Synthesis of surface-modified porous polysulfides from soybean oil by inverse vulcanization and its sorption behavior for Pb(II), Cu(II), and Cr(III).

Guided by efficient utilization of natural plant oil and sulfur as low-cost sorbents, it is desired to tailor the porosity and composition of polysulfides to achieve their optimal applications in the management of aquatic heavy metal pollution. In this study, polysulfides derived from soybean oil and sulfur (PSSs) with improved porosity (10.2-22.9 m2/g) and surface oxygen content (3.1-7.0 wt.%) were prepared with respect to reaction time of 60 min, reaction temperature of 170 °C, and mass ratios of sulfur/soybean oil/NaCl/sodium citrate of 1:1:3:2. The sorption behaviors of PSSs under various hydrochemical conditions such as contact time, pH, ionic strength, coexisting cations and anions, temperature were systematically investigated. PSSs presented a fast sorption kinetic (5.0 h) and obviously improved maximum sorption capacities for Pb(II) (180.5 mg/g), Cu(II) (49.4 mg/g), and Cr(III) (37.0 mg/g) at pH 5.0 and T 298 K, in comparison with polymers made without NaCl/sodium citrate. This study provided a valuable reference for the facile preparation of functional polysulfides as well as a meaningful option for the removal of aquatic heavy metals.

Eco-friendly nanoparticles: mechanisms and capacities for efficient removal of heavy metals and phosphate from water using definitive screening design approach.

Can nano-zero-valent iron, synthesized using oak leaf extract, be the key solution for water preservation, efficiently removing heavy metal ions and phosphate anions simultaneously? This research unveils how this technology not only promises high efficiency in the remediation of water resources, but also sets new standards for environmentally friendly processes. The high antioxidant capacity and high phenol content indicate suggest the possibility of oak-nZVI synthesis using oak leaf extract as a stable material with minimal agglomeration. The simultaneous removal of Cd and phosphates, as well as and Ni and phosphates was optimized by a statistically designed experiment with a definitive screening design approach. By defining the key factors with the most significant impact, a more efficient and faster method is achieved, improving the economic sustainability of the research by minimizing the number of experiments while maximizing precision. In terms of significance, four input parameters affecting process productivity were monitored: initial metal concentration (1-9 mg L-1), initial ion concentration (1-9 mg L-1), pH value (2-10), and oak-nZVI dosage (2-16 mL). The process optimization resulted in the highest simultaneous removal efficiency of 98.99 and 87.30% for cadmium and phosphate ions, respectively. The highest efficiency for the simultaneous removal of nickel and phosphate ions was 93.44 and 96.75%, respectively. The optimization process fits within the confidence intervals, which confirms the assumption that the selected regression model well describes the process. In the context of e of the challenges and problems of environmental protection, this work has shown considerable potential and successful application for the simultaneous removal of Cd(II) and Ni(II) in the presence of phosphates from water.

Attempts to obtain clean biochar from hyperaccumulator through pyrolysis: Removal of heavy metals and transformation of phosphorus.

The sound disposal of the ensuing heavy metal-rich plants can address the aftermath of phytoremediation. In this study, the first attempt was made to obtain heavy metals-free and phosphorus-rich biochar from phytoremediation residue (PR) by pyrolysis, and the effects of chlorinating agent type, chlorine dosage, and pyrolysis residence time on heavy metal removal, phosphorus (P) transformation, and biochar properties were investigated. The results showed that as chlorine dosage and pyrolysis residence time increased, added polyvinyl chloride (PVC) reduced the concentration of Zn in biochar to one-tenth of that in PR by intensified chlorination, where both Zn concentration (2727.50 mg/kg) and its leaching concentration (29.13 mg/L) met the utilization requirements, in which the acid-base property of biochar plays a key role in heavy metal leaching. Meanwhile, more than 90% of P in PR remained in biochar and the bioavailability of P in biochar enhanced with the decomposition of organic P to inorganic P, where the concentration of plant-availability P (Pnac) expanded from 1878.40 mg/kg in PR to 8454.00 mg/kg in biochar. This study demonstrated that heavy metal hyperaccumulator can be converted into heavy metal-free and phosphorus-rich biochar with promising applications, which provides new perspectives for the treatment of such hazardous wastes.

Inverse vulcanization induced oxygen modified porous polysulfides for efficient sorption of heavy metals.

The applications of polysulfides derived from natural plant oil and sulfur via the inverse vulcanization in the removal of heavy metals from aqueous solutions suffered from their low porosity and scarce surface functionality because of their hydrophobic surfaces and bulk characteristics. In this study, polysulfides from sulfur and palm oil (PSPs) with significantly enhanced porosity (13.7-24.1 m2/g) and surface oxygen-containing functional groups (6.9-8.6 wt.%) were synthesized with the optimization of process conditions including reaction time, temperature, and mass ratios of sulfur/palm oil/NaCl/sodium citrate. PSPs were applied as sorbents to remove heavy metals present in aqueous solutions. The integration of porosity and oxygen modification allowed a fast kinetic (4.0 h) and enhanced maximum sorption capacities for Pb(II) (218.5 mg/g), Cu(II) (74.8 mg/g), and Cr(III) (68.4 mg/g) at pH 5.0 and T 298 K comparing with polysulfides made without NaCl/sodium citrate. The sorption behaviors of Pb(II), Cu(II), and Cr(III) on PSPs were highly dependent on the solution pH values and ionic strength. The sorption presented excellent anti-interference capability for the coexisting cations and anions. The sorption processes were endothermic and spontaneous. This work would guide the preparation of porous polysulfides with surface modification as efficient sorbents to remediate heavy metals from aqueous solutions.

Novel surface-treatment for bottom ash from municipal solid waste incineration to reduce the heavy metals leachability for a sustainable environment.

Unconventional treatments can provide a modification to convert ash waste into valuable materials that can be used in various applications. This study focuses on bottom ash (BA) collected from a local incineration plant and characterizes its chemical composition before and after pretreatment by coating with polymers. The toxicity-characteristic leaching procedure (TCLP) was used to identify selected heavy metal leaching after treatment with vinyl-terminated polydimethylsiloxane (PDMS) of different molecular weights. BA coatings were incorporated in two ratios, 0.5% and 1%, by milling to avoid heavy metal leaching. The results showed that all the coating batches had reduced concentrations of copper (Cu), manganese (Mn), and zinc (Zn), whereas the concentrations of chromium (Cr) and cadmium (Cd) showed higher amounts of BAV34 (0.5%) and BAV25 (1%). The treated BA with GP demonstrated percentages of reduction of 70%, 65%, 80%, 75%, 90%, and 80% for Cu, Mn, Ni, Zn, Pb, and Cd, respectively. The milling procedure reduced the particle size of the coated ash. Hydrophobicity was observed in all coating batches compared to untreated BA. The thermogravimetric analysis (TGA) results showed variations between BA and treated BA, which confirmed that PDMS caused surface modification. These features have potential significance for extending the use of coated ash as a sustainable material for construction applications.

Simultaneous removal of phosphorus, zinc, and lead from oligotrophic ecosystem by iron-driven denitrification: Performance and mechanisms.

Based on the current situation of complex pollution caused in surface water by oligotrophic condition and heavy metal release from river and lake bottom sediments. This study aimed to achieve the simultaneous removal of nitrate, phosphorus, Zn2+ and Pb2+ through microbial approach. At nitrate concentration of 4.82 mg L-1, carbon to nitrogen ratio of 1.5, pH of 6.0, and Fe2+ concentration of 5.0 mg L-1, the nitrate removal efficiency of Zoogloea sp. FY-6 reached 95.17%. The addition of pollutants under these conditions resulted in 88.76% removal of total phosphorus at 18 h, and 85.46 and 78.59% removal of Zn2+ and Pb2+ respectively, and there was competition for adsorption between Zn2+ and Pb2+. Extracellular polymers and fluorescence excitation-emission substrates confirmed that Fe2+ reduced heavy metal toxicity through promoting bacterial production of secretions and promotes denitrification as a carbon source. Meanwhile, contaminant removal curves and Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy demonstrated the synchronous removal of Zn2+ and Pb2+ mainly through biological action and the formation of nanoscale iron oxides. Biological-iron precipitation also provided adsorption sites for phosphorus. This research provides the theoretical foundation for applying microorganisms to restore oligotrophic source water (rivers and lakes) containing complex pollutants.

Preparation and characterization of ZSM-5 molecular sieve using coal gangue as a raw material via solvent-free method: Adsorption performance tests for heavy metal ions and methylene blue.

