Electroosmotic dewatering of dredged sediments: bench-scale investigation

The Indiana Harbor (Indiana, USA) has not been dredged since 1972 due to lack of a suitable disposal site for dredged sediment. As a result of this, over a million cubic yards of highly contaminated sediment has accumulated in the harbor. Recently, the United States Army Corps of Engineers (USACE) has selected a site for the confined disposal facility (CDF) and is in the process of designing it. Although dredging can be accomplished rapidly, the disposal in the CDF has to be done slowly to allow adequate time for consolidation to occur. The sediment possesses very high moisture content and very low hydraulic conductivity, which cause consolidation to occur slowly. Consolidation of the sediment is essential in order to achieve adequate shear strength of sediments and also to provide enough air space to accommodate the large amount of sediment that requires disposal. Currently, it has been estimated that if a one 3-foot (0.9-m) thick layer of sediment was disposed of at the CDF annually, it would take approximately 10 years to dispose of all the sediment that is to be dredged from the Indiana Harbor. This study investigated the feasibility of using an electroosmotic dewatering technology to accelerate dewatering and consolidation of sediment, thereby allowing more rapid disposal of sediment into the CDF. Electroosmotic dewatering essentially involves applying a small electric potential across the sediment layer, thereby inducing rapid flow as a result of physico-chemical and electrochemical processes. A series of bench-scale electrokinetic experiments were conducted on actual dredged sediment samples from the Indiana Harbor to investigate dewatering rates caused by gravity alone, dewatering rates caused by gravity and electric potential, and the effects of the addition of polymer flocculants on dewatering of the sediments. The results showed that electroosmotic dewatering under an applied electric potential of 1.0VDC/cm could increase the rate of dewatering and consolidation by an order of magnitude as compared to gravity drainage alone. Amending the sediment with polymers at low concentrations (0.5-1% by dry weight) will enhance this dewatering process; however, the optimal polymer concentration and the cost-effectiveness of using polymers should be investigated further.     

Nitrogen-enriched micro-mesoporous carbon derived from polymers organic frameworks for high-performance capacitive deionization

Nitrogenization is an effective method for improving the capacitive deionization（CDI） performance of porous carbon materials. In particular, polymer organic frameworks with heteroatom doping, containing an ordered pore structure and excellent electrochemical stability, are ideal precursors for carbon materials for high-performance CDI. In this study, a nitrogen-enriched micro-mesoporous carbon（NMC） electrode was fabricated by carbonizing a Schiff base network-1 at 500, 600, and 700 °C. Scanning ...     

典型热塑性聚合物热解行为研究

利用热失重分析仪采用不同的加热速率对典型热塑性聚合物PP(聚丙烯)、PE(聚乙烯)和PMMA(聚甲基丙烯酸甲酯)在空气氛围中的热解行为进行了研究,通过热失重TG和微商热失重DTG分析了三种聚合物的热解过程及加热速率对热解过程的影响,通过Coats-Redfern方法建立了聚合物的热解动力学模型,并分析讨论了聚合物的热解机理和氧气对热解的影响,最后通过计算曲线和实验曲线的比较,验证了该文聚合物热解动力学模型的可靠性。     

The Effect of Nanoclays on the Properties of PLLA-modified Polymers Part 1: Mechanical and Thermal Properties

Organically modified montmorillonite clays were incorporated at a 5% loading level into film grade of poly-L-lactic acid (PLLA) using a variety of masterbatches based on either semi-crystalline or amorphous poly-(lactic acid), as well as biodegradable aromatic aliphatic polyester. The PLLA masterbatches and compounded formulations were prepared using a twin screw compounding extruder, while the films were prepared using a single screw cast film extruder. The thermal and mechanical properties of the films were examined in order to determine the effect of the clay and different carriers on the polymer–clay interactions. In the optimal case, when a PLLA-based masterbatch was used, the tensile modulus increased by 30%, elongation increased by 40%, and the cold crystallization temperature decreased by 15 °C, compared to neat PLLA. The properties improvement of PLLA films containing nano clays demonstrated the possibility to extend the range of biodegradable film applications, especially in the field of packaging.     

Biodegradability of PMMA Blends with Some Cellulose Derivatives

High polymer blends of Polymethyl methacrylate (PMMA) with cellulose acetate (CA) and Cellulose acetate phthalate (CAP) of varying blend compositions have been prepared to study their biodegradation behavior and blend miscibility. Films of PMMA–CA, and PMMA–CAP blends have been prepared by solution casting using Acetone and Dimethyl formamide(DMF) as solvents respectively. Biodegradability of these blends has been studied by four different methods namely, soil burial test, enzymatic degradation, and degradation in phosphate buffer and activated sludge degradation followed by water absorption tests to support the degradation studies. Degradation analysis was done by weight loss method. The results of all the tests showed sufficient biodegradability of these blends. Degradability increased with the increase in CA and CAP content in the blend compositions. The miscibility of PMMA–CA and PMMA–CAP blends have been studied by solution viscometric and ultrasonic methods. The results obtained reveal that PMMA forms miscible blends with either CA or CAP in the entire composition range. Miscibility of the blends may be due to the formation of hydrogen bond between the carbonyl group of PMMA and the free hydroxyl group of CA and CAP.     

The problem of allergy in ecotoxicology of polymeric materials

In the program of initial toxicological test, the estimation of allergenic activity of some names of polymeric compositions, which are used in the polygraphic industry and when painting and decorating dwelling houses and social purpose premises, had been carried out. Most of the investigated compositions have different degrees of allergenicity. In order to unify the works in this field, we suggest the basic circuit of the estimation of allergenicity of polymeric materials, the final stage of which provides for the compiling of register of potentially allergenic polymeric materials.     

A possible simplification of the Goss-modified Abraham solvation equation

Abraham solvation equations find widespread use in environmental chemistry and pharmaco-chemistry. Recently Goss proposed a modified Abraham solvation equation. For various partitioning processes, the present study investigates the consequences for the fit when the Abraham solvation parameter V is left out of this modified solvation equation. For air-organic solvent partition, the Abraham solvation parameter V can be omitted from the Goss-modified Abraham solvation equation without any loss of statistical quality. For air–water partitioning, organic biphasic system partitioning, as well as water-organic solvent partitioning, omitting the V parameter from the Goss-modified Abraham solvation equation leads to only a small deterioration of statistic quality.     

Microbial biodegradation of plastics: Challenges,opportunities, and a critical perspective

● Health hazards of plastic waste on environment are discussed. ● Microbial species involved in biodegradation of plastics are being reviewed. ● Enzymatic biodegradation mechanism of plastics is outlined. ● Analytical techniques to evaluate the plastic biodegradation are presented. The abundance of synthetic polymers has increased due to their uncontrolled utilization and disposal in the environment. The recalcitrant nature of plastics leads to accumulation and saturation in the environment, which is a matter of great concern. An exponential rise has been reported in plastic pollution during the corona pandemic because of PPE kits, gloves, and face masks made up of single-use plastics. The physicochemical methods have been employed to degrade synthetic polymers, but these methods have limited efficiency and cause the release of hazardous metabolites or by-products in the environment. Microbial species, isolated from landfills and dumpsites, have utilized plastics as the sole source of carbon, energy, and biomass production. The involvement of microbial strains in plastic degradation is evident as a substantial amount of mineralization has been observed. However, the complete removal of plastic could not be achieved, but it is still effective compared to the pre-existing traditional methods. Therefore, microbial species and the enzymes involved in plastic waste degradation could be utilized as eco-friendly alternatives. Thus, microbial biodegradation approaches have a profound scope to cope with the plastic waste problem in a cost-effective and environmental-friendly manner. Further, microbial degradation can be optimized and combined with physicochemical methods to achieve substantial results. This review summarizes the different microbial species, their genes, biochemical pathways, and enzymes involved in plastic biodegradation.     

On the feasibility of producing polymer–metal composites via novel variant of friction stir processing

In this study a novel variant of friction stir processing was developed for producing of polymer metal surface or bulk composites in order to enhance the mechanical, electrical and thermal properties. For this purpose, a novel tooling system was designed consists of a rotating pin, a stationary shoulder and a heating system located inside the shoulder. In present paper, for preliminary study high-density polyethylene and copper powder was selected as polymeric matrix and metallic additive, respectively. Surface quality, microstructure, ultimate tensile strength and the modulus of elasticity were determined for each prepared sample. From experimental tests, it was found that this approach is an efficient method for producing of polymer–metal composites.     

Microplastics in the atmosphere of Ahvaz City, Iran

Airborne particulate matter (PM) with an aerodynamic size cutoff of 10 µm (PM10) has been collected using a high volume air sampler at two locations (urban and residential) in the city of Ahvaz, Iran, for sixteen 24-hour periods over four months (late summer to early winter). Microplastics (MPs) in the PM were isolated after sample digestion and were subsequently characterised by established techniques. All MPs sampled (n = 322) were of a fibrous nature, with polyethylene terephthalate, nylon and polypropylene being the dominant polymers and consistent with textiles and fabrics as the principal source. Despite a distinct seasonality (temperature and wind) over the study period, the abundance, size and colour of the fibres exhibited no clear temporal trend, and no clear differences were observed between the two sites. Concentrations of MPs ranged from none detected to about 0.017/m³ (median = 0.0065/m³) and are at the low end of ranges reported in the recent literature for various urban and remote locations. While some MPs may have a local origin, the weathering of other MPs and their acquisition of extraneous geosolids and salts suggests that long-range transport is also important. Back-trajectory calculations indicate that regional sources are mainly to the north and west of Ahvaz, but a southerly, maritime source is also possible in late autumn. Although concentrations of MPs in the atmosphere are well below those encountered in indoor air, further studies are required to elucidate their potential ecological impacts.