•The leaching kinetics of zinc residue is leached augmented with ultrasound is presented.•The best zinc recovery ratio can is showed at this paper.•The kinetics research of ultrasound-assisted ...leaching is researched using shrinking core model.•The rate controlling step of ultrasound-assisted leaching is identified to be the diffusion through the product layer.
The leaching kinetics of zinc residue, having total Zn content of 12.31%, along with other metallic components such as Fe and Pb, is leached using sulfuric acid as solvent, augmented with ultrasound is presented. The effects of variables such as the leaching temperature, sulfuric acid concentration, particle size, liquid/solid ratio and the ultrasound power have been assessed. The results show the maximum recovery of zinc to be 80% at an ultrasound power of 160W, leaching temperature of 65°C, sulfuric acid concentration of 1.4mol/L, particle size range of 74–89μm and liquid/solid ratio of 4. The kinetics of leaching is modeled using shrinking core model and the rate controlling step is identified to be the diffusion through the product layer. The raw and the leached residue are characterized using XRD and SEM/EDX analysis. The activation energy is estimated to be 6.57KJ/mol, while the order of reaction with respect to sulfuric acid concentration is 0.94 and particle size is 0.12 respectively.
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•Pyrolysis was applied to dispose plant residues obtained after phytoremediation.•Heavy metals could be stabilized in plant residues after pyrolysis.•Plant residues obtained after ...phytoremediation can be converted into biochar.•The generated biochar could be used as an effective sorbent for dye adsorption.
This study aimed to investigate the effect of pyrolysis on the stabilization of heavy metals in plant residues obtained after phytoremediation. Ramie residues, being collected after phytoremediation of metal contaminated sediments, were pyrolyzed at different temperatures (300–700 °C). Results indicated that pyrolysis was effective in the stabilization of Cd, Cr, Zn, Cu, and Pb in ramie residues by converting the acid-soluble fraction of metals into residual form and decreasing the TCLP-leachable metal contents. Meanwhile, the reutilization potential of using the pyrolysis products generated from ramie residues obtained after phytoremediation as sorbents was investigated. Adsorption experiments results revealed that the pyrolysis products presented excellent ability to adsorb methylene blue (MB) with a maximum adsorption capacity of 259.27 mg/g. This study demonstrated that pyrolysis could be used as an efficient alternative method for stabilizing heavy metals in plant residues obtained after phytoremediation, and their pyrolysis products could be reutilized for dye adsorption.
Our study was motivated by the large amount of crop residues produced in Brazil, which represent underutilized waste biomass and a serious threat to the environment because of the landfilling. For ...example, even though the corn crop is not popular in Brazil, it is produced in the area of around 18-20 million hectares with an average production of 5-6 t ha-1. That is the reason to seek for the crop residues value-added applications as proposed in the present study. Four Brazilian crop waste biomass: orange bagasse, corn husks, sugarcane straw and coffee residues were used for cellulose nanofibers (CNF) production. CNFs were prepared using alkali treatment, followed by bleaching with sodium chlorite and extraction with oxalic acid. All steps were applied under moderate conditions of temperature and pressure, such as temperature of 120 °C and below, water solutions with chemicals’ concentrations lower that 10% and short sonication pulses. CNFs with diameters in the range 50-70 nm were obtained and products from orange bagasse and corn husks presented high crystallinity indexes (CI), 0.72 and 0.75, respectively. The highest CNF yield was obtained from corn husks (38.5%) followed by sugarcane straw (24.0% with CI of 0.69). CNFs obtained from coffee residues showed a CI value of 0.65 after two bleaching steps. Different CNF morphologies were obtained according to the raw material. The four-crop waste biomass can be considered as excellent starting materials for CNF production in the four-steps process that adds new value to agro-industrial waste and might bring great economical valorization to Brazilian crops production.
Wetlands have been widely used in wastewater treatment and restoration of water bodies due to their ecological characteristics and functions. However, large amounts of plant residues are produced in ...wetlands every year and their treatment are facing large challenge. Synthesis of wetland plant-based functional materials (WPBFMs) has emerged as promising method for treating and recycling wetland plant residues. These functional materials have been demonstrated to effectively remove aqueous pollutants, such as antibiotics and dyes in wastewater. This article provides a comprehensive review on synthesis and application of WPBFMs for aqueous antibiotics removal and gives guidance for future research in treatment and recycling of wetland plant residues. It is shown that emergent plant residues are the mostly used raw materials for WPBFMs synthesis. The main products are biochar and its composites, cellulose and its modified materials, which are synthesized by slow pyrolysis and alkali treatment-bleaching treatment method, respectively. The removal pathways and mechanisms for aqueous antibiotics by WPBFMs are also discussed. Finally, the challenges and perspectives are discussed for synthesis and application of WPBFMs for antibiotics removal.