Coal gangue is a kind of solid waste produced in the process of coal mining and washing. Its silicon aluminum silicon aluminum oxide content is high, respectively, which are suitable for resource utilization as raw materials for Si-Al molecular sieving. In this paper, a novel, simple, low-cost, and environmentally friendly process was carried out to prepare ZSM-5 zeolite by solvent free method after calcination, acid leaching, and alkali melting. The obtained samples were characterized by Energy Dispersive Spectrometer (EDS), Inductively Coupled Plasma (ICP), Thermo-gravimetry Analysis (TG), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectrometer (FTIR) X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and N2 adsorption isotherm. The characteristics of the raw materials and the adsorption mechanism of the prepared samples were characterized. Through a series of pretreatment such as calcined acid leaching and alkali melting of the raw materials, the silicon-aluminum ratio of the sample reaches 1.749, and the maximum specific surface area of the sample can reach 252.59 m2/g. The obtained samples were used to adsorb heavy metal ions and methylene blue solution, and the removal rate of lead ions and methylene blue solution was more than 95%. The theoretical maximum adsorption capacity of Pb ion, methylene blue solution and copper ion can reach 232.56 mg/g and 118.34 mg/g. The adsorption process is mainly chemical adsorption. The product could be suitable for removing both heavy metal ions and cationic dyes from the wastewater and had broad application prospects.

Phosphorus recovery from sewage sludge ash (SSA): An integrated technical, environmental and economic assessment of wet-chemical and thermochemical methods.

Incineration is a promising disposal method for sewage sludge (SS), enriching more than 90% of phosphorus (P) in the influent into the powdered product, sewage sludge ash (SSA), which is convenient for further P recovery. Due to insufficient bioavailable P and enriched heavy metals (HMs) in SSA, it is limited to be used directly as fertilizer. Hence, this paper provides an overview of P transformation in SS incineration, characterization of SSA components, and wet-chemical and thermochemical processes for P recovery with a comprehensive technical, economic, and environmental assessment. P extraction and purification is an important technical step to achieve P recovery from SSA, where the key to all technologies is how to achieve efficient separation of P and HMs at a low economic and environmental cost. It can be clear seen from the review that the economics of P recovery from SSA are often weak due to many factors. For example, the cost of wet-chemical methods is approximately 5∼6 €/kg P, while the cost of recovering P by thermochemical methods is about 2∼3 €/kg P, which is slightly higher than the current P fertilizer (1 €/kg P). So, for now, legislation is significant for promoting P recovery from SSA. In this regard, the relevant experience in Europe is worth learning from countries that have not yet carried out P recovery from SSA, and to develop appropriate policies and legislation according to their own national conditions.

A circular economy approach to drinking water treatment residue management in a catchment impacted by historic metal mines.

Drinking water treatment residues (DWTR) from mining areas which remove and contain potentially toxic elements (PTE) could still potentially be used as a soil amendment to restore contaminated sites in the same catchment, thus eliminating waste and reducing the chemical and physical mobility of the pollutants. To assess this restorative and regenerative approach to DWTR management, field and pot trials were established with soils from a historic Pb-Zn mine site in the North East of England, amended with either local DWTR or the nearest available municipal green waste compost (GWC). Soils from the mine site were found to have very low levels of nutrients and very high levels of PTE (Pb and Zn > 13, 000 mg/kg). The perennial grass species Phalaris arundinacea, known for many ecosystem service benefits including soil stabilization, was used throughout this study. The application of the BCR sequential extraction to soils amended with the DWTR in the pot trials found a significant decrease in the bioavailability of Pb and Cu (p < 0.05) after plant growth when compared with an unamended control. The field trial involved 648 pre-grown grass plants planted-out into mine soils amended with either DWTR, GWC or a mixture (MIX) of the two, all at rates of 25-30% w/w. Both amendments and the MIX had significant positive effects on biomass production compared to the unamended control in the following order GWC > MIX > DWTR (p < 0.05). Results of the elemental analysis of biomass from the field trial were generally ambiguous and did not reflect the decreased bioavailability noted in the pot trials using the BCR procedure. Pot trials, however, showed increases in plant growth and decreases in concentrations of Cr, Cu, Pb and Zn in above ground biomass following the application of both amendments. Further work should involve the testing of a mixture of DWTR and other soil amendments to enhance plant growth. The success of these trials should provide confidence for those working in drinking water treatment and catchment management to reuse the waste residues in a circular economy and a sustainable way that could improve water quality over time.

Hydrothermal carbonization combined with thermochemical treatment of sewage sludge: Effects of MgCl2 on the migration of phosphorus and heavy metal.

Phosphorus (P) is a non-regenerative and finite raw material. Due to its decreasing availability, and to protect the environment, recycling methods are needed. With the focus on closing nutrient cycles, sewage sludge (SS) is a potential source for P recovery. The objective of this study was to produce a mineral P-reach fertilizer. For this purpose, the treatment of SS in a multi-stage process, consisting of a hydrothermal carbonization (HTC) and thermochemical post-treatment was examined and compared with a direct thermochemical treatment. The focus was on the transformation of P and the migration of the heavy metals during the processes. In addition, the role of MgCl2 as an additive was examined. During the HTC, most of the P remained in the HTC-char, so that the P content increased in the HTC-char compared with the SS. The addition of MgCl2 to the process resulted in lower transportation rates of P in the liquid phase and higher P solubilities in water, citric acid, and alkalic ammonium citrate out of the solid phase. The thermochemical treatment of SS and the HTC-chars further concentrated P in the ash. Retention rates of >97% were achieved, and P2O5 contents in the ash were as high as ∼16 wt-%. The presence of the additive resulted in (i) higher retention rates of P in the ashes (ii) higher P-solubility and (iii) higher removal rates of easily volatile heavy metals such as Pb and Zn, and the treatment of HTC-char favored these effects compared with the direct treatment of SS.

Biosynthesis and Mathematical Interpretation of Zero-Valent Iron NPs Using Nigella sativa Seed Tincture for Indemnification of Carcinogenic Metals Present in Industrial Effluents.

Zero-valent iron nanoparticles (ZVI-NPs) are utilized for the indemnification of a wide range of environmental pollutants. Among the pollutants, heavy metal contamination is the major environmental concern due to their increasing prevalence and durability. In this study, heavy metal remediation capabilities are determined by the green synthesis of ZVI-NPs using aqueous seed extract of Nigella sativa which is a convenient, environmentally friendly, efficient, and cost-effective technique. The seed extract of Nigella sativa was utilized as a capping and reducing agent for the generation of ZVI-NPs. UV-visible spectrophotometry (UV-vis), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), and Fourier transform infrared spectroscopy (FTIR) was used to investigate the ZVI-NP composition, shape, elemental constitution, and perspective functional groups, respectively. The biosynthesized ZVI-NPs displayed a peak of plasmon resonance spectra at 340 nm. The synthesized NPs were cylindrical in shape, with a size of 2 nm and (-OH) hydroxyl, (C-H) alkanes and alkynes N-C, N=C, C-O, =CH functional groups attached to the surface of ZVI-NPs. Heavy metals were successfully remediated from industrial wastewater collected from the various tanneries of Kasur. During the reaction duration of 24 h, different concentrations of ZVI-NPs (10 µg, 20 µg and 30 µg) per 100 mL were utilized for the removal of heavy metals from industrial wastewater. The 30 µg/100 mL of ZVI-NPs proved the pre-eminent concentration of NPs as it removed >90% of heavy metals. The synthesized ZVI-NPs were analyzed for compatibility with the biological system resulting in 87.7% free radical scavenging, 96.16% inhibition of protein denaturation, 60.29% and 46.13% anti-cancerism against U87-MG and HEK 293 cell lines, respectively. The physiochemical and exposure mathematical models of ZVI-NPs represented them as stable and ecofriendly NPs. It proved that biologically synthesized NPs from a seed tincture of Nigella sativa have a strong potential to indemnify heavy metals found in industrial effluent samples.

A new basic burning raw material for simultaneous stabilization/solidification of PO43--P and F- in phosphogypsum.

