Zhanna K. Zhatkanbayeva

Biochar has emerged as a promising soil amendment for mitigating heavy metal contamination in agricultural systems. This study investigates the effects of biochar on cadmium (Cd) and copper (Cu) uptake, plant growth, oxidative stress, and physiological responses in lettuce (Lactuca sativa L.) plants exposed to different metal concentrations. Results indicate that biochar significantly influenced Cd bioavailability, reducing its accumulation in plant tissues by up to 31.9% and alleviating oxidative stress, with malondialdehyde and proline levels decreasing by up to 51.0% and 60.2%, particularly at higher application rates (5%). Cd-exposed plants treated with biochar exhibited an improved fresh weight (+22.6%), lower malondialdehyde and proline levels, and enhanced the chlorophyll content (+14.9% to 24.1%) compared to untreated plants. The bioaccumulation factor for Cd decreased (up to 31.8%) while the immobilization index (II) increased, confirming the role of biochar in limiting Cd mobility in soil. In contrast, Cu uptake remained consistently low across all treatments, with a significant reduction observed only at higher contamination levels (up to −34.2%). Biochar contributed to Cu immobilization, reflected in increased II values, and enhanced the plant biomass and chlorophyll content under Cu exposure (+15.4% and up to +24.1%, respectively), suggesting a partial alleviation of Cu toxicity. These findings highlight biochar’s potential in heavy metal remediation, particularly for Cd, by reducing bioavailability and improving plant resilience. However, its role in Cu-contaminated soils is mainly through immobilization rather than uptake reduction.

To develop membranes capable of efficient and switchable separation of emulsions under variable pH conditions, pH-responsive surfaces were engineered by modifying poly(ethylene terephthalate) track-etched membranes (PET TeMs) via a two-step UV-initiated RAFT graft polymerization. Initially, polystyrene (PS) was grafted to render the surface hydrophobic, followed by the grafting of poly(methacrylic acid) (PMAA) to introduce pH-responsive carboxyl groups. Optimized conditions (117 mM MAA, RAFT:initiator 1:10, 60 min UV exposure at 10 cm) resulted in PET TeMs-g-PS-g-PMAA surfaces exhibiting tunable wettability, with contact angles shifting from 90° at pH 2 to 65° at pH 9. Successful grafting was confirmed by FTIR, AFM, SEM, TGA, and TB dye sorption. The membranes showed high separation efficiency (up to 99%) for both direct and reverse emulsions. In direct emulsions, stable flux values (70 to 60 L m-2 h-1 for cetane-in-water and 195 to 120 L m-2 h-1 for o-xylene-in-water) were maintained over five cycles at 900 mbar, indicating good antifouling behavior. Reverse emulsions exhibited initially higher flux, but stronger fouling; however, flux recovery reached 91% after cleaning. These findings demonstrate the potential of PET TeMs-g-PS-g-PMAA as switchable, pH-responsive membranes for robust emulsion separation.

This study investigated if the foliar application of wood distillate (WD, a by-product of biomass pyrolysis, containing bioactive compounds, including organic acids and phenols) influences some key parameters (fresh weight, photosynthetic efficiency, antioxidant compounds, stress-related biochemical markers, and mineral content) of basil plants, used as a model crop, grown under water-limited conditions. The experimental setup included control and WD treatments (applied via foliar application at 0.2%) under three drought levels: no stress, moderate, and high stress. The results indicated that the application of WD contributed to improving the fresh weight, chlorophyll, reduced oxidative stress, and stable levels of essential nutrients across varying drought intensities. These outcomes highlight the potential of WD as an effective biostimulant for enhancing drought tolerance in basil plants under water deficiency.

