption‐desorption techniques. Sorption of the heavy‐metal Pb(II) and Cr(VI) on the LDHs/SF was determined at 25 °C and pH 5.5 using a batch technique. In comparison with bulk Mg−Al and Mg−Fe LDHs, the LDHs in the MAL/SF and MFL/SF exhibit significantly enhanced sorption capacities. In addition, the LDHs/SF nanocomposites show a good recyclability for removing heavy metals. The construction of LDHs/SF nanocomposites is an effective strategy for improving the sorption capacity of LDHs, and the nanocomposites are potential sorbents for wastewater treatment.

Uranium extraction using hydroxyapatite recovered from phosphorus containing wastewater

A considerable amount of uranium (U(VI))-containing industrial wastewater is generated from both uranium mining and processing, and nuclear electrical power generation. Discharge of U(VI) containing wastewater causes severe damage to the environment and leads to a loss of resources. Uranium sorption on hydroxyapatite (HAP) has been studied extensively to address the abovementioned issues. In the present study, BC-HAP was recovered through phosphate sorption from wastewater, which was first reused as a potential sorbent for extracting uranium from aqueous solutions comparing to commercially available nano-HAP. The sorption behavior of uranium and its transformation on the recovered BC-HAP were investigated by conducting batch experiments as well as Fourier-transform infrared, scanning electron microscopy, and x-ray diffraction analyses. BC-HAP had superior sorption ability for uranium extraction. Autunite precipitant at nano-scale is observed after uranium sorption. Partial desorption of uranium was observed in the presence of Na2CO3 and NaHCO3. Surface complexation and phosphate dissolution precipitation contributed to the favorable uranium sorption. Thus, recovered BC-HAP can be widely used as a promising and cost-effective adsorbent to extract uranium from aqueous solution.

Gamma radiation induced preparation of polyampholyte nanocomposite polymers for removal of Co(II)

A series of polyampholyte nanocomposite biopolymers, poly(N,N-diallyldimethylammonium chloride-co-acrylamide) grafted on carboxymethylcellulose/iron(III) oxide [P(DADMAC-AAm)CMC/Fe2O3] and poly(N,N-diallyldimethylammonium chloride-co‐sodium acrylate) grafted on carboxymethylcellulose/iron(III) oxide [P(DADMAC-SA)CMC/Fe2O3], was prepared with different molar ratios of anionic groups to cationic groups using gamma irradiation. The grafting properties and swelling behavior were investigated as a function of grafting conditions such as DADMAC, AAm, SA, and CMC concentrations and absorbed dose. Fourier transform infrared spectroscopic analysis (FTIR) confirmed the graft copolymerization. Scanning electron microscope (SEM) was employed to check the morphological structure of CMC, P(DADMAC-AAm)CMC/Fe2O3, and P(DADMAC-SA)CMC/Fe2O3. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) further characterized the grafted copolymers and showed their high thermal stability. Using batch sorption experiments and 60Co as a radiotracer, P(DADMAC-AAm)CMC/Fe2O3 and P(DADMAC-SA)CMC/Fe2O3 were evaluated for Co(II) removal from aqueous solutions. Experimentally, P(DADMAC-AAm)CMC/Fe2O3 and P(DADMAC-SA)CMC/Fe2O3 show high sorption capacity of Co(II), i.e. 69.67 mg g−1 and 75.17 mg g−1, respectively, which makes them potential sorbents for Co(II) removal from water/wastewater. Finally, the Co(II) sorption was examined using sorption isotherm and kinetic models. Cobalt sorption was best fitted to Langmuir model which suggests the sorption is of chemisorption type. On the other hand, the sorption kinetics was best represented by the pseudo-first-order kinetic model.

Investigation on elemental mercury removal by cerium modified semi-coke

Coal-fired power plant is the largest anthropogenic mercury source. Active carbon injection technique has been widely used to control the mercury emissions. However, high operation cost limits its development and it is necessary to find other potential mercury sorbents. In this study, raw semi-coke and a series of novel cerium (Ce) modified semi-cokes were synthesized and utilized for removing elemental mercury (Hg0) from simulated flue gas. It is noteworthy that the efficiencies were tested without hydrogen chloride (HCl) in order to evaluate the sorbents efficacy for low-chlorine (Cl) coal. The results show that the modified sorbents exhibited the best performance at 150 °C. The performance of sorbent could be reinforced due to the existence of oxygen (O2), nitric oxide (NO) and HCl. The adverse effect caused by sulfur dioxide (SO2) reduced dramatically after Ce modification. The negative impact of ammonia (NH3) on Hg0 removal in this study could be neglected owing to the tiny concentration of NH3. Raw semi-coke provided sufficient carbon content, which is favorable to mercury adsorption. As Ce loading increased, the carbon structure changed and the crystal of cerium oxide was formed in the modified semi-coke. The mass fraction of cerium oxide on the sorbent was over 4.4% when the concentration of Ce modification solution was higher than 0.2 mol L−1. The redox reaction activity and the oxygen storage ability of Ce3+/Ce4+ gave a huge boost to the performance of modified semi-coke. The addition of Ce also had an impact on the proportion of oxygen species.