Phosphogypsum (PG) contains a lot of soluble phosphate (PO43--P) and fluorine ion (F-), which seriously has hindered the sustainable development of the phosphorous chemical industry. In this study, a new burning raw material (BRM) as an intermediate product in the cement production process was used for PO43--P and F- stabilize in PG. The stabilizing mechanism of PO43--P and F- were investigated by Fourier Transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD), Scanning Electron Microscopy (SEM), X-ray fluorescence (XRF) and X-ray spectroscopy system (XPS). The effect of PG and BRM weight ratio, solid-to-liquid ratio, reaction time, and reaction temperature on the concentrations of PO43--P and F- were studied. The results showed that the concentration of F- in the PG leaching solution was 8.65 mg/L and the stabilizing efficiency of PO43--P was 99.78%, as well as the pH of the PG leaching solution was 8.12 when the weight ratio of PG and BRM was 100:2, and the solid to liquid ratio was 4:1, reacting for 24 h at the temperature of 30 â„ƒ. PO43--P and F- were mostly solidified as Ca5(PO4)3F, CaPO3(OH), Ca5(PO4)3(OH), Ca2P2O7·2H2O, CaSO4PO3(OH)·4H2O, CaF2, and CaFPO3·2H2O. Leaching test results indicated that the concentrations of PO43--P, F- and heavy metals were less than the integrated wastewater discharge standard (GB8978-1996). This study provides a new harmless treatment method for PG.

Assessment of heavy metals and macromineral in frequently used medicinal plants from Algerian Sahara traditional ethnopharmacopeia.

In this study, a total of 15 elements, both physiological and causing toxic effects, have been determined in 9 medicinal plants collected from their natural environment in the Algerian Sahara regions. The concentrations of elements were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) after acid digestion and by the X-ray fluorescence spectrometry (XRF). By analyzing the spiked test and the reference materials, the accuracy of the measurements was determined. Our findings show differences in elements composition and concentration between the species under investigation, indicating differences in physiological function of the plant as a result of elemental interactions within it. The elements were quantified (in µg/g): Br (0.04-5.44), Cd (1.21-1.34), Co (1.12-64.35), Cr (1.51-59.05), Cu (1.81-9.28), Fe (94.26-668.55), Mn (16.34-70.77), Ni (1.5-53.64), Pb (1.18-2.55), Zn (1.21-310.80) and (in mg/g): Ca (4.23-4.70), Cl (21.98-117.91), P (28.92-30.49), S (4.15-11.95), Si (1.99-2.36). Mean element levels in medicinal plants were established in decreasing order as follows: Zn>Mn>Cu>Cr>Ni>Pb>Cd>Co. Except for nickel, which reached 53.64µg/g in the Capparis spinosa L species, heavy metal concentrations were found to be low in all samples. Based on traditional use, we can cautiously conclude that these medicinal plants pose no risk to users.

Modified biochar/humic substance/fertiliser compound soil conditioner for highly efficient improvement of soil fertility and heavy metals remediation in acidic soils.

Fertile and uncontaminated soil with appropriate pH is crucial in terms of the agricultural sustainable development. Herein, a compound soil conditioner containing chitosan modified straw biochar (CBC), kitchen waste compost product-derived humic substance (HS), NPK compound fertiliser (NPK-CF) was prepared to simultaneously adjust acidic soil pH, improve fertility, and immobilize heavy metal. The results exhibited that the best Pb and NH4+ adsorption performance was obtained in CBC with chitosan:biochar of 1:5. Then, the acid soil pH was improved from 5.03 to 6.66 in the presence of CBC/HS (5:5) with 3% addition weight (the mass ratio of conditioner to soil). Meanwhile, compared with the control, the contents of organic matter, available nitrogen, and available phosphorus significantly increased by 52.4%, 92.6%, and 136.3%, respectively. Moreover, Pb was highly efficient immobilised by CBC, and the concentration of Pb in the soil was decreased by 55.2%. The optimal growth trend of ryegrass was obtained in the presence of 3% addition weight (the mass ratio of conditioner to soil) CBC/HS (CBC:HS = 5:5) combined with 60% of the recommended NPK-CF application weight, which was mainly contributed by the improvement of the soil microbial abundance and community structure diversity. The addition of CBC/HS could effectively reduce the addition of NPK-CF and contribute to simultaneous controlling nitrogen loss, releasing phosphorus, immobilising Pb, adjusting pH, improving soil quality and controlling nonpoint pollution.

Phytochemical composition, cytotoxicity, antioxidant and antimicrobial responses of Lavandula dentata L. grown under different levels of heavy metals stress condition.

In order to know if the heavy metals stress condition is boon or bane for the plants growth, Lavandula dentata species was planted in pots under different levels of heavy metals stress condition and the phytochemical composition, cytotoxicity, antioxidant and antimicrobial responses of their leaf ethanolic extracts toward this stress condition were investigated compared to the control samples. Our findings showed significant differences in heavy metals bioaccumulation, photosynthetic pigments and total phenolic/flavonoids contents among L. dentata leafs ethanolic extracts, grown under different levels of heavy metals stress condition. The L. dentata leafs extracts, grown under Zn and Cu stress condition, showed the highest antioxidant and antimicrobial activities than those grown under Cd and Pb stress condition. Comparatively, the L. dentata leafs extracts, grown under Zn stress condition, showed higher antioxidant activity, and those, grown under Cu stress condition, showed higher antimicrobial activity. The highest cytotoxicity was showed by L. dentata leaf extracts, grown under Cd and Pb stress condition, which lead to conclude that these extracts could be served as a novel scaffold in search for new drugs against cancer. In conclusion, the highlighted variability reflects the high impact of heavy metals stress condition on phytochemical composition and consequently on the biological activities of medicinal plants. Such impact led to conclude that we should select medicinal plants extracts to be investigated carefully depending on this stress condition, in order to isolate the bioactive components or to have the best quality of extracts in terms of biological activities.

Remediation of copper and lead contaminated sediments using iron-based granule biochar: mechanisms and enzyme activity.

In recent years, there has been a growing concern about heavy metal contamination in sediments. In this study, iron-based granular biochar (MGB) is prepared to remediate Cu and Pb contaminated sediments. Characterizations via scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) show that the rough surface of MGB with abundant pore structures and a large number of oxygen-containing functional groups that facilitate stabilization of Cu and Pb in sediments. Potential mobility and bioavailability of Cu and Pb are investigated using BCR sequential extraction in the 35 day remediation experiment. The XPS results indicate that FeOOH and C-OH play a crucial part in stabilizing heavy metals. Large affinity of FeOOH for Pb allows it to occupy a proportion in F2 while C-OH is attractive to Cu. Changes of pH, organic matter (OM), and available phosphorus (AP) in sediments after adding MGB as well as the relationship between changes and the stable solidification of Cu and Pb are explored. The stable solidification of heavy metals effectively reduces the available phosphorus in sediments. Magnetic and particle properties of the material are used to reduce the impact of MGB aging on sediment environment and separate it from the remediated sediment. Finally, 3% of MGB significantly enhanced the sediment catalase activity in the biological enzyme activity experiment. All findings indicate that MGB is a green and environmentally friendly sediment remediation material with satisfactory potential in synergistically stabilizing heavy metals and phosphorus.Highlights The complexation of FeOOH with Pb on the surface of MGB fixes it to the reduced stateThe C-OH on the surface of MGB is more attractive to Cu than PbMGB effectively mitigates the release of bioavailable phosphorus from sediments to overlying water.

Co-pyrolysis of biomass and phosphate tailing to produce potential phosphorus-rich biochar: efficient removal of heavy metals and the underlying mechanisms.

Application of biochar to treat heavy metal polluted wastewater has received increasing attention; however, the immobilization ability of pristine biochar for metal ions is still limited. In this study, phosphate tailing was co-pyrolyzed with sawdust and peanut shell to acquire phosphorus-rich biochars with high removal rates for Cd, Zn, Pb, and Cu. Meanwhile, the improvement mechanisms by phosphate tailing were clarified by XRD, FTIR, SEM-EDS, BET-N2, and model fitting. Results showed that after phosphate tailing impregnation, surface area of sawdust, and peanut shell biochars increased from to 11.6 m2 g-1, and from 43.5 to 53.4 m2 g-1, respectively. Functional groups of -COOH and CO32- on biochar increased and the P2O74- newly generated. Besides, large amounts of Ca(PO3)2 and Ca2P2O7 crystals were detected in biochar ash. As for sawdust biochar, loading of phosphate tailing raised the sorption rates of Cd, Zn, Pb, and Cu by 0.35, 0.61, 1.10, and 2.64 times, respectively, as for peanut shell biochar, it was raised by 0.12, 0.47, 0.11, and 1.98 times, respectively. The sorption isotherms by phosphate tailing-loaded biochars were better fitted to Langmuir (R2 = 0.85-1.00) than Freundlich model (R2 = 0.58-0.91). Heavy metals could bind with -OH and -COOH on phosphate tailing-loaded biochars, meanwhile generated phosphorus-rich precipitation with PO3- and P2O74+, including Cd2P2O7, Cd(PO3)2, Zn (PO3)2, Pb (PO3)2, Pb2P2O7, Cu(PO3)2, and Cu2P2O7. This study proposed an innovative method to produce phosphorus-rich biochars by loading phosphate tailing for highly efficient removal of heavy metals from water bodies, and also realized the resource utilization of phosphate tailing, which was of great significance to reduce environmental pollution.

