Residual Plastic Research Articles

Thickness effects of polyethylene and biodegradable film residuals on soil properties and dryland maize productivity

Plastic film residuals are increasingly remaining in cultivated lands. However, it is a critical issue how residual plastic type and thickness affect soil properties and crop yield. To address this issue, in situ landfill was conducted using thick polyethylene (PEt1), thin polyethylene (PEt2), thick biodegradable (BIOt1), thin biodegradable (BIOt2) residues, and CK (control) with no residues landfill in a semiarid maize field. The findings demonstrated that the impact of various treatments on soil characteristics and maize yield varied considerably. Soil water content decreased by 24.82% in PEt1 and 25.43% in PEt2, compared to BIOt1 and BIOt2, respectively. BIOt2 treatment increased soil bulk density by 1.31 g cm−3 and lowered soil porosity by 51.11%, respectively; it also elevated the silt/clay proportion by 49.42% relative to CK. In contrast, microaggregate composition in PEt2 was higher (43.02%). Moreover, BIOt2 lowered soil nitrate (NO3−) and ammonium (NH4+) content. Compared with other treatments, BIOt2 resulted in significantly higher soil total nitrogen (STN) and lower SOC/STN. Finally, BIOt2 exhibited the lowest water use efficiency (WUE) (20.57 kg ha−1 mm−1) and yield (6896 kg ha−1) among all the treatments. Therefore, BIO film residues exhibited detrimental impacts on soil quality and maize productivity compared to PE film ones. Considering film thickness, thin residual films more evidently influenced soil quality and maize productivity than thick film ones.

Elasto-plastic analysis and optimal design of composite integral abutment bridge extended with limited residual plastic deformation

Due to the growing significance of structural theories concerning the composite structure analysed and designed plastically, this paper introduces a new optimisation method for controlling the plastic behaviour of a full-scale composite integral abutment bridge by employing complementary strain energy of residual forces that existed within the reinforcing rebars. Composite bridges are structures made of components such as steel and concrete, which are frequent and cost-effective building methods. Thus, various objective functions were used in this work when applying optimum elasto-plastic analysing and designing the composite integrated bridge structure that was tested experimentally in the laboratory. In contrast, the plastic deformations were constrained by restricting the complementary strain energy of the residual internal forces aiming to find the maximum applied load and the minimum number of steel bars used to reinforce the concrete column part of the structure. The numerical model employed in this paper was validated and calibrated using experimental results, which were considered inside ABAQUS to produce the validated numerical model, using concrete damage plasticity (CDP) constitutive model and concrete data from laboratory testing to solve the nonlinear programming code provided by the authors. This paper presents a novel optimization method using complementary strain energy to control the plastic behaviour of a full-scale composite integral abutment bridge, with the original contribution being the incorporation of residual forces within reinforcing rebars to limit plastic deformations. Following that, a parametric investigation of the various optimisation problems revealed how models performed variously under different complementary strain energy values, which influenced the general behaviour of the structure as it transitioned from elastic to elasto-plastic to plastic; also results showed how the complementary strain energy value is connected with the amount of damaged accrued in both concrete and steel.

Controlled Combustion and Pyrolysis of Waste Plastics: A Comparison Based on Human Health Risk Assessment

Increasing conditions of economic and social well-being have led to an increase in waste production. Among the waste products, a significant portion consists of plastic materials that are popular in the components of consumer goods. For this reason, the conversion of plastic to energy via controlled combustion and plastic to fuel via thermal/catalytic pyrolysis or gasification can be proposed to treat the residual heterogeneous mixed plastics that cannot be recovered as individual polymers. The quality and type of fuels that are possible to obtain from these processes are different, as is the quality of their emissions, which generally contain VOCs, PCBs, dioxins, PAHs, and heavy metals. In this work, we propose a methodology based on human health risk assessment to compare controlled combustion and catalytic pyrolysis. Many pathways are analyzed, and pollutant concentrations are computed in the atmosphere, water, vegetables, fish, and food. Exposure is evaluated for inhalation and ingestion routes by taking into account uncertainties. Our results show that the risk profile of catalytic pyrolysis is low. Controlled combustion remains an interesting process, but even if Best Available Technologies (BAT) are adopted, the cancer risk due to PAHs contained in particulate is around the threshold for people living near the plant if a long period of operation is considered.

