De-inking Paper Sludge Research Articles

Texture and Contamination-Level Dependent Effects of Calcium-Rich Deinking Paper Sludge Biochar on Soil Cd Availability, Enzymatic Activity, and Plant Stress Mitigation

The study evaluated calcium-rich deinking paper sludge (DPS) biochar's capability as a viable alternative method to mitigate soil cadmium (Cd) availability. Our analysis of 68 recent studies showed that 75% of the studies focused on contamination levels below 10 mg kg-1. However, mining and smelting areas exhibit higher levels of Cd contamination (mean value of 57.5 mg kg-1 with a CV of 128%), necessitating a contamination rate-dependent approach.Clay loam (CL) and sandy loam (SL) soils were artificially contaminated with Cd to mimic polluted areas (20, 40, 80 mg kg-1). Soils were aged for six months and then treated with DPS biochar doses of 0%, 1%, and 3% (w/w) for a month. Cd extractability and toxicity were gauged using diethylenetriaminepentaacetic acid extraction and plant physiology tests. Supplementarily, machine learning algorithms were tested to predict plant physiological parameters and biomass production, leveraging variables from principal component analysis and design parameters.Biochar application (3%, w/w) reduced soil Cd availability (20.1% in SL, 8.4% in CL; p < .05), attributed to increased soil pH, enhanced microbial activity, and expanded soil surface area. The plants grown in treated soils displayed increased dry matter content, chlorophyll, relative water content, and decreased malondialdehyde levels. The impact varied, being more pronounced in SL soils with high Cd contamination.This study presents the first report on the use of DPS biochar in Cd-contaminated soils and sets expectations for its outcomes regarding plant physiology and soil microbial activity in a diversified experimental design. DPS biochar appeared as a tool for mitigating soil Cd availability and alleviating plant stress particularly in SL soils. The biochar's efficiency was influenced by its dose, the level of contamination, and the soil type, highlighting the importance of tailored application strategies.

Evaluating the properties of deinking paper sludge from the Mediterranean area for recycling in local areas as a soil amendment and to enhance growth substrates

AbstractRecycling of paper generates large quantities of paper sludge that is rich in organic matter and can be exploited to counteract organic matter loss in agricultural soils, especially in some geographical areas, such as the Mediterranean. In order for deinking paper sludge (DPS) to be recycled, chemical and physical characterizations are required along with an analysis of possible contaminants. DPS from Italy and Tunisia, resulting from various deinking processes, were analyzed and compared in terms of their chemical properties (pH, OM, total N, C/N ratio, mineral nutrients, and trace metals), surface chemistry [diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and Fourier-transform infrared (FTIR) spectroscopy], and thermal stability [thermogravimetric analysis (TGA)]. The aim was to improve their use as amendments in soils or growth substrates. Elemental analysis revealed higher carbon concentrations in the Tunisian DPS and similar nitrogen contents, high mineral nutrient levels, and potentially toxic trace element levels below the limits allowed for soil amendment. No evidence was found for the presence of organic pollutants, pathogens, or toxic heavy metals. Surface chemical analysis revealed comparable materials rich in aromatic, phenolic, aliphatic, and polysaccharide structures along with clay minerals and carbonates. The thermal analysis revealed similar decomposition temperatures for the organic matter. Practical implications of the results are discussed, highlighting the similar properties of sludge following ink removal by different processes and the need to integrate the N content in order to be able to employ sludge as an amendment in soil and growing media. Given the similarity of the compositions of the materials, appropriate DPS management is key to improving soil fertility, reducing paper waste disposal, and implementing a circular economy in the Mediterranean, where climate change is having a significant impact.

Utilizing de‐inked paper sludge for sustainable production of medium‐density fiberboard: A comprehensive study

