Low Sorption Capacity Research Articles

Fabrication Of Carbon Aerogels From Coir For Oil Adsorption

Coir, known as coconut fibers, are an abundant cellulosic source in Vietnam, which are mostly discarded when copra and coconut water are taken, causing environmental pollution and waste of potential biomass. In this research, carbon aerogels from chemically pretreated coir were successfully synthesized via simple sol-gel process with NaOH-urea solution, economical freeze-drying, and carbonization. The samples, including pretreated coir, coir aerogels, and carbon aerogels, are characterized using FTIR spectroscopy, SEM, XRD spectroscopy, and TGA. The carbon aerogels exhibit low density (0.034–0.047 g/cm3), high porosity (97.63–98.32 %), and comparable motor oil sorption capacity (22.71 g/g). The properties of carbon aerogels are compared with those of coir aerogels, indicating such better values than those of coir aerogels. Coir-derived carbon aerogels is a potential replacement for the hydrophobically-coated cellulose aerogels in term of treating oil spills.

Fe-Co controlled super-hygroscopic hydrogels toward efficient atmospheric water harvesting.

Extracting atmospheric moisture for freshwater production is an appealing way to mitigate the global water crisis. However, the low moisture sorption capacity and high desorption temperature are the major bottlenecks for efficient atmospheric water harvesting. Herein, we develop a transition metal super-hygroscopic hydrogel by an economical strategy, which is constructed through a facile coordination between metal salts and ethanolamine. When the empty electron orbital of the metal ion is coordinated with the lone electron pair of nitrogen or oxygen atom, the water active sorption site is formed. A single water layer is bonded on the sites by a coordination effect, followed by physical interaction with water to form multi-layer structures. The Fe and Co ions in the hydrogel function as dual sorption sites to capture moisture, which can harvest additional water by the synergistic effect of bimetals. As a result, the bimetal hydrogel contributes to a high water uptake of 5.22 g g-1 at 95% RH, triggering the desorption process by one solar intensity due to its low desorption temperature (≤50 °C).

Sorption-desorption of some transition metals, boron and sulphur in a multi-ionic system onto phyto-biochars prepared at two pyrolysis temperatures.

The sorption-desorption of transition metals, B and S onto phyto-biochars prepared from lantana, pine needles and wheat straw by pyrolysis at 300 °C and 450 °C were studied using the batch method. Their sorption-desorption onto phyto-biochars conformed to Freundlich isotherms. Phyto-biochars pyrolyzed at 450 °C had higher sorption capacity for transition metals (Zn, Cu, Fe, and Mn) but lower sorption capacity for S as compared to those pyrolyzed at 300 °C. The desorption capacity of phyto-biochars pyrolyzed at 450 °C for transition metals, B and S was also higher than that of phyto-biochars pyrolyzed at 300 °C except for S in pine needle biochar. Percent desorption of all transition metals, B and S was lower for phyto-biochars pyrolyzed at 450 °C compared to those pyrolyzed at 300 °C; however, an opposite trend was noted for Mn and S in the case of pine needle and wheat biochars, respectively. Simple correlation analysis of Freundlich model constants, desorption index and percent desorption values of transition metals, B and S with the properties of phyto-biochars and changes in Fourier transform infra-red spectra after sorption revealed that several conjunctive mechanisms such as cation exchange, complexation and co-precipitation for the sorption of transition metals, H-bonding/ligand exchange for B and H-bonding/cation bridging for S were operative in phyto-biochars. Phyto-biochars produced from plant biomass wastes by pyrolysis at 300 °C, which have been enriched with Zn, Cu, Fe, Mn, B and S may serve as a potential slow-release nutrient carrier in agriculture.