•We investigated the efficiency of agricultural wastes to remove heavy metals from aqueous solutions as single and competitive systems.•We examined the effect of chemical activation technique in ...order to enhance plant residues capacity for Ni removal.•Sorption of heavy metals was a function of pH and contact time.•The Langmuir and pseudo second order models well described the isotherm and kinetic of sorption of heavy metals respectively.•Determination of pHzpc of plant residues was useful parameter in describing sorption mechanism.•The native and modified plant residues used in present study had high capacity for removal of heavy metals from aqueous solutions.•The sorption mechanisms such as electrostatic attraction and ion exchange as well as complexation seem to be the most occurring phenomena.
In this research, the residues of sunflower, potato, canola, and walnut shell were used as sorbents to sorb heavy metals (Fe, Mn, Zn, Ni, Cu, and Cd) from aqueous solutions using batch experiments. The effect of pH and contact time was investigated. Maximum sorption of heavy metals by different sorbents was observed around pH 4–8. The optimal contact time was in the range of 20–600 min. The values of pHzpc (zero point of charge) measured for sunflower, potato, canola, and walnut shell residues were 6.06, 6.80, 6.15 and 5.85, respectively. The plant residues showed considerable capacity for removal of Fe, Mn, Zn, Cu, and Cd from aqueous solution but Ni sorption by residues was negligible. Chemical activation of sorbents with NaOH enhanced Ni sorption. Competitive sorption decreased the removal of heavy metals compared to the single system. The Langmuir isotherm model fitted well to experimental metals sorption. The sorption kinetic of heavy metals was described well by pseudo second order model. In our study, the sorption mechanisms such as electrostatic attraction and ion exchange as well as complexation seem to be the most occurring phenomena.
This figure indicates competitive sorption of six elements by different agricultural wastes. The simultaneous presence of metals in solution resulted in competition between different metal ions for sorption on the sorbent surface. The order of sorption of other metals (except Zn and Cd) was the same for sunflower and potato residues. The metals were not sorbed on the basis of Pauling (ionic radius) order. In a competitive system, the metals which were sorbed more than others by sunflower, potato, canola and walnut shell residue were Zn, Cd, Cd and Fe, respectively. Display omitted
The plant residues of tomato bring pressures to the environment and composting provides a feasible method to treat such agricultural waste. However, little is known about the succession and ...associations of the dominant lignocellulose degraders in the compost system. To further accelerate the process by inoculating key functional microorganisms, a compost pile composed of tomato stalk with maize straw addition was constructed, and the whole community structure and functions of the dominant were investigated by applying the integrated mata-omics. Results showed that Actinobacteria, Firmicutes, and Ascomycota dominated and drove the assembly of the co-occurrence network. In the thermophilic stage, Thermobifida was the exclusive degrader of cellulose, and Thermobifida fusca was the most important cellulolytic actinomycete. Saccharomonospora viridis, Planifilum fulgidum, Thermobacillus sp. and the dominant ascomycota of Aspergillus sclerotialis participated in hemicellulose decomposing. In the cooling phase, functional microorganisms became more diverse, with Nocardiopsis flavescens, Glycomyces artemisiae, Glycomyces sambucus, Streptomyces rubrolavendulae and Streptomyces vietnamensis joining the cellulose-degrading rank, and Chaetomium thermophilum emerging as the main hemicellulose degrader. More than two thirds of the bacteria-bacteria interactions and all the fungi-fungi associations were positive, while, both competition (for the same substrate of hemicellulose) and synergy (preference for cellulose and hemicellulose) coexisted in the bacteria-fungi interactions. In conclusion, these findings provide useful information for understanding the biodegradation of tomato plant residues better, and effects of the functional agents identified on composting process should be further studied.
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•Dominant lignocellulose degraders were identified by integrated meta-omics.•Thermobifida fusca dominated cellulose degrading in the thermophilic stage.•Functional entities and degrading enzymes diversified in the cooling phase.•Functional bacteria were both taxonomically and ecologically related.•Synergistic relationships among microorganisms enable the degradation efficiency.
In freshwater ecosystems, microplastics (MPs) are commonly found in reservoirs. However, limited information is available on the distribution of MPs in the reservoirs. In this study, we investigated ...the horizontal and vertical distribution characteristics of MPs in the Guanyingyan reservoir (the upper reaches of the Yangtze River, China) after impoundment and the influence of free-floating plant residues on the distribution of MPs. Results indicated that the MPs abundance in the horizontal distribution of the reservoir decreased significantly while the distance from the dam increased. The abundance of MPs in shoreline waters (average: 8.45 items L−1) was significantly higher than that in central waters (average: 4.80 items L−1). As for the vertical distribution, the percentages of fibers in the three water layers (surface, intermediate, and deep) have less variation when compared to other types of MPs. Besides, MPs who are less than 0.5 mm in size are the majority. With deeper underwater, there would be more MPs with particles smaller than 200 μm in size. At the same time, there would be fewer MPs with particles ranging from 200 to 500 μm in size. PS, PP, and PE are the main polymer types of surface water, while PVC, PE, and PET are the common type in deep water. In shoreline water, the dry weight of floating plant residues showed a positive correlation with microplastic abundance in different layers. As above said, this study confirmed that MPs in reservoirs after impoundment would tend to accumulate in the front section of the reservoir and the shoreline water. Besides, free-floating plant residues would accumulate in reservoirs, resulting in the sinking of MPs.
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•Dam reservoirs are potential enrichment zones for MPs.•Microplastics accumulate in the shoreline waters of a reservoir.•PS, PP, and PE are the most frequent MPs types found on the surface of a reservoir.•Free-floating plant residues in reservoirs lead to an accumulation of MPs.
No-tillage (NT) is an alternative technique adopted in cassava (Manihot esculenta Crantz) growing areas to reduce soil loss. However, it may affect the development of storage roots depending on the ...soil-covering residues. This study evaluated the soil and water losses and storage root yield and quality of cassava planted in the dry and rainy seasons using conventional tillage (CT) and NT, following sole maize (Zea mays L.) cropping or maize–palisadegrass Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster intercropping. The experimental design was a randomized block with five replications. Four treatments were considered representing cassava planted using CT and NT following sole maize or maize–palisadegrass intercropping. CT caused soil loss of up to 43.4 Mg ha−1 over the 16 months of cassava cultivation. NT following maize–palisadegrass intercropping did not decrease cassava yield nor its quality and reduced both soil and water losses. In the rainy planting season, NT reduced soil loss by up to 80% (35 Mg ha−1), while in the dry planting season, the reduction varied between 28% and 38% (8–11 Mg ha−1). These findings suggest that previous maize–palisadegrass intercropping followed by NT of cassava is recommended for increasing soil conservation, especially in cassava planted in the rainy season.
•For cassava planted with conventional tillage (CT), soil loss reaches 43.4 Mg ha−1.•In the rainy season, soil loss in the CT is 1.46-fold greater than in the dry season.•No-tillage reduces soil losses by 80% in cassava planted in the rainy season.•Cassava root, starch, and flour yield is not affected by no-tillage.
Microbial immobilization of nitrate (NO3−-N, INO3), which represents a major nitrogen (N) retention mechanism, is carbon (C)-limited in soils. Our previous study has demonstrated that soil INO3 can ...be enhanced with the addition of simple organic C at rates >500 mg C kg−1, or complex organic C with C/N ratios >18. However, whether the quantity and quality of organic amendments can be used to quantify soil INO3 remains elusive. We hypothesized that soil INO3 rate increases with an increase in both organic C application rate and amount of a particular organic C component of added organic materials. Using the organic 15N recovery method, following the application of seven organic C sources at a gradient of 0, 1, 2, and 5 g C kg−1, we demonstrated that soil INO3 rate increased linearly with an increase in organic C application rate across different organic C types that can stimulate INO3. In addition, soil INO3 rates, expressed as mg N per g C applied increased logarithmically with an increase in holocellulose (cellulose + hemicellulose) content in the organic amendments. Our structural equation modeling, for the first time, suggest that holocellulose drives soil INO3 rate by influencing bacterial abundance at the highest organic C application rate. The results could enhance our capacity to predict soil INO3 trends.
•Soil INO3 increased with increasing carbon application rate.•Soil INO3 increased with increasing holocellulose content in organic amendment.•Holocellulose drove INO3 via influencing soil bacterial abundance.
Globally, substantial quantities of organic amendments (OAs) such as plant residues (3.8×109Mg/yr), biosolids (10×107Mg/yr), and animal manures (7×109Mg/yr) are produced. Recycling these OAs in ...agriculture possesses several advantages such as improving plant growth, yield, soil carbon content, and microbial biomass and activity. Nevertheless, OA applications hold some disadvantages such as nutrient eutrophication and greenhouse gas (GHG) emission. Agriculture sector plays a vital role in GHG emission (carbon dioxide— CO2, methane— CH4, and nitrous oxide— N2O). Though CH4 and N2O are emitted in less quantity than CO2, they are 21 and 310 times more powerful in global warming potential, respectively. Although there have been reviews on the role of mineral fertilizer application on GHG emission, there has been no comprehensive review on the effect of OA application on GHG emission in agricultural soils. The review starts with the quantification of various OAs used in agriculture that include manures, biosolids, and crop residues along with their role in improving soil health. Then, it discusses four major OA induced-GHG emission processes (i.e., priming effect, methanogenesis, nitrification, and denitrification) by highlighting the impact of OA application on GHG emission from soil. For example, globally 10×107Mg biosolids are produced annually which can result in the potential emission of 530Gg of CH4 and 60Gg of N2O. The article then aims to highlight the soil, climatic, and OA factors affecting OA induced-GHG emission and the management practices to mitigate the emission. This review emphasizes the future research needs in relation to nitrogen and carbon dynamics in soil to broaden the use of OAs in agriculture to maintain soil health with minimum impact on GHG emission from agriculture.
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► A comprehensive overview for the first time on GHG emission from organic amendments (OAs) ► The amounts of OAs and their carbon and nutrient value are quantified. ► The potential volumes of GHG produced from land application of OAs are quantified. ► The processes by which GHGs are emitted from soil are described. ► Management strategies to mitigate GHG emission from OAs are discussed.
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