AbstractThis study investigated converting abundant paper mill waste, de‐inked paper sludge (DPS), into value‐added medium‐density fiberboard (MDF) panels. The objective was to repurpose this solid waste into a valuable material that aligns with the principles of a circular economy. Previous research has examined the addition of paper sludge to wood composites, but there is limited information on the specific incorporation of DPS into MDF production. This investigation offers new insights into this application. MDF panels were manufactured using hardwood fibers, with varying levels of urea‐formaldehyde resin (10% and 12% by weight) and different loadings of DPS (ranging from 0% to 50% by weight). X‐ray diffraction analysis revealed the presence of defective DPS fiber crystals. Contact angle measurements confirmed that DPS had poor wettability, corresponding to increased water absorption. As more DPS was incorporated, the mechanical properties of the panels progressively weakened due to defective fibers and poor adhesion between the fibers and the matrix. This was evident in scanning electron microscopy micrographs, which showed an escalation in interfacial flaws. Increasing the resin dosage noticeably improved the internal bond strength and reduced moisture uptake across all levels of DPS. However, at a DPS loading of 50%, the properties of the panels deteriorated by 36%–57% compared to the control MDF. Additionally, thickness swelling and water absorption increased significantly with higher DPS content, primarily due to the hydrophilic nature of the fibers. Based on optimization, it was determined that a DPS loading of 20% with a resin content of 12% provided the best balance between performance, waste utilization, cost, and moisture resistance. The reuse of abundant paper sludge supports the goals of a circular economy. However, strategies are required to tailor the processing methods and enable higher levels of recycled material without excessively compromising the key attributes of the product. Further research should focus on enhancing the quality of DPS and its compatibility with wood fibers and resin to enhance the performance of the composite material.Highlights DPS from recycled paper mill assessed for MDF production with wood fibers and resin Increasing DPS loading caused reductions in strength and adhesion of panels Water absorption and thickness swelling markedly rose with more DPS addition It was attributed to hydrophilic fibers and disrupted fiber‐matrix bonding Optimal formulation was 20% DPS loading and 12% resin content, balancing performance, waste utilization, and cost.

Industrial deinking paper sludge waste: toxicity risk and health effects assessment of heavy metals by USEtox model

Disposal of waste sludges produced in large amounts in the paper industry could generate significant environmental and health issues. One strategy to address them involves revalorization of deinking paper sludge (DPS) by reusing it as fertilizer. However, the possible human health risks associated with the use of DPS are still not well explored. The main objective of this report was to estimate DPS impacts on human toxicity. To achieve this goal, heavy metals analysis of the DPS waste (Cadmium; Cd, Copper; Cu; Molybdenum; Mo, Manganese; Mn; Lead; Pb; Cobalt; Co) was conducted. The assessment of human toxicity was performed by applying the UNEP/SETAC toxicity model USEtox 2.0 to establish indicators that reflect the potential health damage of these chemicals when released into the environment. Laboratory analysis, revealed a very low concentration of the DPS by the metallic contaminants (Cd, Cu, Mo, Mn, Pb, Co). According to the USEtox model results, these quantities will not lead to either carcinogenic or non-carcinogenic risks on human health even if there is a use of very high quantities of DPS. Indeed, the number of cases /t DPS emitted in agricultural soils didn’t exceed 950.10-7 for the non-carcinogenic effect and 3.71.10-7 for the carcinogenic effect for Pb. For Mn and Co, we noticed no toxic effects (0 cases /t DPS emitted). Furthermore, we observed that Mo and Cu had very weak non-carcinogenic effects and led respectively to 445.10-7 and 56.10-7 cases /t DPS emitted. Regarding the effect of Cd toxicity, in order to have one case of this metal toxicity from DPS waste in our study, we had to use a very important quantity of DPS (≈ 2 821 680t). All these data emphasized on the absence of heath human toxicity risk after DPS waste industrial disposal, by ingestion or inhalation.

Assessment of Earthworm Viability and Soil Health after Two Years of Raw and Composted De-Inking Paper Sludge Amendment