Effects of practicing long-term mulched drip irrigation on soil quality in Northwest China

Assessing soil quality variation during the prolonged application of mulched drip irrigation (MDI) is critical to comprehend the sustainability of arid agriculture. To investigate the dynamics of crucial soil-quality indicators caused by the long-term application of MDI, the “space instead of time” methodology was adopted, and six fields were selected to represent the primary successional sequence in Northwest China. A total of 21 vital soil attributes from 18 samples were used as soil quality indicators. Based on the soil quality index calculated from the entire datasets, it was observed that long-term MDI practice enhanced soil quality by 28.21 %–74.36 % due to improvements in soil structure (e.g., soil bulk density, three-phase ratio, and aggregates stability) and nutrients (including total carbon, organic carbon, total nitrogen, and available phosphorus). Compared to natural unirrigated soil, soil salinity in 0–200 cm depth significantly decreased by 51.34 %–92.39 % in cotton fields with increasing years of practicing MDI. In addition, long-term MDI practice restructured soil microbial communities and augmented microbial activity by 259.48 %–502.90 % relative to the natural salt-affected soil. However, soil quality stabilized after 12–14 years of MDI application due to accumulated residual plastic fragments, increased bulk density, and reduced microbial diversity. Overall, practicing long-term MDI promotes soil quality and crop yield by promoting soil microbiome structure and function and soil structure. However, long-term mono-cropping with MDI would result in soil compaction and impair microbial activity.

From pupil to the brain: New insights for studying cortical plasticity through pupillometry.

Pupil size variations have been associated with changes in brain activity patterns related with specific cognitive factors, such as arousal, attention, and mental effort. The locus coeruleus (LC), a key hub in the noradrenergic system of the brain, is considered to be a key regulator of cognitive control on pupil size, with changes in pupil diameter corresponding to the release of norepinephrine (NE). Advances in eye-tracking technology and open-source software have facilitated accurate pupil size measurement in various experimental settings, leading to increased interest in using pupillometry to track the nervous system activation state and as a potential biomarker for brain disorders. This review explores pupillometry as a non-invasive and fully translational tool for studying cortical plasticity starting from recent literature suggesting that pupillometry could be a promising technique for estimating the degree of residual plasticity in human subjects. Given that NE is known to be a critical mediator of cortical plasticity and arousal, the review includes data revealing the importance of the LC-NE system in modulating brain plasticity and pupil size. Finally, we will review data suggesting that pupillometry could provide a quantitative and complementary measure of cortical plasticity also in pre-clinical studies.

Unveiling the residual plastics and produced toxicity during biodegradation of polyethylene (PE), polystyrene (PS), and polyvinyl chloride (PVC) microplastics by mealworms (Larvae of Tenebrio molitor)

Evidence for plastic degradation by mealworms has been reported. However, little is known about the residual plastics derived from incomplete digestion during mealworm-mediated plastic biodegradation. We herein reveal the residual plastic particles and toxicity produced during mealworm-mediated biodegradation of the three most common microplastics, i.e., polyethylene (PE), polystyrene (PS), and polyvinyl chloride (PVC). All three microplastics are effectively depolymerized and biodegraded. We discover that the PVC-fed mealworms exhibit the lowest survival rate (81.3 ± 1.5%) and the highest body weight reduction (15.1 ± 1.1%) among the experimental groups by the end of the 24-day experiment. We also demonstrate that the residual PVC microplastic particles are more difficult to depurate and excrete for the mealworms compared to the residual PE and PS particles by using laser direct infrared spectrometry. The levels of oxidative stress responses, including reactive oxygen species, antioxidant enzyme activities, and lipid peroxidation, are also highest in the PVC-fed mealworms. Sub-micron microplastics and small microplastics are found in the frass of mealworms fed with PE, PS, and PVC, with the smallest particles detected at diameters of 5.0, 4.0, and 5.9 µm, respectively. Our findings provide insights into the residual microplastics and microplastic-induced stress responses in macroinvertebrates under micro(nano)plastics exposure.

Development and Testing of a Self-Propelled Machine for Combined Potato Harvesting and Residual Plastic Film Retrieval

A self-propelled machine for combined potato harvesting and residual plastic film retrieval is presented in this paper. The machine was designed collaboratively and built at the College of Mechano-Electronic Engineering of Gansu Agricultural University. It is intended for slow slope and horizontal terraces in hilly and mountainous areas of Northwest China, where regular-size harvesters cannot operate. The machine can realize the combined operations of potato digging, potato separation from soil and plastic film, potato collection and bagging, and residual plastic film retrieval. Through engineering analyses, the main systems of the machine were calculated, and their operating parameters were estimated. These include the digging and lifting device, the potato–plastic-film separation device, and the residual plastic film retrieval device. Field tests were performed at a 0.5 m/s driving speed of the machine, while the linear speed of the lifting chain of the digging and lifting device was 1.5 m/s, the tilting angle of the conveying chain of the potato and plastic film separation device was 50°, its linear speed was 0.6 m/s, and the linear speed of the lifting screen of the circulating lifting device was 0.7 m/s. With these settings, the average productivity of the machine was 0.12 ha/h. The loss rate, damage rate, and potato bruising rate were 1.8%, 1.4%, and 2.8%, respectively; the potato impurity rate was 3.6%; and the residual plastic film retrieval rate was 83%—all above industry standards. This research provides a solution to the problem of mechanized potato harvesting and plastic mulch retrieval on small, slopped plots of land in Northwest China and in other parts of the world where similar conditions exist.

Optimal Elasto-Plastic Analysis of Prestressed Concrete Beams by Applying Residual Plastic Deformation Limitations

This work introduces elasto-plastic analysis of prestressed reinforced concrete beams under different prestressing conditions by limiting the residual plastic behaviour inside the steel bars using complementary strain energy. A non-linear optimal method was used to limit residual plastic deformations in steel bars, including prestressed tendons, used to reinforce beams from two previous research investigations. This was considered by using an optimization approach with an objective function to find the maximum loading while applying constraints on the complementary strain energy of residual internal forces in steel elements to control residual plastic deformations. Thus, an elasto-plastic optimization programme was linked to models simulated by ABAQUS, as concrete was calibrated by the concrete damage plasticity (CDP) model. Some variables were considered regarding the force applied inside prestressed tendons and the number of tendons used inside the models. Thus, limits on complementary strain energy affected load values and model damage where an increase in the permissible strain energy value leads to an increase in the corresponding loading values produced; thus, this produces a higher stress intensity in steel and tension-damaged areas in concrete. Based on these data, many comparisons have been made to determine when beams behaved elastically and how they turned into plastic.

Biodegradation of polyethylene (PE) microplastics by mealworm larvae: Physiological responses, oxidative stress, and residual plastic particles

Biodegradation of petroleum-derived plastics in mealworms has been identified with different plastic products. To date, however, the responses of mealworm larvae to plastic biodegradation have received comparatively little attention. Herein, we tested the physiological responses of mealworm larvae after biodegradation of polyethylene (PE) microplastics and evaluated the impact of supplementing co-diet bran on the PE biodegradation and mealworm homeostasis. Significant weight loss, biomass reduction, and decreased survival rates were found for the PE-fed larvae after the six-week test. The efficient removal of PE, molecular weight reduction of residual polymers, and thermal decomposition signals demonstrated the depolymerization and biodegradation. Supplementing bran significantly enhanced the biomass levels and the survival of larvae but disturbed the PE removal in the intestinal tracts. The frass (excrement) from the larvae fed with PE and PE + bran feedstocks both contained undigested residual microplastics of different sizes with no accumulation of nanoplastics. Additionally, higher levels of reactive oxygen species, antioxidant enzyme activities, and lipid peroxidation were detected for larvae fed with pure PE, whereas the oxidative stress levels could be mitigated by supplementing co-diet bran. These results provide methodological insights into assessing the physiological responses of invertebrates after plastic ingestion or under micro(nano)plastic exposure.

Investigation of Nanoscale Scratching on Copper with Conical Tools Using Particle-Based Simulation

In this study, a modeling approach based on smooth particle hydrodynamics (SPH) was implemented to simulate the nanoscale scratching process using conical tools with different negative rake angles. The implemented model enables the study of the topography of groove profiles, scratching forces, and the residual plastic strain beneath the groove. An elastoplastic material model was employed for the workpiece, and the tool–workpiece interaction was defined by a contact model adopted from the Hertz theory. An in-house Lagrangian SPH code was implemented to perform nano-scratching simulations. The SPH simulation results were compared with nanoscale scratching experimental data available in the literature. The simulation results revealed that the normal force was more dominant compared to the cutting force, in agreement with experimental results reported for a conical tip tool with a 60° negative rake angle. In addition, the simulated groove profile was in good agreement with the groove profile produced in the aforementioned experiment. The numerical simulations also showed that the normal and cutting forces increased with the increase in the scratching depth and rake angle. Although the cutting and ploughing mechanisms were noticed in nano-scratching, the ploughing mechanism was more dominant for increased negative rake angles. It was also observed that residual plastic strain exists below the groove surface, and that the plastically deformed layer thickness beneath a scratched groove is larger for more negative values of the tool rake angle and higher scratching depths.

Optimization of Briquette Fuels by Co-Torrefaction of Residual Biomass and Plastic Waste Using Response Surface Methodology

Combining biomass, a clean and renewable energy source, with waste plastic, which serves as a good auxiliary fuel, can produce high-quality clean fuel. The performance of biomass-derived fuel can be improved by torrefaction. This study optimized the co-torrefaction of fungus bran and polypropylene (PP) waste plastic to obtain clean solid biofuel with high calorific value and low ash content (AC) using response surface methodology. Two sets of mixed biochars were investigated using a multiobjective optimization method: mass yield-higher heating value-ash content (MY-HHV-AC) and energy yield-ash content (EY-AC). PP increased the heat value, decreased AC, and acted as a binder. The optimal operating conditions regarding reaction temperature, reaction time, and PP blending ratio were 230.68 °C, 30 min, and 20%, respectively, for the MY-HHV-AC set and 220 °C, 30 min, 20%, respectively, for the EY-AC set. The MY-HHV-AC set had properties close to those of peat and lignite. Furthermore, compared with that of the pure biochar, the AC of the two sets decreased by 15.71% and 14.88%, respectively, indicating that the prepared mixed biochars served as ideal biofuels. Finally, a circular economy framework for biobriquette fuel was proposed and prospects for preparing pellets provided.

Numerical study of rock-breaking mechanism in hard rock with full PDC bit model in compound impact drilling

Geothermal reservoir rocks have the characteristics of high stress, high hardness and high abrasiveness, which makes the drilling rate low and the drilling cost high, and hinders the application of geothermal energy. Improving drilling efficiency in hard rock strata is the prerequisite for large-scale application of geothermal energy. Impact drilling is considered to be the most effective drilling method in hard formations. PDC (Polycrystalline diamond Compact) bit compound impact drilling is one of the impact drilling methods, which has been widely concerned in recent years. In order to further improve the drilling efficiency of this method, the mechanism of PDC bit compound impact rock breaking is studied. Drucker–Prager criterion was used as rock constitutive relation, equivalent plastic strain was used as rock failure criterion, MSE (mechanical special energy) was used as evaluation method of rock-breaking efficiency, and a three-dimensional simulation model of full-size PDC bit for compound impact rock-breaking was built. The rock breaking law in PDC bit compound rock breaking process and the impact vector angle and impact duration on rock breaking efficiency are analyzed. The results show that the compound impact drilling can effectively alleviate the stick–slip vibration phenomenon, and improve drilling efficiency. In the compound impact mode, compressive stress failure and tensile stress failure occur at the same time, and the tensile stress failure is the main failure mode. The peak stress of the rock is 5.49% larger, and the residual plastic deformation is about 4.28% smaller than that of non-impact mode. With the increase of impact angle, the MSE decreases first and then increases a little. The optimal impact vector angle is in the range of 30°–50°. With the increase of the impact time, the MSE decreases in a wavy manner. In the range of 0.2 ms–1.0 ms, the optimal impact time is 0.8 ms–1.0 ms.

Analysis of the effects of isothermal aging and Laser Shock Peening on the flow properties, fatigue crack growth, and fracture toughness of Inconel 718

Laser Shock Peening (LSP) is a surface treatment that improves the fatigue life and fatigue strength of components by inducing a shallow layer that is characterized by compressive residual stress and plastic deformation. This study investigates the use of LSP on Inconel 718 (IN718) on the fatigue crack growth (FCG) and fracture toughness (FT) of as-received (AR), solution-treated (SOL), and samples aged for 0.5, 4, and 100 h. Experimental results on aged samples established that the hardness of samples 0.5 and 4 h increased due to the precipitation of γ′ and γ″ phases while in the 100 h sample the hardness decreases due to the presence of coarser γ″ phase and intergranular δ-phase. These microstructural features impacted the plastic flow behavior of the different samples which was adequately described using a two-fitting approach to the Voce equation. While thermal aging accelerated the FCG of aged samples, the plastic flow and residual stress induced by the LSP significantly reduces the effect of thermal aging, by reducing the FCG rate and increasing the FT of the IN718 aged samples. Finally, results from EBSD analysis showed that the LSP-induced plastic strain depends on the microstructural transformations that occurred during the aging treatment.

Explicit approach for the in-plane cyclic behaviors of unreinforced masonry structures using finite particle method

Masonry structures, especially historical ones, are vulnerable to earthquakes. Their structural performance subjected to cyclic loadings such as earthquakes should be fully understood before retrofitting. This study proposes an explicit approach for analysis of the in-plane cyclic behavior of masonry structures, combining the finite particle method and an elaborated mesoscale model. The proposed approach is intrinsically dynamic, and it can deal with both quasi-static and dynamic problems in the same framework. Specifically, kinetic damping and static convergence criteria are incorporated to accelerate quasi-static analysis. In the modeling, the rigid element is proposed for bricks based on rigid-body motion assumption. The zero-thickness interface element for mortar joints is derived, and the plastic behaviors in the tension regime, shear regime, and composite regime are developed. Specifically, the strength softening, residual plastic displacement, and stiffness degradation during cyclic loadings are fully considered. A single-story masonry wall subjected to quasi-static loads is analyzed, and the crack lines and horizontal force – rotation curve agree well with those in the experiment. The behavior of a two-story masonry wall subjected to seismic loads is then investigated, and the crack pattern and the first-order frequencies before and after cracking agree well with those in the shaking table test. The results indicate a decrease of the natural frequencies as well as story stiffnesses due to fracture in the mortar joints.

Integrated effects of residual plastic films on soil-rhizosphere microbe-plant ecosystem.

Intensive application of low-density polyethylene mulch films has resulted in substantial accumulation of residual plastics in agricultural soil. Although considerable concerns have been raised on the residual plastic pollution, their impacts on the soil-rhizosphere microbe-plant ecosystem have not been fully elucidated. In this study, we used a pot experiment to determine the effects of residual plastic films with different sizes (La, Ma, Mi and Mx) on properties, enzyme systems and nutrients of soil, composition of rhizosphere microbial community, and physiology, growth and stress response of rice plants. Residual plastic films significantly decreased soil bulk density and increased soil porosity, leading to the alteration of extracellular enzyme activities, and accumulation of dissolved nitrogen (NO3-N+NH4-N). The structures of both bacterial and fungal communities were significantly changed by residual plastic films with rhizosphere microbes more sensitive to small-sized plastics. Plant growth was inhibited to different extents by residual plastic films with different sizes. The weighted gene co-expression network analysis (WGCNA) showed that photosynthesis and carbon fixation of rice plants were repressed by residual plastic films, due to the reduced chlorophyll content and rubisco activity. In addition, the endogenous jasmonic acid and antioxidant enzyme system were induced to activate tolerant responses in rice plants to the stress imposed by residual plastic films. The partial least squares path models (PLS-PMs) revealed that residual plastic films had direct and/or indirect effects on the soil-rhizosphere microbe-plant system.