Gas desulfurization adsorption technology

Adsorption technologies used for gas desulfurization are a widespread technique which, due to its relative simplicity, are widely used to the purification smaller volumes of gas. However, for their trouble-free and economical use, it is necessary to respect several basic requirements for the selection of suitable types of adsorbents with respect to the specific composition of the purified gas. The article provides a brief overview of the history of the development of adsorption technologies and also provides several different examples of the operational use of this technology for the purification of gases containing high concentrations of sulfur substances. Furthermore, the principles of correct selection of a suitable adsorbent for specific application cases are also specified here. Iron oxide adsorbents were used in the early times of the operation of the technology, which were inexpensive but had a relatively low sorption capacity for sulfur compounds. Therefore, sorbents based on iron oxides have been gradually replaced by more powerful, but also more expensive sorbents based on activated carbon. Initially, activated carbon without impregnation was used, the production of which took place in the Czech Republic on an industrial scale. By the further development of impregnated types of activated carbon and their introduction into industrial production, these adsorbents have been also used in adsorption technologies intended for gas desulfurization. Their sorption capacity is much higher in comparison with non-impregnated types of activated carbon, because the impregnants used convert sulfur compounds from gas into non-volatile substances (elemental sulfur, sulfides, polysulfides). This ensures a long service life of the adsorbent and high efficiency of gas purification from sul-fur substances.

Leaching Potential of Phosphite Fertilizer in Sandy Soils of the Southern Coastal Plain, USA

Novel biotechnology on transgenic plants capable of metabolizing phosphite (Phi), a reduced form of P, could improve the effectiveness of P fertilizers and reduce the P footprint in agriculture with the benefit of suppressing weed growth. However, potassium Phi (K-Phi) salts used as fertilizer are highly soluble in water. At the same time, sandy soils of the Southern Coastal Plain are vulnerable to leaching losses resulting from long-term Pi fertilizer application. We performed a replicated leaching trial using five soil materials that included three surface and two subsurface layers from cultivated topsoil (Ap horizon) with contrasting Phi and Pi sorption capacities. Each soil received three treatments K-Phi at rates 0 (control), 24, and 49 kg P ha−1 and leached twice with de-ionized water. All K-Phi-treated soils leached Phi except for the controls. A phosphorus saturation ratio (PSR) calculated from P, Al, and Fe in acid extracts indicated increasing environmental risk of Phi leaching in soils with lower Phi and Pi sorption capacities at rising rates of applied K-Phi. Because plants rapidly absorb Phi, further studies on the environmental impact of K-Phi fertilizer use should include the interaction of plants with soil properties and soil microbial activity at optimal Phi application rates for growing transgenic plants able to use Phi as a nutrient source.

Adsorption and Release Characteristics of Purified and Non-Purified Clinoptilolite Tuffs towards Health-Relevant Heavy Metals

The occurrence of health-relevant contaminants in water has become a severe global problem. For treating heavy-metal-polluted water, the use of zeolite materials has been extended over the last decades, due to their excellent features of high ion exchange capacity and absorbency. The aim of this study was to assess the effect of heavy metal uptake of one purified (PCT) and two non-purified clinoptilolite tuffs (NPCT1 and NPCT2) in aqueous solutions on monovalent ions Ni+, Cd+, Cs+, Ba+, Tl+, and Pb+. Experiments were furthermore carried out in artificial gastric and intestinal fluids to mimic human digestion and compare removal efficiencies of the adsorbent materials as well as release characteristics in synthetic gastric (SGF) and intestinal fluids (SIF). Batch experiments show low sorption capacities for Ni+ and Cd+ for all studied materials; highest affinities were found for Ba+ (99–100%), Pb+ (98–100%), Cs+ (97–98%), and Tl+ (96%), depending on the experimental setup for the PCT. For the adsorption experiments with SGF, highest adsorption was observed for the PCT for Pb+, with an uptake of 99% of the lead content. During artificial digestion, it was proven that the PCT did not release Ba+ cations into solution, whereas 13,574 ng·g−1 and 4839 ng·g−1 of Ba+ were measured in the solutions with NPCT1 and NPCT2, respectively. It was demonstrated that the purified clinoptilolite tuff is most effective in remediating heavy-metal-polluted water, particularly during artificial digestion (99% of Pb+, 95% of Tl+, 93% of Ba+). In addition, it was shown that the released amount of bound heavy metal ions (e.g., barium) from the non-purified clinoptilolite tuffs into the intestinal fluids was significantly higher compared to the purified product.