The improvement of soil fertility properties is a priority for meeting sustainable development goals and world food security. One potential benefit of using paper sludge in agriculture is the reduction of waste and associated environmental impacts. By using paper sludge as a soil amendment, it is possible to divert away this material from landfills and instead use it to improve soil fertility and support the growth of crops. However, it is important to note that paper sludge may contain contaminants harmful to plants and soil health, of which earthworm viability serves as a key indicator. The present investigation aimed to evaluate changes in soil properties after the application of raw and composted de-inking paper sludge for two years. Accordingly, a field study was conducted in Manouba, a semi-arid region of Tunisia with a clay loam soil. The raw de-inking sludge (DS) and composted de-inking paper sludge (DSC) were applied at 30 and 60 t ha−1 and 20 and 40 t ha−1, respectively. Soil treatments were compared to unamended soils (C), to determine the optimal sludge treatment and rate for increasing the soil quality. Soil chemical (soil organic matter SOM, total carbon TC, and nitrogen TN, nutrient soil contents organic matter fractioned), physical (porosity and structural stability), and biological parameters (earthworms viability) were assessed. The results showed an increase of soil OM in the DS and DSC amended soils with the lowest rates (30 and 20 t ha−1). The humic fraction was found to be the dominant form. TC and TN were improved in the DS and DSC amended soils with the highest rates: 60 (DS2) and 40 t ha−1 (DSC2). Phosphorus and potassium were also increased in a dose-dependent manner. However, the soil porosity decreased in all treatments. The composted de-inking sludge was toxic for epigeic species, which could be explained by the use of litter while composting. Overall, the application of DS and DSC at low rates (30 and 20 t ha−1, respectively) might be a promising alternative for improving soil quality and at the same time ensuring the proper management of these wastes.

The suitability of de-inked paper sludge as growing media amendment for ornamental potting plants

The suitability of de-inked paper sludge as growing media amendment for ornamental potting plants

Valorized deinking paper residue as fill material for geotechnical structures

This study introduces a novel geotechnical composite material comprising two types of fill material sourced from the paper industry—deinking paper sludge ash (DPSA) and deinking paper sludge (DPS). Five composites with different DPSA and DPS contents were investigated. Two composites were selected for further analyses. The technology and procedure for composite installation were implemented in field tests. The composites with 80% and 70% DPSA exhibited the elasticity required to withstand minor landslide slip deformations, in addition to achieving sufficiently high values of uniaxial compressive strength. The composites had a low maximum dry density value, which led to fewer settlements in the entire support structure. The enhanced shear characteristics can enable the construction of a thinner retaining wall. The delay between preparation and installation of the composites was further investigated. The field tests confirmed that the composites with 80% and 70% DPSA can be installed on the construction site 4 h and even 24 h after mixing. In 2018, a retaining wall structure with 70% DPSA and 30% DPS was successfully implemented near a railway line using conventional technology as followed-up research to the herein presented study. Results have been derived from work performed in the scope of the H2020 Paperchain project in which novel circular economy models centered on the valorization of the waste streams generated by the pulp and paper industry as secondary raw material for several resource-intensive sectors, including the construction sector, have been developed. Environmental benefits are savings in natural raw materials, reduction of landfill disposal as well as CO2 emission reduction.

Short-Term Effects of Biosolid Application on Two Mediterranean Agricultural Soils and Durum Wheat Yield

This study evaluated the effects of de-inking paper sludge (DPS) and sewage sludge (SS) application on soil properties, and durum wheat growth and yield. A pot experiment was performed on Calcaric cambisol (clCM) and Cromic Luvisol (coLV) soils. Three DPS rates (0, 30, and 60 Mg ha−1) were studied with and without nitrogen fertilizer (280 kg NH4NO3 ha−1). DPS was also mixed with SS at two rates (5 and 10 Mg ha−1) to highlight the benefits of organic nitrogen compared to mineral nitrogen. DPS improved total organic carbon and nitrogen, mineral nitrogen, and soils cation exchange capacity, the 30% rate provided the greatest improvement in both soils. DPS increased grain and root P, K, Ca, and Mg contents in both soils. It also increased wheat straw N, P, Mg, and Ca for the same soil compared to the control. Mixed DPS treatments with nitrogen fertilizer enhanced grain yield by up to 38% and increased root biomass in the studied soils. Thus, DPS is a potential source of organic matter and a liming agent for acid soils when appropriate supplemental fertilizer is provided.