Flower waste: a novel candidate for the removal of chromium from tannery effluent

Chromium is a highly abundant element and is present in its ionic form in most of the effluent streams. As a consequence, improved and innovative methods of waste water treatment have been developed to remove these metal ions. In this work we used flower waste biomass as a biosorbent to remove Cr from tannery effluent through column experiments. The sorption capacities of biosorbent (fine, coarse and rough grades) were also evaluated by employing chemical pretreatments viz., sodium hydroxide, acetic acid, glutaraldehyde and hydrogen peroxide. The order of percentage removal of Cr using the above pretreatments is: 10% hydrogen peroxide < raw powdered-FWB < 2% glutaraldehyde < 10% acetic acid < 0.1 N sodium hydroxide. Among the different grades of biosorbents used, fine grade adsorbed more Cr (70%) than that of coarse (64%) and rough (62%) sorbents. The removal percentage of Cr from tannery was analysed by using atomic absorption spectroscopy, the functional groups which are responsible for adsorption was examined by Fourier transform-infrared spectroscopy and the amorphous behaviour of FWB facilitating metal biosorption was indicated by the X-ray diffractogram. This study showed that pretreated flower waste biomass is a potential sorbent of Cr, which could be successfully used to reduce the Cr content in tannery effluent.

Sorption properties of peroxidase-catalysed polyphenolic resin enable aromatics’ capture

Soybean peroxidase catalyses the removal of many phenols and anilines through polymerisation and precipitation. The precipitates might sorb other wastewater compounds simultaneously through a hydrophobic interaction. To model this interaction, phenol was chosen as the substrate and 4-(phenylazo)benzoate as the sorbate, and the system was quantitatively evaluated with the Langmuir isotherm. Sorption occurred either during or after enzymatic conversion of phenol (dynamic or static, respectively). The two systems showed Langmuir association constants of 0·088 and 0·13 l/mg and maximum sorption capacities of 51 and 16 mg/g, respectively. Both parameters compare favourably with those for the sorption of benzene, toluene and xylenes on activated carbon. A composite Langmuir parameter, (maximum capacity/dissociation constant), is suggested as the criterion for evaluating potential sorbent–sorbate couples. The model system demonstrates the feasibility of using enzymatically generated phenolic precipitates to remove toxic hydrophobic aromatic non-substrates from wastewater, when they co-occur with a substrate such as phenol. In the future, the use of polyaryl sorbents for aryl sorbates should be more broadly characterised and the criterion used for comparison should be the composite Langmuir parameter.

Development of reusable mercury sorbents for an oxy-fuel IGCC power generation system

Gaseous elemental mercury (Hg0) removal tests, using copper-based sorbents (CBS) developed in-house, were performed in a laboratory scale fixed-bed reactor. The aim was to find potential candidate sorbents to use in a dry syngas purification process plant. The dry purification process is under development for oxy-fuel integrated gasification combined cycle (IGCC) power generation with an efficient carbon dioxide separation function. The performance of CBS was evaluated as a function of two major characteristics. First, Hg0 removal performance of the CBS is improved by pre-sulfidation. Second, Hg0 removal performance of the spent CBS is recovered through moderate heating under diluted O2 conditions. A honeycomb type sorbent was prepared by impregnating raw material of the CBS onto the honeycomb-shaped support. Since copper sulfide will effectively capture Hg0 in a reducing gas atmosphere, the CBS honeycomb was initially pre-sulfurized by H2S diluted with N2 at 120 °C in a fixed-bed reactor until complete breakthrough of H2S. The simulated syngas from the oxy-fuel IGCC was fed into the reactor with conditions set at 140 °C and 0.98 MPa, where the Hg0 in the syngas was reduced to below 1.0 µg/m3N by the CBS honeycomb. The spent CBS honeycomb was regenerated by introducing 1 vol-% of O2 diluted with N2 at 280 °C. The sequential operation of pre-sulfidation, mercury removal, and regeneration steps was performed cyclically three times, during which the CBS honeycomb maintained a satisfying Hg0 removal performance. These results revealed that the A-CBS honeycomb is a potential candidate for the dry mercury removal process in the Oxy-fuel IGCC power generation plant.