Adsorbent For Water Purification Research Articles

Structural insights into amino-modified defective UiO-67: Enhancing phosphate adsorption through multiple active sites synergistic interactions

Zirconium-based Metal-Organic Frameworks (Zr-MOFs) have attracted significant attention for phosphate removal due to their large specific surface area and abundant active sites. In this study, amino-modified Zr-MOFs were synthesized and used for phosphate removal, with a focus on investigating the relationship between the physicochemical structure of the amino-modified Zr-MOFs and phosphate adsorption, as well as the role of the amino groups. A series of amino-modified Zr-MOFs (UiO-67) were synthesized and characterized, with particular emphasis on the variant with one amino group functionalization on a defect-rich framework, designated as DUN. The results reveal that amino modification of defective UiO-67 (DUN) increases the number of phosphate adsorption sites per unit mass and specific surface area, thereby enhancing phosphate adsorption capacity, which is significantly higher than that of other synthesized UiO-67 variants. The role of amino group not only enhances the affinity for phosphate and the adsorption efficiency at low phosphate concentrations but also accelerates the phosphate adsorption rate. Through comprehensive characterization and DFT simulations, the superior performance of DUN is primarily attributed to the synergistic effects of its structural defects, carboxyl groups, and introduced amino functionalities. The defects at Zr nodes in DUN contribute significantly to phosphate adsorption by providing Zr-OH groups and oxygen vacancies. Concurrently, the carboxyl groups present in the DUN's ligand linkers engage in hydrogen bonding interactions with phosphate. The amino groups, a novel addition to the DUN structure, not only provide additional adsorption sites but also significantly enhance the strength of the existing hydrogen bonds and the Zr-O-P coordination interactions. This study sheds light on the intricate relationship between the physicochemical structure of Zr-MOFs and their phosphate adsorption capacity, providing a theoretical basis and practical approach for developing efficient Zr-MOF-based adsorbents for water purification.

Low Cost Water Purification: Harnessing Adsorbents for Sustainable Treatment Solutions

Water is essential for life, yet millions lack access to clean drinking water. Low-cost treatment methods are crucial to ensure equitable access to safe water and prevent waterborne diseases in underserved communities. The study devised a 12-liter water filter utilizing pebbles, sand, and adsorbents biochar of Julifora, cashew nut shell and rice husk. Results demonstrated the filter's effectiveness in sustaining pH levels while reducing chloride, fluoride, hardness and alkalinity. Particularly noteworthy was the capacity of cashew nut biochar to efficiently adsorb chloride, fluoride, hardness and alkalinity as 27%, 37%, 38% and 43% respectively. This indicates its promising role as an adsorbent for water purification. The findings underscore the potential of the designed filter in improving drinking water quality by mitigating contaminants. Further refinement and optimization of the filter could enhance its efficacy in meeting stringent water quality standards, addressing the pressing need for accessible and safe drinking water globally.

On the diverse utility of Cu doped ZnS/Fe3O4 nanocomposites.

The global water crisis is a growing concern, with water pollution from organic dyes being a significant issue. Photocatalysis has emerged as a sustainable and renewable method for removing organic pollutants from wastewater. The study synthesized innovative (2.5, 5 and 10 wt%) Cu doped zinc sulfide/iron oxide nanocomposites using a sonochemical method, which have versatile applications in adsorption and photocatalytic degradation of organic pollutants in wastewater. The nanocomposites underwent comprehensive characterization using powder X-ray diffraction, fourier-transform infrared spectroscopy, photoluminescence spectroscopy, Ultraviolet-Visible spectrophotometer, field emission scanning electron microscopy combined with energy dispersive X-ray spectroscopy and Mott-Schottky analysis. The synthesized samples demonstrate strong adsorption ability to remove RhB and MB dyes. Afterward, we evaluated their capability to degrade Rhodamine B (RhB) dye under UV light exposure. The greatest photocatalytic efficiency was noticed when employing a UV-C lamp in combination with the 10 wt% Cu doped ZnS/Fe3O4 nanocomposite as photocatalyst (98.8% degradation after 60 min irradiation). The Langmuir-Hinshelwood model can be used to describe the pseudo first order kinetics of RhB dye photodegradation. The calculated ban gap values are 4.77, 4.67, and 4.55 eV, for (2.5, 5 and 10 wt%) Cu doped ZnS/Fe3O4, respectively. Furthermore, 10 wt% Cu doped ZnS/Fe3O4 showed good recyclability, with a degradation rate of 89% even after five cycles. Consequently, prepared samples have outstanding photocatalytic activity and can be used as useful adsorbents in water purification.