In Kazakhstan, the issue of providing the population with quality drinking water remains one of the topical and important issues. Despite significant efforts in the field of infrastructure and water treatment technologies, many regions of Kazakhstan still face problems of pollution and insufficient water resources. In this regard, the development of effective water treatment methods is of particular importance. This study considers the issue of wastewater treatment by the combined method of forward and reverse osmosis, which is a key direction in modern water treatment. The relevance of the work is the use of integration of forward osmosis methods with the process of adsorption by powdered activated carbon in wastewater treatment. The use of powdered activated carbon in the process of wastewater treatment leads to a reduction in the content of organic matter, which are water pollutants. As a result of the experiment with pretreatment of wastewater with powdered activated carbon, a decrease in the level of chemical oxygen demand (COD) in wastewater from 538 mg O/dm3 to 256 mg O/dm3 was observed, as well as a relative decrease in the concentration of other indicators. The draw solution in the form of 1.5 M NaCl gradually drawing water molecules from the feed solution pretreated with activated carbon on the tenth day had a concentration of 0.425 M absorbing 2.529 liters of water entering through the membrane that is 27.6% more than the control version of the experiment. The effectiveness of integrated methods lies in the successful combination of different technologies to improve water treatment processes and ensure the availability of clean water not only in Kazakhstan, but also in different parts of the world.

Stimuli-responsive membranes play an important role in the fields of biomedicine, food and chemical industries, and environmental applications, including separation of water–oil emulsions. In this study, we present a method to fabricate pH-sensitive membranes using UV-initiated RAFT graft copolymerization of styrene (ST) and acrylic acid (AA) on poly(ethylene terephthalate) (PET) track-etched membranes (TeMs). The optimization of polymerization conditions led to successful grafting of polystyrene (PS) and poly(acrylic acid) (PAA) onto PET TeMs, resulting in membranes with stable hydrophobicity and pH change responsiveness. The membranes show a contact angle of 65° in basic environments (pH 9) and 97° in acidic environments (pH 2). The membranes were characterized by atomic force microscopy (AFM), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), thermogravimetric analyses (TGA), Fourier transform infrared spectroscopy (FTIR), contact angle (CA) methods. The PET TeMs-g-PS-g-PAA exhibited good performance in separating water–oil emulsions with a high efficiency of more than 90% and flux for direct chloroform–water 2500 L m⁻² h⁻¹ and reverse emulsions of benzene–water 1700 L m⁻² h⁻¹. This method of preparing stimuli-responsive membranes with controlled wettability and responsiveness to environmental pH provides versatility in their use in separating two types of emulsions: direct and reverse.

In this work, we have developed a method for the preparation of pH-responsive track-etched membranes (TeMs) based on poly(ethylene terephthalate) (PET) with pore diameters of 2.0 ± 0.1 μm of cylindrical shape by RAFT block copolymerization of styrene (ST) and 4-vinylpyridine (4-VP) to be used in the separation of water–oil emulsions. The influence of the monomer concentration (1–4 vol%), the molar ratio of RAFT agent: initiator (1:2–1:100) and the grafting time (30–120 min) on the contact angle (CA) was studied. The optimal conditions for ST and 4-VP grafting were found. The obtained membranes showed pH-responsive properties: at pH 7–9, the membrane was hydrophobic with a CA of 95°; at pH 2, the CA decreased to 52°, which was due to the protonated grafted layer of poly-4-vinylpyridine (P4VP), which had an isoelectric point of pI = 3.2. The obtained membranes with controlled hydrophobic-hydrophilic properties were tested by separating the direct and reverse “oil–water” emulsions. The stability of the hydrophobic membrane was studied for 8 cycles. The degree of purification was in the range of 95–100%.

The paper describes the separation of an oil–water emulsion by filtration using poly(ethylene terephthalate) track-etched membranes (PET TeMs) with regular pore geometry and narrow pore size distribution. PET TeMs were modified with trichloro(octyl)silane to increase their hydrophobic properties. Conditions for the modification of PET TeMs with trichloro(octyl)silane were investigated. The results of changes in the pore diameters and the contact angle depend on the concentration of trichloro(octyl)silane and the soaking time are presented. The obtained samples were characterized by FTIR, AFM, SEM-EDX and gas-permeability test. Chloroform–water and cetane–water emulsions have been used as a test liquid for oil–water separation.