Transitional metal-doped aluminum fumarates for ultra-low heat driven adsorption cooling systems

Solid-gas adsorption has drawn considerable attention utilizing low-grade waste heat and environment-friendly refrigerants for cooling, heating, and air-conditioning. However, low sorption capacity of the adsorbents is a long-standing challenge for achieving highly efficient adsorption heat pumps. This study aims to analyze and compare the performance of green synthesized transitional metal (10% Ni and 10% Co) doped aluminum fumarate metal-organic frameworks as adsorbent materials in an adsorption chiller where water is considered as the refrigerant. Water uptakes on these adsorbents were measured at 303 K, 323 K, and 343 K gravimetrically. It was found that both Ni and Co-doped samples showed higher equilibrium uptake when compared with the parent sample while the adsorption isotherm moved towards the lower pressure region. Additionally, adsorption cycles involving the pressure, temperature, and uptakes (P-T-q diagrams) were drawn to investigate their cyclic performances. The specific cooling effects were also calculated and compared among the associated adsorbent/adsorbate pairs having the adsorption, desorption, evaporator, and condenser temperatures considered as 303 K, 353 K, 288 K, and 308 K, respectively. Additional studies were conducted using the inverse gas chromatography technique to investigate the relation between the surface properties and the water adsorption isotherms.

Migration and transformation of Sb are affected by Mn(III/IV) associated with lepidocrocite originating from Fe(II) oxidation

Antimony (Sb) is a recognized priority pollutant with toxicity that is influenced by its migration and transformation processes. Oxidation of Fe(II) to Fe(III) oxides, which is a common phenomenon in the environment, is often accompanied by the formation of Mn(III/IV) and might affect the fate of Sb. In this study, incorporated Mn(III) and sorbed/precipitated Mn(III/IV) associated with lepidocrocite were prepared by adding Mn(II) during and after Fe(II) oxidation, respectively, and the effects of these Mn species on Sb fate were investigated. Our results indicated that the association of these Mn species with lepidocrocite obviously enhanced Sb(III) oxidation to Sb(V), while concomitantly inhibiting Sb sorption due to the lower sorption capacity of lepidocrocite for Sb(V) than Sb(III). Additionally, Mn oxide equivalents increased in the presence of Sb, indicating that Sb oxidation by Mn(III/IV) associated with lepidocrocite was a continuous recycling process in which Mn(II) released from Mn(III/IV) reduction by Sb(III) could be oxidized to Mn(III/IV) again. This recycling process was favorable for effective Sb(III) oxidation. Moreover, Sb(V) generated from Sb(III) oxidation by Mn(III/IV) enhanced Mn(II) sorption at the beginning of the process, and thus favored Mn(III/IV) formation, which could further promote Sb(III) oxidation to Sb(V). Overall, this study elucidated the effects of Mn(III/IV) associated with lepidocrocite arisen from Fe(II) oxidation on Sb migration and transformation and revealed the underlying reaction mechanisms, contributing to a better understanding of the geochemical dynamics of Sb.

Mesoporous ball-milling iron-loaded biochar for enhanced sorption of reactive red: Performance and mechanisms

In order to solve the low sorption capacity of pristine biochar for anionic pollutants, e.g., reactive red 120 (RR120), a novel mesoporous Fe-biochar composite was fabricated in this study by combination of Fe-loading and ball-milling methods. The ball-milling Fe-biochar composite could effectively remove RR120 by up to 90.1 mg g−1 at pH of 7.5, and slightly alkaline condition was preferred. Adsorption kinetics showed that ball-milling Fe-biochar composite could quickly sorb RR120 with the rate constant (k2) of 2.07 g mg−1 min−1 (pH = 7.5). Positive surface charge and large surface area were responsible for the outstanding removal performance of RR120 by ball-milling Fe-biochar composite: (1) The adscititious Fe would be converted to β-FeOOH during pyrolysis, which significantly improved the zeta potential of biochar and thus facilitated the electrostatic adsorption for RR120, which contributed to 42.3% and 85.5% at pH of 3 and 7.5, respectively; (2) Ball-milling effectively increased the specific surface area and uniformed the pore size distribution, which could provide more sorption sites and expedite the diffusion of RR120 molecules, shortening the time from several hours to less than 15 min. Findings of this study not only provide a feasible modification method for biochar to adsorb anionic pollutants efficiently and rapidly, but also help to reveal the roles of Fe-loading and ball-milling in enhancing adsorption capacity.