Functionalized activated carbon with whey protein amyloid fibrils for adsorption of arsenic from water

Globally, more than 200 million people are exposed to elevated concentrations of arsenic in groundwater, thus representing an important environmental and public health problem. Apart from inorganic species, water quality suffers also from the occurrence of organic pollutants discharged by the food sector like whey, a by-product of the dairy industry. The valorisation of these organic residues is relevant to reduce water pollution and to develop new materials for different applications. This research reports the synthesis and evaluation of a novel adsorptive activated carbon composite modified with whey protein amyloids for arsenic removal from water. The adsorbent was characterized with FT-IR spectroscopy, X-ray diffraction, N2 physisorption, pH at point of zero charge determination, and thermogravimetric analysis. Experimental adsorption kinetics and isotherms of arsenic removal were determined at optimal pH 5.0, best fitted with the PSO and Sips model, respectively. The corresponding maximum adsorption capacity for As5+ was 0.16 mmol g−1 through an endothermic process. Surface complexation was the predominant phenomenon in the adsorption mechanism as the As-O bond was formed via whey’s functional groups, hydroxyl, amine, and amide, with the latter having the strong affinity to arsenate as elucidated by the HSAB theory. This study highlights the potential of whey protein as a raw material to produce added-value products and its performance as a precursor of novel adsorbents for water purification, therefore minimizing their associated disposal cost and addressing relevant environmental concerns such as arsenic contamination.

Recent advances of copolymer for water treatment.

Increasing water pollution due to anthropogenic activities prompts the quest for an effective water treatment method. Polymeric materials have gained attention as adsorbents for water purification. Membranes are majorly made from homopolymeric materials. However, recent studies have focused on using copolymeric materials for improved performance. In this review, the basics of copolymerization including various types of copolymers, synthetic approaches, and their applications in various water pollutants removal are discussed in detail. Advances in water treatment technology using copolymeric materials as adsorbent/membranes in the last 4 years are covered with insights into the future outlook and areas of improvement in terms of copolymer composites for water treatment. Studies from the literature did not only reveal effectiveness of copolymer as a flocculant/antifouling materials and in removal of selective toxic metals, oil, and microbes but also demonstrated recyclability of the copolymer sorbents/membrane. Full exploration of unique copolymer textural and structural properties could lead to great advancement in water treatment process. PRACTITIONER POINTS: The copolymer types and synthetic methods are discussed. Application of copolymer as adsorbent/membranes for water treatment is presented. Recent advances show good pollutants removal for toxic metals, oil, and organics. Copolymer composites have great potential as adsorbent/membranes for future use in water treatment processes.

АДСОРБЦИЯ ИОНОВ ЖЕЛЕЗА (III) ИЗ ИХ ВОДНЫХ РАСТВОРОВ С ПОМОЩЬЮ КИСЛОТНОАКТИВИРОВАННОЙ ГЛИНЫ МЕСТОРОЖДЕНИЯ "ПОДГОРНОЕ - 3"

Water is an essential resource used by all organisms on earth. Recently, however, contamination of water by heavy metal ions, such as Fe(III), from human activities has become more common. In addition to deterioration of colour, odour and taste, consumption of such water has a negative impact on public health: liver, pancreas, heart diseases develop, and metabolism is disturbed. For this reason, purification of water from Fe (III) ions is an urgent task, which is solved, among other things, by sorbing it from aqueous media with bentonite-like clays and derivatives based on them. Earlier we studied the material (chemical, mineralogical) composition of bentonite-like clay of Podgornoye-3 site of Nikolskoye deposit of Voronezh region and gave a favourable assessment for the use of this clay as an adsorbent for water purification. This paper presents the results of the study of Fe (III) adsorption from aqueous solutions by three different products obtained by acid treatment of bentonite-like clay. The influence of various factors (duration of adsorption, pH of the medium in which the process took place, initial concentrations of adsorbent and sorbate, concentration of sulphuric acid with which the clay was treated) on the adsorption efficiency was studied in the experiments. It was determined by estimating the absolute adsorption i.e. the ratio of adsorbed Fe (III) to the mass of adsorbent and as relative i.e. the ratio of adsorbed Fe (III) to the initial amount of Fe (III) in per cent. It was found that adsorption efficiency increases with increase in contact duration, increase in pH (between 1.5 and 4), increase in adsorbent:sorbate ratio.

Recent development in the formation and surface modification of cellulose-bead nanocomposites as adsorbents for water purification: a comprehensive review

Abstract Water pollution is an issue of global concern that demands effective and sustainable solutions through water purification. Adsorption is a popular method for water treatment because it is inexpensive and has a high performance rate. Although commercial activated carbon is the generally preferred adsorbent for adsorption, its widespread use is affected by the high cost and challenges encountered during column adsorption. Biopolymers like cellulose and its derivatives have the potential to replace expensive adsorbents due to their unique characteristics. In recent years, cellulose-bead nanocomposites have gained significant attention as promising adsorbents due to their ability to circumvent the challenges encountered when using powdered adsorbents. To fabricate cellulose beads, cellulose fiber is separated from its source, dissolved in appropriate solvents, shaped into spherical particles and subsequently modified (via esterification, oxidation, crosslinking agents, etc.) to improve its adsorption capacity. This comprehensive review paper presents a detailed analysis of the recent development in the formation and surface modification of 3-D structured cellulose nanocomposites. The outcome of this review on modified cellulose-bead demonstrates their successful fabrication and high adsorption capacities for different contaminants. It is anticipated that cellulose beads, as a bio-adsorbent in industrial settings, will be a low-cost alternative to the more expensive adsorbents shortly.

The Development of Alginate/Ag NPs/Caffeic Acid Composite Membranes as Adsorbents for Water Purification

Since the water pollution problem still affects the environmental system and human health, the need to develop innovative membranes has become imperious. Lately, researchers have focused on developing novel materials to help diminish the contamination problem. The aim of present research was to obtain innovative adsorbent composite membranes based on a biodegradable polymer, alginate, to remove toxic pollutants. Of all pollutants, lead was chosen due to its high toxicity. The composite membranes were successfully obtained through a direct casting method. The silver nanoparticles (Ag NPs) and caffeic acid (CA) from the composite membranes were kept at low concentrations, which proved enough to bestow antimicrobial activity to the alginate membrane. The obtained composite membranes were characterised by Fourier transform infrared spectroscopy and microscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TG-DSC). Swelling behaviour, lead ion (Pb2+) removal capacity, regeneration and reusability were also determined. Further, the antimicrobial activity was tested against selected pathogenic strains (S. aureus, E. faecalis sp., P. aeruginosa, E. coli and C. albicans). The presence of Ag NPs and CA improves the antimicrobial activity of the newly developed membranes. Overall, the composite membranes are suitable for complex water treatment (removal of heavy metal ions and antimicrobial treatment).

Smart l-borneol-loaded hierarchical hollow polymer nanospheres with antipollution and antibacterial capabilities

Porous organic polymers having well-defined morphologies and designable functionalities are potentially suitable materials for environmental remediation, e.g., for the removal of pollutants from water. However, single materials generally do not simultaneously possess high adsorption abilities and antibacterial performance, as well as easy processibility. Herein, we reported a processible porous polymer which composed swellable hollow spherical morphology and branched L-borneol antibacterial agents. These features endure a valuable capability of pollutant absorption for represented pollutants such as, organic dye (methylene blue), organic compound (bisphenol A), and the heavy metal (Cu2+). In addition, the L-borneol groups and 3D crosslinked hierarchical structure result in enhancement of antibacterial performance against Escherichia coli and Staphylococcus aureus. Moreover, we demonstrate the preparation of the polymer as a fine powder could anchored on the membranes, processed into the tablet, adhered with the polyurethane foams, and assembled as the dye absorption device. The rationally designed polymers by this method show notable potential as adsorbents for water purification and sewage treatment.

CTAB-assisted synthesis of Bi2MoO6 hierarchical microsphere and its application as a novel efficient and recyclable adsorbent in removing organic pollutants

Herein we have synthesized Bi2MoO6 (BMO) hierarchical microspheres via a solvothermal method using hexadecyl trimethyl ammonium bromide (CTAB) as surfactant, and demonstrated that the synthesized BMO can be used as an efficient and recyclable adsorbent for removing organic pollutants. By using methylene blue (MB) as the target pollutant, the adsorption kinetics, adsorption isotherms and adsorption thermodynamics of MB onto the BMO adsorbent were systematically investigated. The effects of pH, temperature and adsorbent dosage on the MB adsorption by BMO were predicted by response surface methodology (RSM) with Box-Behnken design (BBD). It is interestingly demonstrated that the BMO adsorbent can be easily regenerated via a simple calcination process in air and exhibits excellent reusability. To promote the practical application of the BMO adsorbent in water purification, we have further compared its adsorption capability in removing 18 kinds of organic pollutants (including various organic dyes, antibiotics and other serious organic pollutants) at different acidic-alkaline environments. In the normal and alkaline (pH 12) environments, the highest adsorption is observed for Congo red (CR) with qe = 216.331 and 232.723 mg g−1, respectively; whereas in the acidic environment (pH 2), the highest adsorption is observed for eriochrome black T (EBT) with qe = 64.362 mg g−1. Based on the experimental results, the involved adsorption mechanism was analyzed.

Commercial synthetic hydrotalcite as an adsorbent nanomaterial for removal of bacteria from contaminated water

Layered double hydroxides (LDHs) are regarded as potential adsorbents for water treatment from a wide range of pollutants. However, there are only a few studies concerning application of LDHs for elimination of microorganisms from aquatic systems. In this work, experiments were conducted to investigate the efficiency of commercial synthetic hydrotalcite Mg6Al2(CO3)(OH)16∙4H2O as an adsorbent for water purification from fecal indicator bacteria Escherichia coli BIM B-378 and Enterococcus faecalis BIM B-1530. Our findings indicate that exposure for 4 h to hydrotalcite (5 g/L) in suspension resulted in the removal of about 40% of coliforms and 25% of enterococci from water, at a high bacterial load (2×1010 CFU/L), and the removal efficiency of E. coli and E. faecalis did not significantly change when both bacteria were present in water. In addition, the percentage of removed bacteria increased with increasing of hydrotalcite concentration in the suspension (0.5 to 10 g/L), contact time (1-7 h) and decrease of pH (5.5), and decreased at low incubation temperature (16°C). Finally, hydrotalcite did not exhibit bactericidal activity and retention of bacteria was found to be reversible. Therefore, our findings suggest that commercial synthetic hydrotalcite could be potentially used in technologies of water treatment from bacterial contamination.

Recent Developments in the Removal of Dyes from Water by Starch-Based Adsorbents.

Starch-based adsorbents have demonstrated excellent potential for the removal of various noxious dyes from wastewater. This review critically evaluates the recent progress in applications of starch-based adsorbents for the removal of dyes from water. The synthesis methods of starch-based composites and their effects on physicochemical characteristics of produced adsorbents are discussed. The removal of various dyes by starch-based adsorbents are described in detail, with emphasis on the effect of key parameters, adsorption mechanism and their reusability potential. The key challenges related to the synthesis and applications of starch-based adsorbents in water purification are highlighted. Based on the research gaps, recommendations for future research are made. The evaluation of starch-based adsorbents would contribute to the development of sustainable water treatment options in near future.