Microplastics distribution and microbial community characteristics of farmland soil under different mulch methods.

The widespread use of plastic film in agricultural production has resulted in the accumulation of large amounts of residual plastic film in the soil, and most of the plastic residuals eventually break up into microplastics (MPs). However, the effects of different film mulching methods on the soil ecosystems are largely unexplored. Therefore, we investigated the MPs distribution and the physicochemical properties and microbial community structure in the farmland soil tillage layer covered with different mulching method of film. The results indicate that the film mulching method had no significant effect on the soil pH and organic matter content, however, the respiration intensity of the soil covered with mulching film (MF) (60.11-84.99μg/g) and shed film (SF) (56.10-65.68μg/g) was significantly higher than that covered with shed film & mulching film (SMF) (17.25-39.16μg/g). The MPs abundance in the soil covered with MF (1367 particles/kg soil) was significantly higher than that covered with SF (800 particles/kg soil) and slightly higher than that with SMF (1000 particles/kg soil). The small-sized (0-0.5mm) MPs abundance was increased with the tillage layer depth (0-20cm), while the large-sized (1-5mm) MPs abundance was the opposite. In addition, in the soil covered with agricultural film, the dominant phylum and genera of the bacteria were Proteobacteria (relative abundance was 64.06 %) and Pseudomonas (13.16 %), respectively. In the soil without agricultural film application as a control treatment, the diversity of the soil bacterial community was higher than that in the soil covered with agricultural film, and the relative abundances of the top 10 genera were all less than 5 %. Overall, this study provides essential information for understanding the effects of different film mulching methods on the agricultural systems. Overall, this study provides essential information for understanding the effects of different film mulching methods on the distribution of MPs and the biogeochemical properties of farmland soils.

Reduction of Residual Stresses in Cold Drawn Pearlitic Steel by a Soft Secondary Wire Diameter Reduction

In this paper, the effects of the skin pass technique on the residual stress and plastic strain fields generated in cold drawn pearlitic steel wires are analyzed. The aim is to find out the optimal conditions to be used in the design of a manufacturing process for obtaining more reliable structural components in terms of the main cause of failure: the hydrogen embrittlement (HE). To achieve this goal, diverse numerical simulations were performed by using finite elements (FE) and considering, on one hand, the first step of a real cold drawing chain, using (i) a conventional drawing die and (ii) modified drawing dies with different soft diameter reductions, and, on the other hand, numerical simulations by FE of the hydrogen diffusion assisted by stress and strain states to estimate the hydrogen distributions. Obtained results revealed the secondary reduction degree as a key parameter in the die design for reducing the drawing-induced residual stress. According to the results, low values of the reduction ratio cause radial distributions of residual stress with significant reductions at both the wire core and at the wire surface. In addition, the hydrogen accumulation at the prospective damage zone (near the wire surface) given by FE simulations is lower in the wires drawn with modified drawing dies including a skin pass zone.

Second Life for Plastic Fibre Waste Difficult to Recover: Partial Replacement of the Binder in Asphalt Concrete Mixtures by Dry Incorporation.

In previous studies, different additives and modifiers have been studied to improve the properties of asphalt concrete mixtures, whose main failures are plastic deformation and cracking. In this research, the improvement of the properties of asphalt concrete mixtures were investigated by introducing residual plastics as a substitute for virgin bitumen, which improves the sustainability of the mixtures. Furthermore, the results obtained from these new mixtures were compared with a mixture designed with polymer-modified bitumen (PMB). Ten experimental designs were tested with three types of waste fibre plastics from a municipal solid waste treatment plant and two percentages of bitumen replacement (15% and 25%). The experimental testing plan included air void characterization, moisture sensitivity, stiffness and fatigue resistance, among others. An increase of approximately 5% in voids could be observed when introducing the plastic material and therefore some tests were carried out to over-compact the specimens. The results showed an improvement in the mechanical performance of the experimental mixtures, highlighting the resistance against plastic deformations, which even reached similar values to the mixtures made with PMB.

Separation and mechanical properties of residual film and soil

In Xinjiang's perennial cotton (Gossypium hirsutum)-planting soil, the average residual amount of plastic film is as high as 265.3 kg/hm2, and the problem of pollution with residual plastic film in the tillage layer has become a major problem. To explore the mechanism of the separation of residual film and soil in the tillage layer and determine the conditions favorable for the separation of residual film-soil, this study established a constitutive model of residual film-soil contact based on the discrete element method and used the established constitutive model to simulate the process of separating residual film and soil. In addition, the influence of parameters, such as soil particle size and water content, on the force to separate the residual film and soil was studied using single factor and orthogonal experiments. The simulation results showed that the changing trend of the residual film-soil separation force curve did not differ much between the simulation and the actual comparison, and the curves were roughly the same. They all decreased after the separation force reached its peak value, but the simulated separation force curve was similar to that of the actual separation force. It increased rapidly from the beginning and reached peak separation force first. The single-factor experiment showed that the separation force of the used residual mulching film was higher than that of the unused mulching film. Under the same conditions, the maximum separation force required to separate the residual membrane was proportional to the positive pressure on the surface of the residual membrane and the size of soil particles. Under the same conditions, the maximum separation force required to separate the residual film is proportional to the positive pressure on the surface of the residual film and the size of soil particles. The maximum separation force decreased first and then increased as the soil moisture content increased. The results of the orthogonal experiment showed that the soil particle size had the greatest effect on the maximum separation force, followed by positive pressure on the residual film surface, soil moisture content, and the service life of mulch. In addition, film mulch that was buried 60 mm deep in the soil, a particle size of more than 2.5 mm, and a soil moisture content of 8% was the optimal combination of parameters to effectively separate the film mulching residue from the soil. Keywords: residual mulching film, soil, separation, discrete element simulation, sandy soil DOI: 10.25165/j.ijabe.20231601.7688 Citation: Ren Y, Guo W S, Wang X F, Hu C, Wang L, He X W, Xing J F. Separation and mechanical properties of residual film and soil. Int J Agric & Biol Eng, 2023; 16(1): 184–192.

Design and Test of Stripping and Impurity Removal Device for Spring-Tooth Residual Plastic Film Collector

The residual agricultural plastic film in China is not easily recovered due to the thinness and poor mechanical properties of domestic films, and a large amount of plastic film remaining in farmland soil poses a great threat to soil quality and crop production. A spring-tooth residual plastic film collector (SRPFC) is widely used in domestic residual plastic film (RPF) recycling operations. However, there are two major problems in the current SRPFC: the low recovery rate of the residual film (RRRF) caused by the difficulty of film-stripping and the high impurity rate in the film (IRF). In this paper, a stripping and impurity removal device (SIRD) is designed to address the existing problems of SRPFC, which is mainly composed of film-stripping tooth plates (FTP), two wind-collecting hoods, and two centrifugal fans. The motion and force analysis of the RPF in the film-stripping process was carried out, and the arc FTP was determined to be used for film-stripping. The size parameters of the FTP were obtained by establishing the coordinate system to solve the differential equation. By comparing and analyzing the force of RPF in the airflow field of the test bench for suspension speed and the airflow field of the wind-collecting hood, the RPF equivalent particle was established. The discrete phase model (DPM) in Fluent software was used to simulate the movement of the RPF equivalent particle, and the calculated air volume range of the centrifugal fan was 5501.88~6829.92 m3/h. The effects of forward speed, rotating speed of film conveying chain harrow (FCCH), and rotating speed of the centrifugal fan on RRRF and IRF were studied by orthogonal rotary combination experiment. The test results showed that the best combination of machine operation parameters was when the forward speed was 5 km/h, the rotating speed of the FCCH was 235 r/min, and the rotating speed of the centrifugal fan was 1978 r/min. Under these conditions, the RRRF was 92.53%, and the IRF was 9.31%. Field experiments were carried out with the rounded parameters, and the average RRRF was 92.07%, and the average IRF was 9.56% under the parameter combination, indicating that the optimization scheme of the device was feasible.