SORPTION OF MANGANESE (II) AND VANADIUM (IV) CATIONS BY TAGAN BENTONITE IN AN AQUEOUS MEDIUM

The process of sorption of Mn2 + and V4 + cations by bentonite of the Taganskoye deposit studied depending depending on various factors (T, oC; τ, min; S: L ratio; CMn and CV, mg / l). It was found that bentonite exhibits sorption properties with respect to the studied cations in a wide range of pH values ​​(from 1 to 10). The highest degree of their sorption is achieved at the consumption of bentonite 1.5 g per 100 wt. h. metal-containing solution. The influence of the nature of the cation on the sorption capacity of Tagan bentonite was established. The most intense increase in the degree of sorption of manganese (II) occurs in 15 min with an increase in temperature to 35оС. The highest degree of sorption of V4 + cations is achieved in 60 min at 25 ° C in weakly concentrated vanadium-containing solutions (50 mg / L V4 +). Bentonite from the Tagan deposit exhibits a lower sorption capacity with respect to V4 + cations as compared to Mn2 + cations, which is due to the nature of the cation.

Preparation of hybrids of wood sawdust with 3-aminopropyl-triethoxysilane. Application as an adsorbent to remove Reactive Blue 4 dye from wastewater effluents

BackgroundBiomass-based materials present low sorption capacity. In order to overcome this disadvantage, chemical modification of these materials is required. MethodsHybrids of biomass-based materials were obtained by reacting (25%-200% weight) 3-aminopropyl-triethoxysilane (APTES) with the biomass Ayous wood sawdust (AW), obtaining the hybrid materials AW@APTES-0.25, AW@APTES-0.50, AW@APTES-1.0, AW@APTES-1.5, and AW@APTES-2.0, that were characterized by hydrophobic/hydrophilic balance, CHN elemental analysis, surface area, TGA, FTIR, and pHpzc. Significant findingsFor screening purposes, the five materials were tested as adsorbents to remove reactive blue 4 (RB-4) from water. The results showed that AW@APTES-0.5 attained the maximum removal of RB-4. The kinetics and equilibrium data were suitably fitted by the nonlinear General-order kinetic (GO) and Liu equilibrium adsorption models. The maximum amount adsorbed of RB-4 dye was 415.1 mg g − 1 using AW@APTES-0.5 (50 °C). An increase in the Qmax value of AW@APTES-0.5 concerning unmodified AW attained up to 21.6 times. The ΔG° and ΔH° indicated that the adsorption processes of RB-4 onto adsorbents are endothermic and spontaneous, and the magnitude of enthalpy of adsorption (25.10 kJ mol−1) is compatible with the electrostatic attraction mechanism. The adsorbents’ applicability for treating simulated dye effluents showed an excellent efficiency attaining 98.66% removal of the effluent.

Ultrahigh-Energy-Density Sorption Thermal Battery Enabled by Graphene Aerogel-Based Composite Sorbents for Thermal Energy Harvesting from Air

Sorption-based thermal storage has drawn considerable attention for sustainable and cost-effective thermal management and energy storage. However, the low sorption capacity of sorbents is a long-standing challenge for achieving high-energy-density sorption-based thermal storage. Herein, we demonstrate an ultrahigh-energy/power-density sorption thermal battery (STB) enabled by graphene aerogel (GA)-based composite sorbents for efficient thermal harvesting and storage with record performance. Scalable GA-based composite sorbents with high salt loading are synthesized by confined calcium chloride inside a GA matrix (CaCl2@GA), showing fast sorption kinetics and a large sorption capacity up to 2.89 g·g-1 contributed by the GA matrix and chemisorption-deliquescence-absorption of CaCl2. The STB realizes thermal charging-discharging via the multistep water desorption-sorption of CaCl2@GA sorbent with the humidity from air. Importantly, the lab-scale STB exhibits record energy density of 1580 Wh·kg-1 and power density of 815 W·kg-1 for space heating. Our work offers a promising low-carbon route for efficient thermal energy harvesting, storage, and utilization. ©

Clinoptilolite and iron sorption/desorption under multiple pH conditions: Testing a substrate for passive treatment of acidic, iron-rich solutions.

Equilibrium sorption and desorption experiments were conducted with clinoptilolite to evaluate the potential sorption/desorption of iron during different pH conditions. Sorption experiments indicated a partitioning of 0% to 17% of the iron in solution given pH of 2 to 4. The pH 2 solution was able to desorb 70% of the iron that was captured from a pH 3 solution. The largest desorption and sorption of iron and corresponding pH represent the end points of iron capture primarily by sorption/exchange. These endpoints are the estimated pHpzc of 2.5 and the initial precipitation point of iron(II) at pH ~3.5. This acidity range is where clinoptilolite is able to capture iron without precipitation or the occurrence of full surface protonation. The inability of the highest acidity to remove all sorbed iron represents the greater bound iron that will not readily desorb with a change in pH. This retained iron creates a metastable state of the clinoptilolite that has a lower sorption capacity but reflects the ability of clinoptilolite to retain a sorbed transition metal with changes in pH. As pH varies, clinoptilolite may evolve in a sequence of metastable states reflective of its ability to capture or retain metals. PRACTITIONER POINTS: Clinoptilolite is a capable reactive substrate, but its sorption/exchange effectiveness at low and variable pH and ability to retain captured metals was unknown. Clinoptilolite retains its metal capture properties to a pH of 2.5 where surface protonation and mineral degradation likely occurs. The ability of clinoptilolite to retain captured iron under greater acidity reflects an evolution of its sorption/retention capacity.

Human serum albumin-imprinted polymers with high capacity and selectivity for abundant protein depletion

Depletion of human serum albumin (HSA), the most abundant protein in human plasma, from serum/plasma is a prerequisite before their proteomic analysis. Molecularly imprinted polymers (MIPs) using HSA as a template have been designed for this purpose, but suffer from a low sorption capacity and low selectivity. Here, a new HSA-imprinted polymer was synthesized using N-isopropylacrylamide (NIPAM) as the main monomer; acrylamide (AAm), methacrylic acid (MAA), and dimethylaminoethyl methacrylate (DMAEMA) as functional monomers; and oligoglutamic acid-based peptide crosslinker (PC) as a crosslinker at pH 5.5. When pH is adjusted to 7.4, the peptide chains in the polymer change from a helical conformation to an extended coil conformation, and the polymer swells. Consequently, the template protein is removed completely. When pH is adjusted back to 5.5, the peptide chains fold back precisely to the helical conformation. Both the size and shape of the imprint cavities are restored. Therefore, the polymer rebinds the template protein selectively. Highest imprinting factor (IF) was observed at pH 5.5 at which the polymer was synthesized. The IF increases with the increasing number of glutamic acid residues in the PCs because of their increased degree of helicity at pH 5.5. No improvement in imprinting effect was observed when using a peptide crosslinker containing both L- and D-glutamic acid residues and hence incapable of folding into α-helix, further confirming the key role of the pH-induced helix-coil transition of the peptide chains. The MIP synthesized here presents a much higher affinity to HSA than the nontemplate proteins. It could be used repeatedly without evident decrease in sorption capacity. Because of the mild eluting conditions, the secondary structure of the extracted HSA protein remains unchanged. Finally, the MIP was used to deplete HSA from human serum. Because of its high sorption capacity and high selectivity, HSA was depleted completely and selectively. Statement of significanceA new molecularly imprinted polymer (MIP) using human serum albumin (HSA) as a template was synthesized using N-isopropylacrylamide (NIPAM) as the main monomer; acrylamide (AAm), methacrylic acid (MAA), and dimethylaminoethyl methacrylate (DMAEMA) as functional monomers; and oligoglutamic acid-based peptide crosslinker as a crosslinker. Because of the reversible and precise pH-induced helix-coil transition of the peptide chains, the template protein was removed facilely and completely under mild conditions. Simultaneously, a significant improvement in imprinting efficiency was obtained. The sorption capacity was as high as 648.05 mg/g and the imprinting factor was 7.9. Because of its high selectivity and high binding capacity, the MIP synthesized here is highly promising for the depletion of HSA, the most abundant protein in serum, which is a prerequisite for its proteomic analysis. For the first time, complete and selective depletion of HSA from human serum was achieved using a protein-imprinted polymer.

Rapid formation of pyrogenic char (biochar) with high and low sorption capacity towards organic chemicals.

Pyrogenic char (biochar) with a high sorption capacity (B-HSC) can sequester hazardous chemicals (e.g., phenanthrene). However, when sorption inhibits bioavailability of some functional chemicals (e.g., the herbicidal efficacy of diuron in soil), biochar with a low sorption capacity (B-LSC) is required to prevent sorption effects. The pyrolytic B-HSC generation has been reported, but information on B-LSC formation is scarce. How fast B-HSC and B-LSC could be generated is unknown until now. Here, biochars were rapidly prepared (the shortest heating time reached 5min and the cooling time reached<30min) by a direct-pyrolysis method by directly exposing packaged rice straw and pine wood to 350°C, 500°C and 700°C and out-of-furnace cooling at room temperature. The sorption of diuron, phenanthrene, and twelve other chemicals was investigated. B-HSCs were obtained within 30min of rice straw pyrolysis, and the biochar Kd values quickly increased to 7-730-fold that of the raw biomass as -OH and C-O-C in (hemi)cellulose of rice straw rapidly degraded, increasing hydrophobic interactions between the char and chemicals (solubility≤82.8g/L). In contrast, B-LSCs were generated within 30min of PW pyrolysis, and the Kd values of the biochars were 0.2-3.0-fold that of the raw biomass, as the surface area development and hydrophobicity-driven sorption were probably delayed by the late degradation of lignin aromatic C-O and phenolic -OH. Biochar amendment revealed an enhancement effect of B-HSC but not of B-LSC on soil sorption. The fast formation of B-LSC and B-HSC provides a guide to develop time- and cost-effective technique in pyrolytically producing weakly or strongly sorbing biochars for organic chemical management.

Management of stormwater pollution using green infrastructure: The role of rain gardens

AbstractMajor modifications are needed in existing stormwater management practices to control floods in urban landscapes, protect natural ecosystems, and minimize infrastructural destruction due to stormwater hazards. Stormwater management combined with urban design can be the best solution to minimize urban flooding risks and promote a clean natural environment. Green infrastructure (GI) is an environmentally sustainable alternative to traditional methods of stormwater management. Rain gardens, a GI, play a vital role in reducing rainwater volume and flow, prevent asset's destruction, remove pollutants from urban runoff, and recharge groundwater. Rain gardens can remove sediments, heavy metals, pathogens, nutrients, hydrocarbons from stormwater via several mechanisms. Various amendments in soil media help in delayed saturation, low sorption capacity, limited pollutant mobility, and bioaccumulation/biotransformation of metals/organic compounds in rain gardens. Soil media and plants play a vital role in the pollutant removal processes of rain gardens. Various plant‐based mechanisms and chemical processes like adsorption, reduction, sedimentation, cation‐exchange capacity, complexation, and so forth are involved in the removal of contaminants from stormwater. Construction and design considerations; different models of rain gardens; working mechanisms; performance assessment tools like capacity tests and synthetic runoff tests; removal of stormwater pollutants, and biphasic rain gardens have been critically discussed in this review. The state‐of‐the‐art review approaches to provide fundamental knowledge of rain gardens and in‐depth analyzes its potential as a stormwater management tool. Future directions on improving efficiencies of rain gardens have also been discussed for prospective researchers.This article is categorized under: Engineering Water

Switchgrass as oil and water-spill sorbent: Effect of particle size, torrefaction, and regeneration methods

Switchgrass, both raw and torrefied, was tested for its ability to sorb water or oil. The cyclic performance was also examined, utilizing centrifugal extraction as the regeneration method. Both oil and water sorption capacity increase with the decreasing size of raw switchgrass particles. Results indicate that 3 mm raw switchgrass can sorb water at a capacity of about 6 times its mass and can sorb oil at a capacity of about 3 times its mass, which makes it a suitable biodegradable sorbent. Torrefaction at 220 °C for 30 min reduces water sorption capacity by an average of 55% but does not have a statistically significant impact on oil sorption. Sorption of liquid is negatively correlated to particle size. Centrifugation is able to partially desorb either liquid from the sorbent, and subsequent sorption cycles do not display lower sorption capacity than the first cycle when calculated on a dry mass basis.

Comparative effectiveness of activated dolomite phosphate rock and biochar for immobilizing cadmium and lead in soils

Sandy soils in Florida are vulnerable to toxic metal pollution, and it is necessary to identify desirable amendments for the remediation of metal contaminated soils. Sorption and incubation experiments were conducted to compare the effectiveness of dolomite phosphate rock (DPR), humic acid activated dolomite phosphate rock (ADPR) and biochar (BC) in immobilizing Cd2+ and Pb2+ in two representative agricultural soils in south Florida (Alfisol-Riviera and Spodosol -Ankona series). The results showed that the soils had a low sorption capacity for metals with maximum sorption of 0.767–3.30 mg/g. Application of amendments increased the maximum sorption by 4.2–4.8 times for Pb2+ and 1.5–2.2 times for Cd2+ in Alfisol soil, and 7.1–7.9 times for Pb2+ and 1.7–3.1 times for Cd2+ in Spodosol soil. ADPR was the most effective amendment for increasing the soil’s sorption capacity for Cd2+ and Pb2+. 0.01 M CaCl2 extractable metals in the contaminated soils were significantly decreased by all the amendments, especially ADPR, which reduced extractable Cd2+ and Pb2+by 87.2 and 76.0% in Alfisol and 91.3 and 76.3% in Spodosol soil as compared to control. The amounts of extractable Cd2+ and Pb2+ were negatively correlated with soil pH and available P, indicating that the change of soil characteristics by amendments was the dominant mechanism for enhanced immobilization of metals in the contaminated soils. These results indicate that ADPR has great potential for remediating toxic levels of Cd2+ and Pb2+ in contaminated soils.

DFO@EVOH and 3,4-HP@EVOH: Towards New Polymeric Sorbents for Iron(III)

The paper presents the synthesis and preliminary characterization of two novel solid-phase sorbents for iron(III), resulting from the functionalization of ethylene-vinyl alcohol copolymer (EVOH) with deferoxamine, DFO (DFO@EVOH), and a novel tripodal 3-hydroxy-4-pyridinone, named 3,4-HP (3,4-HP@EVOH). DFO and 3,4-HP have been covalently bonded to EVOH, using carbonyldiimidazole as a coupling agent. Before their use as Fe(III) sorbents, they were warm-pressed to obtain a thin film. Polymers have been characterized by conventional physico-chemical techniques; furthermore, the sorption properties towards Fe(III) were investigated. The physico-chemical characterization of the new solid-state devices demonstrates the effective linkage of the two receptors on the polymeric support. Despite a relatively low sorption capacity for both materials, the stoichiometry and the complexation constants of Fe(III)/DFO@EVOH and Fe(III)/3,4-HP@EVOH are in pretty good agreement with those obtained for the same ligands in aqueous solutions.

Removal of lead from two polluted soils by magnetic wheat straw biochars

Due to high sorption capacity for heavy metals, magnetic biochar (MBC) has the potential to adsorb heavy metals in soils, which are then removed together with MBC from soils by a magnetic field. In this study, two magnetic biochars (MBC300 and MBC700) were derived from the magnetization of wheat straw biochars pyrolyzed at 300 and 700 °C. Strong binding of Pb with iron oxide particles deposited on biochar was observed. After the MBCs (7.5%, w/w) were applied to two naturally Pb-polluted soils (named as He-soil and Hu-soil) for 720 h, the removal efficiency of Pb from the soil by MBC300 (26.8–40.1%) was similar (p > 0.05) to that by MBC700 (25.1–42.1%). This is because MBC300 has lower sorption capacity for Pb but higher recovery percentage from soils as a result of lower saturation magnetization. The removal efficiencies of Pb by the two MBCs were 13–17% higher for He-soil than for Hu-soil, which was due to higher proportion of mobile forms of Pb in He-soil (82.3%) than in Hu-soil (51.5%). Spectroscopic analysis indicated that Pb in soils tended to bind onto the surface of MBC in more stable forms. Moreover, removing Pb from soils by MBC could decrease Pb concentration in ryegrass by about 30%. Therefore, it might be a potential method to remedy Pb-polluted soils.