PURIFICATION OF UNDERGROUND WATER USING SORBENT BASED ON SILICONY ROCK-FLASK OF WEST KAZAKHSTAN

Currently, the Republic of Kazakhstan maintains an intense environmental situation that is associated with an anthropogenic impact on water supply sources. Technically, providing the required amount of water is a feasible task, but the supplied water must be of a certain quality and comply with drinking water supply standards. In this regard, it is a necessity today to constantly monitor the quality of underground water sources used to purify them from harmful impurities using the most effective and readily available natural sorbents. The paper presents the results of studies of the physical and chemical properties of groundwater from wells No. 48 belonging to LLP "ESCEIPA" and the village of Dzhangala, West Kazakhstan region. A siliceous rock - a flask of Western Kazakhstan was used as an adsorbent for water purification. Acid activation was carried out to increase the sorption capacity of the flask. Permanganate oxidizability, sulfate ions, and dry residue were determined in the studied water samples before and after treatment, the following. The studies were carried out with the original and modified flask. The experimental data obtained showed that the best results were achieved after acid activation of the sorbent. Thus, the content of mineral salts has decreased by 2 times, the permanganate oxidizability for the "ESCEIPA" water sample is below the permissible concentration, and the content of sulfate ions is close to the technical conditions. It has been proved that it is possible to use a flask for groundwater treatment, and acid modification improves the sorption characteristics of the material under study.

Modern Carbon-Based Materials for Adsorptive Removal of Organic and Inorganic Pollutants from Water and Wastewater.

Currently, a serious threat for living organisms and human life in particular, is water contamination with persistent organic and inorganic pollutants. To date, several techniques have been adopted to remove/treat organics and toxic contaminants. Adsorption is one of the most effective and economical methods for this purpose. Generally, porous materials are considered as appropriate adsorbents for water purification. Conventional adsorbents such as activated carbons have a limited possibility of surface modification (texture and functionality), and their adsorption capacity is difficult to control. Therefore, despite the significant progress achieved in the development of the systems for water remediation, there is still a need for novel adsorptive materials with tunable functional characteristics. This review addresses the new trends in the development of new adsorbent materials. Herein, modern carbon-based materials, such as graphene, oxidized carbon, carbon nanotubes, biomass-derived carbonaceous matrices—biochars as well as their composites with metal-organic frameworks (MOFs) and MOF-derived highly-ordered carbons are considered as advanced adsorbents for removal of hazardous organics from drinking water, process water, and leachate. The review is focused on the preparation and modification of these next-generation carbon-based adsorbents and analysis of their adsorption performance including possible adsorption mechanisms. Simultaneously, some weak points of modern carbon-based adsorbents are analyzed as well as the routes to conquer them. For instance, for removal of large quantities of pollutants, the combination of adsorption and other methods, like sedimentation may be recommended. A number of efficient strategies for further enhancing the adsorption performance of the carbon-based adsorbents, in particular, integrating approaches and further rational functionalization, including composing these adsorbents (of two or even three types) can be recommended. The cost reduction and efficient regeneration must also be in the focus of future research endeavors. The targeted optimization of the discussed carbon-based adsorbents associated with detailed studies of the adsorption process, especially, for multicomponent adsorbate solution, will pave a bright avenue for efficient water remediation.

Novel Immobilized Ligand on Polymer Matrix as Adsorbent for Water Purification

Abstract A novel polymer material that is capable of adsorption of Pb2+ and Cu2+ in aqueous solutions has been synthesized. 3-Aminopropyltriethoxysilane was reacted with tetraethylethoxysilane in methanol and aqueous solution of HCl to yield 3-aminopropypolysiloxane (APP). Reacting the APP with ethylchloroacetate in triethylamine yielded a functionalized 3-aminopropypolysiloxane (FAPP). The FAPP was reacted with urea to yield urea immobilized polysiloxane. FTIR spectra of the APP showed major absorption bands (cm−1) at: 1032.5-1042.7 (Si-O-Si), while the Urea-immobilized polysiloxanes (APPU) showed major absorption bands (cm−1) at: 3200 − 3400 υ(NH), 2929 − 2957 υ(C-H), 1505-1643 (C=O, C=C, C=N), and 1032.5-1042.7 (Si-O-Si). SEM-EDX analysis of APP and APPU showed mean pore volumes (nm3) of 113.49 ± 7.91 and 44.89 ± 7.44 respectively, and elemental composition (%) as follows: APP, O (36.68), Si (39.91); FAPP, O (29.43), Si (41.64), Cl (9.06); APPU, O (32.15), Si (28.42), N (25.42). APP maximum percentage adsorption of Pb2+ and Cu2+ in simulated water were 79.44 and 74.81 respectively, while APPU maximum percentage adsorption of Pb2+ and Cu2+ were in the range of 78.36 − 85.44 and 79.63 − 82.87 respectively. The maximum percentage adsorption of Pb2+ and Cu2+ which indicate the sorption capacities of the adsorbents occurred within the pH range of 8-10, contact time between 70-90 min, metal ion concentration of 20-25 ppm, dosage of adsorbent of 0.01 − 0.03 g for Pb2+ adsorption, and 0.04 − 0.05 g for Cu(II), and at a temperature of 90°C. The statistical analyses showed significant difference in the means of the effects of pH, time and concentration as F > Fcrit, except in the case of contact time for Cu2+. Temkin isotherm gave values of R2 in the range of 0.9210 − 0.9735 and best fitted the adsorption process. The urea immobilized polysiloxane (APPU) exhibited very high potential for adsorption of Pb2+ and Cu2+ in industrial effluent up to 100 %.

Study of Different Morphology of Zinc Hydroxide Salt as Adsorbent of Azo Dyes

AbstractIn this study, zinc layered hydroxide salts (Zn‐LHS) intercalated with dodecyl sulfate (DDS) anion in nanocone morphology (LHS‐NC) and conventional stone‐like co‐precipitation LHS phases (LHS‐CO) were investigated as adsorbent of Orange G (OG) and Sunset Yellow (SY) dye. LHS‐NC was prepared by urea hydrolysis method, while LHS‐DDS was prepared by co‐precipitation method. XRDP, FTIR, and SEM were used to characterize their structure and showed the formation of layered compounds with very well layered stacking with nanocone and conventional layer stone morphology. After OG and SY adsorption, the results (XRDP, FTIR, UV‐Vis, Zetametry) showed that the Freundlich adsorption isotherms had been well fitted, and both OG and SY dyes were intercalated in interlayer space of LHS, where LHS‐CO and LHS‐NC present high uptake capability of SY dye remotion equal a 227.79 and 442.48 (mg g−1) while OG adsorption capability were 2.52 and 6.39 (mg g−1), respectively. For the kinetics study, the best fit was obtained by the pseudo‐second‐order model, whereas the results of intraparticle diffusion show a one‐step adsorption process. Hence, this study demonstrated Zn‐LHS in nanocone morphology, and conventional stone‐like co‐precipitation phase makes them potentially attractive adsorbents in water purification.

Encapsulated anion-dominated photocatalytic and adsorption performances for organic dye degradation and oxoanion pollutant capture over cationic Cu(i)-organic framework semiconductors.

Decontamination of industrial wastewater containing toxic organic dye molecules and oxoanions is urgently desirable for environmental sustainability and human health. Water-stable porous metal-organic frameworks (MOFs) have emerged as highly efficient photocatalysts and/or adsorbents for water purification through controllable integration of the constitutive requirements. To reveal the inclusion anion effect of microporous MOFs on wastewater treatment, two isostructural MOFs incorporating positive charge and semiconductive characteristics, {[Cu(tpt)]·3H2O·0.5SO4}n (1) and {[Cu(tpt)]·2H2O·ClO4}n (2, tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine), have been synthesized and employed as dual-functional materials for both dye photodegradation and oxoanion removal. The two MOFs possess the same 3-fold interpenetrating cationic backbones but are encapsulated by highly disordered sulfate or perchlorate in the open channels. These included anions have significantly tuned the hydrophilicity of the channels, extended the visible-light absorption, optimized the bandgap and decreased the conduction band potential. Under the low-energy irradiation of a 30 W LED lamp, MOF 1 has selectively and efficiently degraded rhodamine B compared to 2 with accelerated kinetics, resulting from the stronger reduction ability and less migration resistance of the photogenerated electrons. Instead, MOF 2 can quickly capture harmful MnO4- and Cr2O72- by exchanging with the entrapped ClO4-, with maximum adsorption amounts of 557 and 168 mg g-1, respectively, under ambient conditions. The improved decolorization of the aqueous solution over 2 benefits essentially from the shape and charge memory effect and the smaller hydration energy of ClO4- than SO42-. These interesting observations highlight the importance of the included anions inside the porous MOF semiconductors on wastewater treatment.

EVALUATION OF PHOSPHATE AND AMMONIUM ADSORPTIONDESORPTION OF SLOW PYROLYZED WOOD BIOCHAR

Biochar is attracting attention as a soil amendment and organic/inorganic adsorbent for water purification. Proper use of biochar in such cases requires understanding of the mechanisms of nutrient adsorption and desorption on biochar. In this study, slow pyrolyzed wood biochar s were prepared at temperatures 400 and 600 C with retention time of 60 and 120 minutes to investigate their phosphate and ammonium adsorption capacities. The effects of pyrolysis process conditions and biochar physicochemical properties on potential adsorption capacity were evaluated. Results of adsorption kinetics showed that both pseudo-first-order and pseudosecond-order models could well predict the adsorption kinetics of phosphate and ammonium indicating that the chemical adsorption was one of the main mechanisms of phosphate and ammonium absorption. Langmuir-Freundlich isotherm was the best-fit model for ammonium adsorption which means the occurrence of chemical adsorption on heterogeneous surface whilst Langmuir isotherm agreed well with the phosphate adsorption. For different biochar s, ammonium adsorption capacity ranged from about 0.34 to 5.3 mg/g and phosphate adsorption capacity ranged from about 0.6 to 42.2 mg/g. Phosphate adsorption capacity improved with increasing temperature and retention time of pyrolysis process. However, higher ammonium adsorption which was observed in lower pyrolysis temperature and residence time can be attributed to more oxygen-containing functional groups. Both phosphate and ammonium adsorptions-desorption by biochar are more strongly related to solution pH, and maximum adsorption capacities were observed at pH of 7 and 3 for ammonium and phosphate, respectively.

OBTAINING DERIVATIVES OF HUMIC SUBSTANCES FROM OXIDIZED COAL AND STUDY OF PHYSICO-CHEMICAL AND ADSORPTION PROPERTIES

In the work, a chemical analysis of humic substances based on oxidized coal of the Maikuben basin (Kazakhstan) is carried out. Humic acids were obtained on the basis of potassium humates by acidification with a 20% acid solution to pH = 3-4.5. The optimal conditions for obtaining nitrohumic acids from oxidized coals are: the duration of the process is 3 hours, the ratio of S:L = 1:5, the content of nitric acid is 64%, sulfuric acid is 96% and the composition of the nitrating mixture is 1:1 (g/g). Amminohumic derivatives were obtained in the presence of a 3% aqueous solution of ammonia using mechanical activation and ultrasonic treatment. The samples obtained were tested as an adsorbent for water purification from heavy metals. Humic acids and aminohumate showed the highest degrees of purification for zinc (99.0-100.0%) and cadmium (80.0-96.7%), and nitrohumic acid showed a high adsorption capacity for heavy metals like copper - 100.0 % and lead 82.9%. This is due to the fact that when interacting with heavy metals, humic acids and their derivatives (amino and nitro) form chelate complexes due to carboxyl, phenolic, nitro and amino groups. As a result of the study, the possibility of using them as non-toxic available sorbents for the purification of heavy metals in aqueous media has been shown.

Magnetic graphene-based nanocomposites as highly efficient absorbents for Cr(VI) removal from wastewater.

Due to the merits of their high adsorption and convenient separation, magnetic graphene-based composites have become a promising adsorbent in terms of wastewater treatment. However, recycling and regeneration properties of magnetic graphene-based composites are still a conundrum, which remains to be resolved. Here, Fe3O4/reduced graphene oxide (RGO) (Fe3O4/RGO) nanocomposites were synthesized by one-step solvent-thermal reduction route and used as adsorbents for water purification. It was encouraging to find that the nanocomposites possessed many intriguing properties in removing of Cr(VI) ions, including high adsorption efficiency and excellent recycling and regeneration property. The results indicated that the magnetic separation process of the Fe3O4/RGO nanocomposites only took less than 5s and the maximum removal efficiency of Cr(VI) reached 99.9% under the optimum experimental conditions. Most significantly, the adsorption rate of Cr(VI) can still be as high as 98.13% after 10cycles and the single recycle quality of the nanocomposites can maintain at more than 80%. As a result, the Fe3O4/RGO nanocomposites could be a potential adsorbent for removing heavy metal ions effectively, especially in environmental protection and restoration.