[Adsorption of Phosphate and Heavy Metals by Lanthanum Modified Zeolite and Its Performance in Sediment Inactivation].

Due to the large scale of mining and smelting activities, considerable amounts of heavy metals are discharged into the environment and accumulate in the sediment of rivers and lakes. The combined pollution of heavy metals and the intrinsic phosphorus in sediment calls for novel remediation technologies. In this study, lanthanum-modified zeolite (LMZ) was employed as an inactivation agent for the immobilization of phosphorus, zinc, and lead in sediments. The adsorption capacities as well as the inactivation performance of LMZ for P, Zn, and Pb were investigated, and the adsorption mechanisms were explored via desorption experiments, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The results indicated that the adsorption maximums of LMZ for P, Zn, and Pb were 53.76, 27.70, and 123.45 mg·g-1, respectively. Pre-adsorption of Zn and Pb had a negligible effect on the P adsorption by LMZ, whereas the adsorption of Zn and Pb were inhibited significantly by the pre-adsorption. P, Zn, and Pb in the sediment were transformed to more stable or less bioavailable forms by dosing 0.83% and 1.66% weight percentages of LMZ. It was found that P, Zn, and Pb were adsorbed through the formation of inner-sphere complexes. Further, desorption experiments and XRD patterns suggested that electrostatic attraction and surface precipitation also contributed to the adsorption of Zn and Pb, respectively.

Basic principles and problems in decontamination of natural disperse systems. The electrokinetic treatment of soils.

The main chemical, biological and physical methods of deactivation of such natural disperse systems as soils and bottom sediments from charged and uncharged pollutants are analyzed. The impact of properties of natural disperse systems and the substances causing their contamination on the expediency of using some specific detoxication method is considered. The peculiarities of ex-situ and in-situ treatment are indicated. It is shown that in many cases the use of such well-known methods as washing, flushing, solidification/stabilization, thermal processing, steam extraction, and others is effective and rational. Advantages and disadvantages of considered methods are presented. Much attention is devoted to the fine disperse systems with low aerodynamic and hydrodynamic permeations, which are most complicated from the viewpoint of decontamination and best suited for the use of the electrokinetic decontamination method. Electrokinetic treatment demonstrates an optimal compromise between the degree of decontamination and energy consumption in comparison with other methods, for example, thermal processing. The performance efficiency by using this method is studied depending on such characteristics of dispersions subjected to decontamination as the initial soil pH value, its exchange capacity and buffer capacity. It has been shown that one of the ecologically acceptable ways to accelerate and enhance electrokinetic remediation is the electrohydrodynamic pH control by selecting the pumping rate of neutral electrolytes in electrode chambers. Examples of applying this method for remediation of different types of soil from heavy metals and hydrophobic organic compounds are presented.

Characteristic pollutant purification analysis of modified phosphogypsum comprehensive utilization.

The waste product phosphogypsum (PG) is produced in phosphoric acid production processes. Its storage requires large amounts of land resources and poses serious environmental risks. In this work, detailed experimental research was carried out to investigate the potential reuse of PG after calcination modification as a novel building material for cast-in-place concrete products. The calcination modification mechanism was studied, and the environmental risk assessment of modified PG was presented. The results showed that the calcination modification includes crystal phase transformation, removal of impurities, and modifying the pH value. The calcination was carried out at 280 °C for 5 h, where the resulting product was a pH value of 7.1, and the soluble fluorine and phosphorus removal rates reached up to 69.2% and 71.2%, respectively. These removal rates met the requirements of the China national standard Phosphogypsum (GB/T 23456-2018). To ensure the environmental safety, ecological risk assessment methods for determining the leaching toxicity of the modified PG were employed. The toxicity of Ba and P elements in the modified PG products was assessed, as well as the leaching toxicity concentrations of all particular heavy metals, which were found well below the limits set by the national standards. All the results presented strongly suggest that the 280 °C modified PG presented here has excellent application potential as a raw component in building materials.