Leaching test for assessing compliance with environmental requirements of fired clay bricks incorporated by deinking paper sludge

The deinking paper sludge (DPS) generated by paper recycling incorporated in ceramic pastes has received significant attention to develop environmentally-friendly construction materials with a good thermal and sound insulation characteristic while maintaining a resistance mechanical acceptable by standards. The environmental risks associated with the incorporation of these sludge into clay bricks that rich in heavy metals such as Cr, Pb, Zn, Cu, Ni, etc. have been evaluated. The evaluation of these metals was carried out by performing the leaching test in order to be able to introduce this new material in the list of materials to be marketed in the field of civil engineering. Leaching tests were performed on clay, DPS and the finished product as fired bricks. Leaching results on clays show that they are non-hazardous products, while heavy metal leaching of DPS is above the limiting concentrations, which classifies DPS as a hazardous waste. In contrast, the leaching concentrations of the bricks incorporated by DPS, show that the heavy metals were immobilized in the ceramic structures of all the fired bricks. In this study, the percentages of DPS added in the composition of the bricks are 8%, 10% and 12%. Results of leaching test suggest that replacing up to 12% of clays with DPS can provide bricks to reduce the environmental impact of abundant waste and preserve non-renewable natural resources.

De-inked paper sludge and mature compost as high-value components of soilless substrate to support tree growth

Abstract The recycled paper industry produces tons of waste whose disposal is a cost for industry and the environment. This research examines the suitability of de-inked paper sludge (DPS), after pelletization, as a sustainable alternative component to a peat-based growing media, creating ideal root conditions for tree development (e.g. high water storage, low compaction). DPS, tested on Lepidium sativum L. germination, did not show toxicity effects. Three species, Quercus ilex L., Lagerstroemia indica L. and Prunus serrulata “Kanzan”, were planted in 40 cm O pots filled with a control (peat, pumice and zeolite) and the experimental substrate (compost, DPS pellets, pumice and zeolite). After two years in the nursery, the trees were planted in situ. The physical and chemical properties of substrates were analyzed. Plant morphological and physiological parameters were monitored: trunk diameter, leaf dry matter, leaf nitrogen, chlorophyll, and photosynthetic efficiency. The new substrate showed higher Corg (+135%), total N (+73%) and easily available water (+19%), compared to the control substrate used in the nursery. In this new substrate, the trees showed similar radial growth values to the control in the nursery and after transplanting in situ improved their photosynthetic performance in terms of quantum yield of photosystem II (+36%, and +29% in P. serrulata and L. indica, respectively) and electron transport rate (+39%, +25%, and +32% in P. serrulata, Q. ilex and L. indica, respectively). Pelletization represents an attractive amendment for growing media, which enhances the plant’s physiological health status. This study proposes alternative recovery methods for paper industry waste with low environmental impact. As the process is developed locally, it should also contribute to reducing energy-related CO2 emissions from transport. Pelletization represents an attractive novelty in the use of DPS as amendment for growing media, which enhances the plant’s physiological health status. This study proposes alternative recovery methods for paper industry waste with low environmental impact. As the process is developed locally, it should also contribute to reducing energy-related CO2 emissions from transport.

Mitigation of CO2, CH4 and N2O from Acidic Clayey Soil Amended with Fertilizer Pellets Based on Alkaline Organic Residues

Alkaline organic residues, such as wood ash (WA), deinking paper sludge (DPS), and mixed paper sludge (MPS) could have a significant potential for mitigating greenhouse gases (GHG) when they are used for land application. The DPS was mixed and then granulated with MPS, WA and/or composted DPS to form pellets. A 56-d incubation study was carried out to investigate the effect of alkaline organic residue pellets on: (1) the biological and chemical properties of acidic clayey soil; (2) on carbon dioxide (CO2), on methane (CH4), and nitrous oxide (N2O) soil emissions. The experimental design included eight different treatments: unfertilized control (Control), fertilized control with mineral nitrogen (controlF), and six pelleted alkaline organic residue amendments (T1–T6) combined with mineral nitrogen fertilizer. The six amendments were: (T1) 100% DPS; (T2) 100% composted [50% poultry manure and 50% T1]; (T3) 50%WA + 50% T1; (T4) 50% WA + 50% T2; (T5) 50%T2 + 30%WA + 20% MPS; (T6) 50% T1 + 30%WA + 20% MPS. The results showed that alkaline residues significantly increased soil pH, the concentration of water-extractable organic carbon, and water-extractable nitrogen. Alkaline treatments had a positive effect on soil microbial activity. The highest mitigation efficiency of cumulative CO2 was obtained with T4, which released 10% less CO2 than other treatments. No significant effect on cumulative CH4 emissions was observed. Total cumulative N2O emissions were reduced by 37% with T5. Our study also showed that organic pellets based on alkaline residues improved the soil properties and can play a role in the mitigation of GHG in acidic clayey soil. Therefore, the co-application of alkaline organic residue pellets with chemical fertilizer might be considered as a sustainable approach in agriculture.

Nitrogen and phosphorus release from paper mill biosolids as affected by material source and soil type under controlled incubation

Combined paper mill biosolids (PB) are a well-known fertilizing source of nitrogen (N) and phosphorus (P). Many jurisdictions have established default values for estimating their agronomic N and P contribution, but nutrient release can vary with their chemical properties, and this has been little studied. The objective of this incubation study was to compare four PB of different sources along with a de-inking paper sludge (DPS) for their N and P release in three contrasting soils under controlled conditions (25 °C, 60% water-filled pore space). Treatments consisted of PB or DPS at 50 Mg fresh mass ha−1, PB at 30 Mg fresh mass ha−1 plus inorganic N to supply 100 kg available N ha−1, inorganic NP fertilizer, and an unfertilized control. Measurements of NO3 + NH4-N were made after 3 d and 1, 2, 3, 4, 6, 8, 12, and 16 wk of incubation. Mehlich-3 P was measured after 2 and 16 wk of incubation. Nitrogen mineralization generally declined a few days after PB addition and then gradually and constantly increased. The P mineralization of PB also increased with time. By the end of incubation, net N and P release averaged 30% (7%–49%) and 75% (16%–116%) of the NP fertilizer, respectively. The intensity of release, however, varied with material characteristics and soil type. Mineral N addition to the 30 Mg PB ha−1 promoted N release to a level comparable to NP fertilizer. Soil N immobilization occurred with the DPS application. Current default N value used for PB in Quebec and Ontario is appropriate but not P.

CO2 Emission and Change in the Fertility Parameters of a Calcareous Soil Following Annual Applications of Deinking Paper Sludge (The Case of Tunisia)

The use of deinking paper sludge (DPS) as a fertilizer instead of sending it to landfill could play a role in reducing greenhouse gases and improving soil properties. The objectives of this study were (1) to evaluate the changes in the physical (permeability and structural stability), chemical (particularly soil pH), and biological (microbial metabolic quotient (qCO2), microbial biomass soil CO2 emissions) of a calcareous agricultural soil following two successive annual amendments with three treatments (0, 30, and 60 Mg DPS ha−1—control, DPS30, and DPS60, respectively); and (2) to determine whether the addition of N-fertilizer to these treatments (controlF, DPS30F, and DPS60F, respectively) causes changes to soil fertility. The DPS application increased soil organic matter (+0.80%: DPS60 vs. control; and +0.35%: controlF vs. DPS60F), available phosphorus (+23.14 mg kg−1: DPS60 vs. control; and +14.34 mg kg−1: DPS60F vs. controlF), potassium (+0.6 g kg−1: controlF vs. DPS30F), and calcium (+0.28 g kg−1: DPS60 vs. control). The 60 Mg DPS ha−1 rate improved permeability and structural stability, regardless of the presence or absence of N-fertilizer. On the other hand, the 60 Mg DPS ha−1 rate without N-fertilizer lead to a decrease in total mineralization rate and qCO2, thereby indicating a reduction in CO2 emissions. The rate of 60 Mg ha−1 DPS could be effectively used to enhance the permeability and stability (soil restoration) and mitigate CO2 emissions, whereas the 30 Mg ha−1 rate could be used as fertilizer to improve the fertility of calcareous soils.

Alternative Filler Recovery from Paper Waste Stream

The study is a first investigation of the feasibility to preserve recycled fillers (e.g. calcium carbonate, kaolin) from deinking paper sludge for newspaper production using an alternative approach respect to the actual methods. Deinking paper sludge was incinerated at 575 °C. The thermal stability of the incinerated sludge (ash) was evaluated by infrared analysis. Subsequently, the resulting ash was bleached by sodium dithionite. The particle size of the ashes was analysed by laser diffraction. The effect of recycled fillers on recycled paper pulp, after blending, was evaluated by the analysis of the physical and optical properties of the obtained paper sheets. Analysis showed the conservation of the calcium carbonate and other fillers’ molecular structure, both after incineration of the sludge and after bleaching. The dithionite treatment of the ashes resulted in ISO brightness levels of more than 70. The brightness was stable over one month. Paper sheets made by blending the bleached ashes with recycled paper showed an improvement of brightness and opacity but a decrease in terms of porosity and breaking length compared to paper sheets made without any filler. The proposed method still requires further studies to evaluate the economical application but offers an opportunity for the recycling of inorganic materials and valorisation of the sludge.

Deinking sludge compost stability and maturity assessment using Fourier transform infrared spectroscopy and thermal analysis.

Thermal composting is an important and useful way to transfer raw organic matter into value-added product rich in humic substances. Furthermore, thermal composting is a very promising way to reduce deinking paper sludge pollutions, which are difficult to remove. The objective of this study was to investigate the behaviour of the composting process of deinking paper sludge with poultry manure over 14 months. Two composts were used: C1 (70/30: deinking paper sludge/poultry manure) and C2 (50/50: deinking paper sludge/poultry manure). The compost stability and maturity were assessed via physico-chemical and thermal analyses: thermogravimetric analysis, differential thermal analysis and diffuse reflectance infrared Fourier transform spectroscopy. Diffuse reflectance infrared Fourier transform spectroscopy analysis provided chemical information for the presence of aromatic, phenolic, aliphatic and polysaccharidic structures. Thermogravimetry analyses revealed that both deinking paper sludge composts were rich in humic acids. The ratio E4/E6 (fulvic acids/humic acids) was also carried out to characterise the maturity index of composts. After 14 months, the compost C2 is more stable, mature and rich in humic acids than compost C1. Furthermore, the addition of poultry manure to the deinking paper sludge-based composts enhanced the formation of humic substances. From 0 to 14 months of composting, the concentration of polychlorinated biphenyls decreased from 0.2 to 0.1 mg kg-1 and from 0.6 to 0.2 mg kg-1 for C1 and C2, respectively.

Lignocellulosic waste fibers and their application as a component of urea-formaldehyde adhesive composition in the manufacture of plywood

This research uses lignocellulosic waste fibers from the fiberboard industry, pulp and paper mills for their effective processing to reduce waste discharge, preserve the ecological environment, and produce innovative and sustainable solutions. The effects of using waste fibers obtained from fiberboard wet process, recycled paper process, and cellulose process as adhesive additives on some physical and mechanical properties and formaldehyde emission of adhesives and plywood panels were examined. Three major types of fibers, primary fibrous sludge (PFS), primary cellulose sludge (PCS), and deinked paper sludge (DPS) were characterized and evaluated as adhesive fillers in plywood manufacturing. UF adhesive filled with 15 wt% wheat flour (WF) was used as a reference sample. Plywood panels were made of formulations with urea-formaldehyde (UF) resin filled with three different concentrations of fibers, 1 wt%, 3 wt%, and 5 wt%. Compared with DPS and PCS, PFS had a higher lignin and extractives content, and lower pH. These characteristics make PFS a better adhesive filler for plywood than DPS or PCS. Panels with UF/PFS, UF/DPS and UF/PCS formulations at a sludge content of 1–5 wt%, 1 wt% and 3 wt%, respectively had higher wet shear strengths than those made with the control sample. It was also found that the use of fibers obtained from different processes in the UF adhesive composition decreased the formaldehyde emission of panels. The PFS, PCS, and DPS reduced formaldehyde emissions by up to 27.8, 24.9, and 19.4%, respectively compared with control panels, without compromising the shear strength. The shear strength of plywood panels with all investigated sludges met the requirements of the EN 314-2 standard.

Synergetic effect of Posidonia oceanica fibres and deinking paper sludge on the thermo-mechanical properties of high density polyethylene composites

This study evaluated the reinforcement potential of Posidonia oceanica fibres (POF) and deinking paper sludge (DPS) on the thermo-mechanical properties of high density polyethylene (HDPE) binary and hybrid composites. The weight ratios of the fillers (POF and/or DPS) to the polymer were 0:100; 20:80; 30:70 and 40:60 (wt:wt). Maleated polyethylene (MAPE) was added at a proportion of 3% by weight. The chemical composition, structural and thermal properties and morphology of the fillers were investigated by Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The mechanical (tensile and impact strength) and thermal properties (TGA and Differential Scanning Calorimetry (DSC)) of the binary and hybrid composites were also investigated. Binary and hybrid composite properties depend on the chemical composition of the fillers (POF and DPS), the filler/matrix interfacial adhesion and the POF: DPS ratio. The tensile modulus and strength of the binary and hybrid composites increased with increasing filler content (POF or/and DPS). A better interfacial adhesion between fillers and matrix was achieved in the presence of MAPE. HDPE/POF/MAPE composites achieved the highest tensile modulus and strength with 40% POF. But lower thermal stability, ductility and impact strength were found with the addition of the POF. However, the thermal stability, crystallinity, ductility and toughness improved in HDPE/POF/DPS/MAPE hybrid composites due to the addition of DPS or the substitution of POF by DPS.

Synergic use of chemical and ecotoxicological tools for evaluating multi-contaminated soils amended with iron oxides-rich materials

Abandoned waste piles from ancient mining activities are potential hot spots for the pollution of the surrounding areas. A pot experiment was carried out to check the potential toxicity of the dumping material present in one of these scenarios, and several amendments were tested to attenuate the spread of the contamination events. The waste material had an acid pH and a large total concentration of As and Cu. A dose-response experiment was performed with this material following OCDE 208 test. A proportion 90:10 uncontaminated soil: dumping material (% w/w) was selected for the following experiment, in order to surpass the amount of dumping material that caused 50% reduction in plant growth. Pots were filled with the 90:10 mixture, planted with seeds of Brassica napus and amended with the following materials: three iron oxides of Bayoxide® E33 series, iron (II) sulphate in combination with de-inking paper sludge (Fe+PS), iron oxide-rich rolling mill scale (ROL) and iron oxide-rich cement waste (CEM). Amendment effectiveness evaluation was based on chemical and biological assays: extractable trace element concentration, soil enzymatic activities, inhibition of light emission of V. fischeri and Anabaena sp., B. napus L. fresh weight and screening test for emergence of B. napus L. seedlings. Amendments E33HCF and Fe+PS were the most effective in reducing extractable As and Zn concentration. B. napus weight and dehydrogenase and β-glucosidase activities were positively increased with the two above mentioned treatments but they triggered more toxic effects for V. fischeri luminescence. E33P treatment was the only in which the EC50 was higher than in the control. Anabaena sp. was less sensitive than V. fischeri as its luminescence was not hampered by any treatment. Trace element concentration did not significantly affect the failure in seed emergence. E33HCF and Fe+PS could act as proper amendments as they decreased extractable As and Zn. Further, plant fresh weight, enzymatic activities and some of the bioassays identified the latter treatments as the best ones among those tested here to this type of multi-contaminated soil.

Effect of High Content of Deinking Paper Sludge (DPS) on the Reinforcement of HDPE

Deinking paper sludge (DPS)/high density polyethylene (HDPE) composites with and without coupling agent (3 % of maleated polyethylene (MAPE)) were manufactured by twin-screw extrusion followed by injection molding with high percentages of DPS (0, 20, 30 and 40 %). The effects of DPS content and MAPE on the mechanical, thermal, and morphological properties of the DPS/HDPE composites were investigated. Increasing DPS content in composites increased the tensile and flexural modulus (E; MOE), tensile and flexural strength (Rm; MOR), while decreased elongation at break and Un-notched impact resistance due to a poor adhesion between the DPS and HDPE. The addition of DPS also improved the thermal stability and increased the composites crystallinity. High content of DPS (40 %) and 3 % MAPE achieved good interfacial adhesion between fibres of DPS and HDPE. Therefore, an increase is observed for Rm, MOR, ductility, and impact toughness.

Biochar from Pyrolysis of Deinking Paper Sludge and Its Use in the Remediation of Zn‐polluted Soils

AbstractAn increasing proportion of recycled fibres are used in paper industries. Removing the ink, clay, coatings and contaminants from paper waste in order to produce recycled fibres creates large amounts of deinking paper sludges. The preparation of biochar from pyrolysis of this waste and its use in soil remediation contaminated with heavy metals could be an interesting valorization alternative. Our aim was to study the influence of biochar from deinking paper sludge (HP) pyrolysis in the treatment of Zn‐polluted soils. Three different soils contaminated with 2000 mg Zn kg−1 were amended at a rate of 10% with deinking paper sludge and deinking paper sludge biochar prepared at three different temperatures (300, 400 and 500 °C). