Greater Sorption Research Articles

Pedological factors affecting pesticide retention in a series of tropical volcanic ash soils in the French West Indies

Specific pedoclimatic conditions in tropical environments have a considerable impact on pesticide fate. Tropical volcanic soils result from specific pedogenesis processes linked to successive volcanic projections; they are characterised by acidic conditions, high organic matter content, a specific mineralogical composition and the presence of organo-mineral complexes. The retention of pesticides in these soils is therefore often high but variable depending on the associated molecules and soil properties. Nevertheless, knowledge of pesticide sorption in these soils remains limited, and knowledge of the desorption process is scarce. The objectives of this work were to study the variability of the sorption and desorption coefficient of four pesticides currently used in banana and sugarcane crops on a set of representative tropical soils developed on volcanic ash (Guadeloupe, French West Indies). Adsorption and desorption isotherms were analysed for three ionizable pesticides (2,4-D, mesotrione, glyphosate) and a hydrophobic pesticide (difenoconazole) on ten soil samples from five soil profiles: one silandic andosol, one vitric andosol, two nitisols and one ferralsol. For ionizable pesticides, soil pH appears to be a first-order discriminating factor of the sorption capacity, and the organic carbon content appears to have a lesser impact on 2,4-D. For a strongly hydrophobic pesticides such as difenoconazole, the organic carbon content plays a major role in sorption. Desorption hysteresis has been observed regardless of the soils and the molecules considered, and tropical volcanic soils seem to be conducive to adsorption but show low to moderate release. The silandic andosol, which has the greatest sorption, buffers the dissemination of pesticides towards surface and groundwaters but also increases the risk of long-term contamination in the case of molecules that degrade slowly. Moreover, our results highlight that agronomic practices, such as liming, have a major impact on the sorption coefficient of pesticides and must be considered for when predicting sorption in a tropical volcanic context.

Synthesis of Novel Nanocomposite CaO/AC/ZnO from Biogenic Wastes of Date Palm Seeds from The Najran Region (Saudi Arabia) and Eggshells for Degradation of Methylene Blue

Metal nanoparticles and activated carbon-based nanocomposite materials are gaining popularity due to their numerous potential applications in a wide range of materials science areas. The current study aims to create novel photocatalyst frameworks for nanocomposites that were synthesized from biogenic waste and used to photodegrade methylene blue (MB) in wastewater under visible light. The activated carbon from date seeds was calcinated at a temperature of 700°C for two hours, and its surface was improved using zinc oxide nanoparticles and calcium oxide nanoparticles manufactured from eggshells at 900oC. XRD, FT-IR, SEM, BET, and TEM analyses were used to characterize the produced nanocomposites. The synthesized nanocomposite photocatalytic activity was evaluated by degrading MB dyes, its model of water pollution. The results showed that the nanocomposite CaO/AC/ZnO has a mesoporous structure with great sorption capability. Also, the photodegradation efficiency of MB using AC, CaO, AC/ZnO, and CaO/AC/ZnO nanocomposite was 33.23, 37.58, 54.61, and 88.92%, respectively, after100 min of sunlight irradiation indicating that photodegradation efficiency increases by improving the surface properties of AC. The CaO/AC/ZnO nanocomposite exhibited a 96.7% removal efficiency of MB following 120 min of visible light radiation exposure. Therefore, the CaO/AC/ZnO nanocomposite has a promising opportunity to function as a versatile and effective photocatalyst for photodegradation of organic dyes in wastewater.

Physicochemical investigation of mercury sorption on mesoporous thioacetamide/chitosan from wastewater

Mercury is a toxic environmental element, so it was necessary to prepare a new, highly efficient, cheap sorbent to remove it. A mesoporous thioacetamide/chitosan (MTA/CS) was manufactured via a simplistic strategy; the chitin deacetylation to gain chitosan (CS) and the addition of thioacetamide. The as-prepared MTA/CS was characterized using X-ray diffraction, EDX, SEM, FTIR, and BET surface analysis. According to the findings, the MTA/CS was effectively synthesized. The removal behaviors of Hg2+ onto MTA/CS composite were inspected, which suggested that the MTA/CS composite exhibited great sorption properties for Hg2+ in liquid solutions. The maximal Hg2+ sorption capacity was 195 mg/g. The effects of temperature, Hg2+ concentration, contacting time, and MTA/CS concentration on sorption were analyzed. The 2nd-order model and Langmuir isotherm were suitable for the physicochemical adsorption processes. Thermodynamic analysis showed that the Hg2+ adsorption process onto the MTA/CS composite is exothermic and occurred spontaneously. The desorption condition of Hg2+ from its loaded MTA/CS was also gained. Likewise, the MTA/CS sorbent was undoubtedly regenerated by 0.8 M NaNO3 80 min contacting and 1:50 S:L ratio. The versatility and durability of MTA/CS sorbent were investigated via nine sorption-extraction cycles. The optimum parameters were applied to wastewater. Based on the result, the as-prepared MTA/CS might be a potential sorbent for removing Hg2+ from liquid solutions.

Paddle-Wheel-Shaped Porous Cu(II)–Organic Framework with Two Different Channels as an Absorbent for Methylene Blue

The destruction of the ecological environment caused by human activity and modern industrial development is so severe that the water environment has become seriously polluted. Therefore, the exploration of high-efficiency absorbents has become one of the hot topics to solve this issue. Herein, a porous metal-organic framework [Cu(L)]·2.5H2O·0.5DMF (1, DMF = N,N-dimethylformamide) was successfully constructed using a rigid N-heterocyclic 5-(4-(1H,3,4-triazol-1-yl)phenyl)isophthalic acid (H2L) ligand. In particular, its structure includes the classical paddle-wheel-shaped secondary building units and two 1D channels with diameters of 7.2 and 3.2 Å, respectively. Complex 1 shows great sorption performance for methylene blue (MB) with a maximum capacity of 589 mg·g-1. The various influence factors, including the time, dye concentration, adsorbent dosage, and the pH of the solution, are investigated respectively. Also, the adsorption process is more in line with the first-order kinetics and the Langmuir isothermal adsorption model. The strong electrostatic force and intermolecular forces are primarily responsible for the remarkable adsorption ability of MB.

Phytoremediative adsorption methodologies to decontaminate water from dyes and organic pollutants.

Persistent organic pollutants and dyes cause major problems during ecofriendly wastewater treatment. To overcome this huge problem, several techniques have been considered and in practice for the safe disposal of organic pollutants in recent years; some of them are discussed and compared herein. This review focuses on new trends for wastewater treatment and compares them with certain other techniques alongside their pros and cons; adsorption is considered the safest among them. Adsorbents derived from agri-wastes have good capacity for the removal of these contaminants owing to their great sorption capacity, high reusability, easy operation, etc. Sometimes they need some modifications for the removal of dyes, which are also discussed in this review. This capacity of adsorbents to chelate dye molecules can be affected by factors, such as pH, the concentration of dyes and adsorbents, and temperature of the system. pH has direct influence on the ionization potential and charge on the outer surface of adsorbents. The findings on isotherms, kinetics, and desorption of plant waste-based biomaterials that are safe for the ecosystem and user friendly and are used for hazardous contaminant removal from water are summarized in this review. Finally, conclusions and future perspectives are presented, and some other materials, such as CNTs and MOFs, are also discussed as efficient adsorbents for eliminating dyes from wastewater. Finally, it is predicted that the adsorption of dyes is a more feasible solution for this dye pollution problem.

Improved performance of the pyrimidine-modified porous In-MOF and an in situ prepared composite Ag@In-MOF material.

A stable porous In-MOF 1 was prepared for the first time via an asymmetric N,O-containing (2-pyrimidin-5-yl)terephthalic acid (H2L). It was found that the 1,4-benzenedicarboxylate anions (bdc2-) were formed in the synthesis process of 1. Thus, another new isomorphic In-MOF 2 was formed by employing the H2bdc ligand in the synthesis process of 1. More importantly, when adding AgNO3 in the synthesis process of 1 and 2, only composite Ag@1 was obtained via the in situ reduction of Ag(I) to Ag NPs without additional reducing agent. MOF 1 and Ag@1 had great sorption capacity; in particular, 1 had remarkable dynamic selectivity for C2H2/CH4 and CO2/CH4, and they were also efficient catalysts for fixing CO2 and epoxides. It is hoped that this work may supply an effective strategy to build stable MOFs and composite Ag@MOF materials with excellent multifunctional applications.

Sugarcane biomass as а potential carrier for drug delivery system

Non-steroidal anti-inflammatory drugs are well-known medications for reducing pain and a group of drugs that can cause mucosal damage of the stomach. The negative effects on the digestive system can be reduced by immobilization of drugs on various carriers, for instance, on the components of plant biomass, for the creation of drug delivery system. Plant biomass is a lignocellulosic complex consisting of lignin, cellulose and hemicellulose that can potentially be regarded as a carrier of pharmaceuticals. Sugarcane residues such as bagasse and straw are biomass by-products of the sugarcane industry. One of the prospective ways for their efficient utilization can include chemical processing with the aim of obtaining effective biosorbents or so-called carriers of different composition and structure. The aim of the work was to study the structural, morphological, and sorption properties of cellulose, lignin, and lignocellulose, derived from sugarcane biomass (bagasse and straw) by means of delignification and hydrolysis, as potential components for drug delivery system. Sugarcane straw samples show higher densities in comparison with bagasse samples. Both lignin samples from bagasse and straw have greater bulk and true density if compared to other materials from sugarcane biomass of cellulosic and lignocellulosic nature. The increase in adsorption pore volume in lignins is observed, being indicative of better sorption ability. Both samples of cellulose and lignocellulose from straw have greater pore structure if compared to the initial material. The values of sodium diclofenac sorption efficiency correlate with the values of pore volume for corresponding materials. Lignin from sugarcane straw, which shows greater porosity, has greater sorption properties. SEM images show that the initial materials and treated materials have complex morphology. FTIR spectra show a clear difference in the structure of lignocellulose, cellulose, and lignin from sugarcane bagasse and straw. The potential application of biopolymers from bagasse and straw as organic carriers of sodium diclofenac was studied. With this purpose, plant polymers were impregnated with an alcoholic solution of sodium diclofenac and the desorption process was investigated. The lignin sample from sugarcane straw has a longer period of drug release, which indicates the obtained effect of prolongation.

Transient reaction phenomena of sorption-enhanced steam methane reforming in a fixed-bed reactor

The transient chemical reaction phenomena of the sorption-enhanced steam methane reforming (SE-SMR) by using Ni/Al2O3 catalyst and CaO sorbent in a tubular fixed-bed reactor were numerically investigated by an experimentally verified unsteady 2D model. Four chemical reactions are involved in SE-SMR including steam reforming (SR), water gas shift (WGS), global steam reforming (GSR), and CO2 sorption. The reaction process in time is divided into period 1, transient period, and period 2. The high-purity H2 is produced in period 1 which is defined as the outlet molar fractions of H2 ≥ 90% and CO ≤ 1% (dry basis) in this work. In the first half of period 1, the endothermic reaction rates of SR and GSR are dominant in the entrance region of catalyst/sorbent bed. The WGS and CO2 sorption reactions are triggered by SR and GSR reactions. The heat transfer from the wall plays an important role. Higher CaO conversion, temperature, and reaction rates appear first near the wall region, then they gradually expand to the central region.In the second half of period 1, a sharp wave-shaped curve of strong CO2 sorption reaction occurred in downstream becomes dominant and it moves to downstream almost at a constant speed, as time progresses. The peak value of the CO2 sorption reaction is more than twice larger than that of SR or WGS. The SR and WGS reaction rates are significantly enhanced by CO2 sorption reaction. The great sorption, WGS, and SR reactions result in a high-purity H2 production with the outlet molar fractions of 95.8% H2, 0.998% CO, and 0.73% CO2 at the end of period 1, based on the parameters used in this work such as reactor temperature of 600 °C. The maximum CaO conversion is about 76% in end of period 1 and the average CaO conversion in the reactor is 51%. The 2D distributions of CaO conversion, temperature, and reaction rates are also presented and discussed.

Indaziflam sorption–desorption and its three metabolites from biochars- and their raw feedstock-amended agricultural soils using radiometric technique

This study aimed to characterize the effect of amending soils with biochars derived from soybean residues, sugarcane bagasse, and wood chips on the sorption–desorption of indaziflam and indaziflam-triazinediamine (FDAT), indaziflam-triazine-indanone (ITI), and indaziflam-carboxylic acid (ICA) metabolites applied to soils from three Midwestern U.S. states, a silt loam and a silty clay loam. Biochars produced from different feedstock were used as soil amendments and compared with raw feedstock. Sorption–desorption experiments of indaziflam and its three metabolites were performed using the batch equilibration method and analyzed for 14C activity by liquid scintillation counting (radiometric technique). In all soils, the use of organic amendments promoted greater sorption and less desorption of indaziflam and ITI. The addition of biochar to soils promoted greater sorption of the four tested chemical products compared with the corresponding raw materials. Among the biochars, grape wood chips showed greater potential in sorb indaziflam and ITI. In general, none of the biochars affected the sorption and desorption of FDAT and ICA. Characterization of biochar to be used as a soil amendment (immobilizer) is highly recommended prior to field addition to optimize the sorption process and to prevent increased soil and water contamination of indaziflam and its metabolites following biochar addition.

Development of an acidized biochar-supported hydrated Fe(III) oxides for highly efficient cadmium and copper sequestration from water

Biochar-supported metallic oxides are attractive adsorbents for heavy metal cleanup, but the adsorption performance is still unsatisfactory as a result of the self-aggregation of the incorporated metallic oxides. A new hybrid nano-material was prepared through impregnating hydrated ferric oxide (HFO) nanoparticles within biochar bearing high-density charged oxygen-containing groups (e.g., carboxyl and hydroxyl groups) (ABC) derived from HNO3 treatment. The as-made adsorbent, denoted as HFO-ABC, possesses highly dispersed HFO nanoparticles with typical size lower than 20 nm, and exhibits greater sorption capacity for Cd(II) and Cu(II) than the pristine biochar-supported HFO. It also shows great sorption preference toward Cd(II) and Cu(II) in co-presence of high levels of Ca2+, Mg2+ and humic acid (HA). Such prominent performance is put down to the high-density charged functional groups on the host ABC, which not only promote the dispersion of the immobilized HFO nanoparticles but also generate the potential Donnan membrane effect, i.e., the pre-concentration and permeation of target metals prior to their preferable adsorption by nano-HFO. The predicted effective coefficients of intra-particle diffusion for Cu(II) and Cd(II) are 3.83 × 10−9 and 4.33 × 10−9 cm2/s, respectively. HFO-ABC exhibits excellent performance for fixed-bed column application, and yields 513 and 990 BV effluents for Cd(II) and Cu(II) to achieve their discharge standards, respectively. The spent HFO-ABC could be in situ regenerated using binary HCl-CaCl2 solution with desorption efficiency higher than 95%. All results manifest that increasing charged functional groups via HNO3 treatment is an effective measure for boosting sorption performance of biochar-based nanocomposites.

Features of the two-stage formation of macroporous and mesoporous silicon structuresя

The aim of this work was the formation of multilayer structures of macroporous silicon and the study of their structural, morphological, and optical properties in comparison with the properties of multilayer structures of mesoporous silicon. The paper presents the results of the development of techniques for the formation of multilayer structures of porous silicon por-Si by stepwise change in the current with two-stage modes of electrochemical etching.The data on the morphology, composition, and porosity of macroporous and mesoporous silicon samples were obtained using scanning electron microscopy, IR spectroscopy, and X-ray reflectivity. It was shown that with the two-stage growth of porous silicon layers, the depth of the boundary between the layers of the structure was determined by the primary mode of electrochemical etching, while the total layer thickness increased with an increase in the current density of electrochemical etching.A comparative analysis of the relative intensity and fine structure of vibrational modes of IR spectra indicated a significantly more developed specific pore surface and greater sorption capacity of mesoporous silicon as compared to macroporous silicon.
 
 
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Removal of two cytostatic drugs: bleomycin and vincristine by white-rot fungi \u2013 a sorption study

PurposeCytostatic drugs cannot be easily removed by conventional sewage treatment plants, resulting in their ultimate release into aquatic systems where they become a threat. Thus, new technologies which can be used to eliminate these drugs more effectively before they enter the environment are increasingly important. Fungal treatment of wastewaters is a promising and environmentally friendly technology for pharmaceutical remediation. The aim of this work is to examine the biosorption of two cytostatics, bleomycin and vincristine, in the aqueous solution by fungal biomass.MethodsFive white-rot fungi were used in this study: Fomes fomentarius (CB13), Hypholoma fasciculare (CB15), Phyllotopsis nidulans (CB14), Pleurotus ostreatus (BWPH), and Trametes versicolor (CB8). Tests were conducted on different types of biomass (alive and dead – autoclaved) and in various physico-chemical conditions: varied drug concentrations (5, 10 and 15 mg/L), temperatures (from 15.4 to 29.6 °C), and pH (from 3.2 to 8.8).ResultsThe results showed that among alive biomass, T. versicolor (CB8) had the greatest sorption ability for bleomycin and P. nidulans (CB14) worked best for vincristine. The tested sorption process could be described by a pseudo-second order kinetics model. Sorption equilibrium studies demonstrated that for bleomycin Redlich-Peterson, while for vincristine Langmuir model fitted best. The thermodynamic studies showed that the sorption process was endothermic chemisorption for bleomycin, and exothermic physisorption for vincristine. For both drugs the sorption ability increased with an increase of the pH value.ConclusionThe biosorption on fungal biomass is a favorable alternative to conventional wastewater treatment processes for anticancer drug removal.

Highly Hydrophobic Polydimethylsiloxane-Coated Expanded Vermiculite Sorbents for Selective Oil Removal from Water.

Naturally abundant vermiculite clay was expanded by using an aqueous solution of H2O2 and its surface was modified with ultra-thin polydimethylsiloxane (PDMS) using facile thermal vapor deposition to prepare an ecologically friendly, low-cost oil sorbent that plays an important role in oil spillage remediation. The resulting PDMS-coated expanded vermiculite (eVMT@PDMS) particles exhibited adequate hydrophobicity and oleophilicity for oil/water separation, with numerous conical slit pores (a size of 0.1–100 μm) providing a great sorption capacity and an efficient capillarity-driven flow pathway for oil collection. Simply with using a physically-packed eVMT@PDMS tube (or pouch), selective oil removals were demonstrated above and beneath the surface of the water. Furthermore, these sorbents were successfully integrated and then applied to the advanced oil-collecting devices such as a barrel-shaped oil skimmer and a self-primed oil pump.

Ciprofloxacin increased abundance of antibiotic resistance genes and shaped microbial community in epiphytic biofilm on Vallisneria spiralis in mesocosmic wetland

This study investigated the fate of ciprofloxacin (CIP) in wetlands dominated by Vallisneria spiralis. About 99% of CIP was degraded from overlaying water within 4 days of treatment but significantly inhibited the nutrient removal capacity (TN, TP, and COD) by causing a drastic reduction in microbial aggregation in epiphytic biofilm and bacterial biodiversity. CIP triggered resistance mechanisms among dominant bacteria phyla such as Proteobacteria, Actinobacteria, and Planctomycetes causing their increased relative abundance. Additionally, the relative abundances of eukaryotic microorganisms (including; Chloroplastida, Metazoa, and Rhizaria) and 13 ARGs subtypes (including; Efflux pump, Tetracycline, Multi-drug, Rifampin, Beta-lactam, Peptide, Trimethoprim) were significantly increased. While dominant metabolic pathways such as Carbohydrate, amino acid, energy and nucleotide metabolism were inhibited. This study revealed that V. spiralis has great sorption capacity for CIP than sediment and though CIP was effectively removed from the overlying water, it caused a prolonged effect on the epiphytic biofilm microbial communities.

Comparison of APTES-Functionalized Silica Fiber and Clinoptilolite for Reducing Iron Concentrations in an Acidic Iron(II) Sulfate Solution: Potential Passive Treatment Substrates

Passive treatment systems provide lower cost alternatives for remediation of mine drainage; however, acidic drainage increases treatment difficulty because of higher metal concentrations and proton competition for reactive substrates. A silica fiber functionalized with (3-aminopropyl) triethoxysilane (Si + APTES) and a naturally-occurring, microporous silicate mineral (clinoptilolite of the zeolite family) were evaluated in the laboratory as potential reactive substrates for passive treatment of mild (≥ pH of 3) acid rock drainage. Column permeability experiments with spun, 10-µm median diameter, silica fiber and loosely packed, 3.6-mm median diameter clinoptilolite indicate greater permeability and stability of clinoptilolite under flowing conditions. Batch sorption experiments with silica fiber (Si), Si + APTES, and clinoptilolite in a synthetic Fe(II)–SO4, pH 3.0 solution indicate an Fe specific sorption efficacy of Si + APTES > clinoptilolite > Si at equivalent surface areas. Specific sorption normalized to packing densities indicate greater sorption per volume for clinoptilolite. Sorption results for Si + APTES and clinoptilolite did not produce isotherms described by the Langmuir or Freundlich models, likely because of surface heterogeneity and precipitation reactions. Column sorption experiments under flowing conditions indicate an Fe removal efficacy of clinoptilolite > Si + APTES for permeable packing densities. Si + APTES demonstrated high specific sorption of Fe in batch sorption experiments and has potential use in low-flow, passive treatment of mildly acidic solutions. The balance of minimal surface preparation, greater permeability, structural stability, large surface area, micropore structure, and ion-exchange properties make clinoptilolite a better reactive substrate for passive treatment of mildly acidic solutions in high- or low-flow conditions.

Behavior of Ag species in presence of aquatic sediment minerals – In context of aquatic environmental safety

In recent years, there has been a growth in the number of products containing Ag nanoparticles (AgNPs) in many areas and their use suggests that the water-soil environment may be exposed to the contaminant with different Ag species.Therefore, the sorption of two Ag forms (i.e. Ag(I) ions and nanoparticles – AgNPs) on clay minerals (montmorillonite and kaolinite) and iron (oxyhydr)oxides (ferrihydrite) as a function of solution:mineral ratio (100:1, 250:1, 500:1), solution pH (3.0, 5.5 and 7.0) and initial Ag concentration (0.1–100 mg/dm3) was studied using batch method. In addition the binding strength/mobility of the bonded Ag species was researched. The results show a great sorption potential of clay minerals for both Ag forms and lower sorption capacity of ferrihydrite, in particular for Ag(I) ions. The maximum sorption capacities of montmorillonite, kaolinite and ferrihydrite estimated from three-parameter isotherm model of Sips were 94.39 mg/g, 117.8 mg/g and 26.48 mg/g for AgNPs and 17.92 mg/g, 21.14 mg/g and 3.072 mg/g for Ag(I) ions, respectively. Aggregation process plays an important role in sorption and mobility of AgNPs.The sequential extraction study indicated different binding mechanisms of the Ag forms onto the clay minerals and ferrihydrite, which depended on the active sites of minerals as well as the Ag species nature in the solution. Ag(I) was weakly bound by clay minerals but presence of iron (oxyhydr)oxides decreased the Ag(I) mobility and bioavailability. On the other hand, AgNPs bound with the active centers of minerals in a very strong way and were not able to release into water.The study of the binding of Ag forms by clay minerals and (oxyhydr)oxides allows to determine the influence of their physicochemical and structural properties, including e.g. pore size on Ag sorption. These results allow these properties to be taken into account in the study of environmental samples, including waters and soils.Moreover, the results showed that in the study of behavior of Ag forms in contact with the minerals, in addition to the sorption capacity, the susceptibility to their release is very important.Studies on sorption/desorption of AgNPs and Ag(I) ions as a form of oxidation of AgNPs is important for understanding the transport and fate of the Ag species in soil, sediments and surface water because of different their behavior in contact with the minerals.

Graphene-based nanomaterial for the removal of sulfamethoxazole in water

As a promising nanomaterial, graphene-oxide (GO) has shown great sorption potential for environmental contaminants. The study focusing on ability of graphene oxide as adsorbent in diminishing the concentrations of sulfamethoxazole (SMX) in synthetic wastewater. This study evaluated the ability of GO to remove SMX under different dosage of GO and different initial concentration of SMX. GO was synthesized from the oxidation of graphite flakes by using Optimized Improved Hummer’s method while the sorption study was done using the batch experiment. The result indicates that GO was able to removed up to 14.40% of SMX by optimizing the dosages of GO from 0.02 g to 0.1 g. Under different initial concentration of SMX, from 5 mg/L to 20 mg/L, the ability of GO to remove SMX is up to 5.20%. Both experimental system fit with Langmuir Isotherm Model. This indicated GO has the ability to removed SMX in higher concentration however the reaction time need to be increase. Results obtained from this work demonstrated that GO can be used as an effective adsorbents for the removal of antibiotic.

Evaluation of Commercial Humic Substances and Other Organic Amendments for the Immobilization of Copper Through 13C CPMAS NMR, FT-IR, and DSC Analyses

The application of organic amendments to contaminated agricultural lands can immobilize metals and improve soil conditions. The chemical structures and long-term stability of commercial humic substances and other composted organic amendments (sheep and horse manure, vermicompost, pine bark, and pruning waste) were analyzed using 13C CPMAS NMR, FT-IR, and DSC to evaluate their use in soil remediation. The interactions of humic substances and manure with Cu (0 and 5000 mg kg−1) at different pH (2.5 and 5.0) were studied through a batch adsorption experiment observing the changes in their molecular structure using spectroscopic techniques. Humic substances exhibited high aromaticity and phenolic and carboxylic group content, with great affinity for Cu complexation. Humic substances and pruning waste were the most stable due to their high recalcitrant organic matter contents, whereas manure was the least stable, given the labile nature of its organic matter content. There were considerable changes in the carboxylic and phenolic groups of humic substances with pH, and also with Cu, albeit in a lesser extent, especially at pH 5.0, suggesting the great sorption capacity of humic substances and the key role of pH and these functional groups in metal complexation. Manure did not exhibit such changes. Commercial humic substances could be useful amendments for the remediation of contaminated agricultural soils due to their high sorption capacities and long-term stability.

Influence of electrolyte composition and pH on glyphosate sorption by cow-dung amended soil

This study investigated the pH-dependent relationship between glyphosate and soils before (NS) and after amendment with cow-dung, CD (SACD). Sorption isotherms were generated using batch equilibration techniques from CaCl2, KCl, CaSO4 and Ca(H2PO4)2 background electrolytes. Linear partition coefficients decreased with increase in pH in the order: CaCl2>KCl > CaSO4>Ca(H2PO4)2, which reflect both the effect of the inorganic anion in terms of competition and the cation in terms of bridging interactions. However, soil amendment with CD minimized the inhibitory effect of pH increase on glyphosate sorption. Variations in glyphosate sorption from CaCl2 and Ca(H2PO4)2 were attributed to fraction of hydrophilic contribution while variations in sorption from CaCl2 and KCl were attributed to Ca-bridging and ranged from 22 to 70% across the two soils. Estimated hydrophobic partitioning () systematically decreased with increasing soil solution pH from 36 to 3% and 5 to <1% in NS and SACD, respectively. Greater sorption in NS over SACD was partly attributed to higher phosphate level in SACD which is preferentially sorbed over glyphosate. This study noted CD application as soil amendment for agriculture could impede glyphosate sorption and facilitate its off-site leaching and contamination of surface and groundwater.

Removal of Heavy Metals and Metalloids from Water Using Drinking Water Treatment Residuals as Adsorbents: A Review

Heavy metal contamination is one of the most important environmental issues. Therefore, appropriate steps need to be taken to reduce heavy metals and metalloids in water to acceptable levels. Several treatment methods have been developed recently to adsorb these pollutants. This paper reviews the ability of residuals generated as a by-product from the water treatment plants to adsorb heavy metals and metalloids from water. Water treatment residuals have great sorption capacities due to their large specific surface area and chemical composition. Sorption capacity is also affected by sorption conditions. A survey of the literature shows that water treatment residuals may be a suitable material for developing an efficient adsorbent for the removal of heavy metals and metalloids from water.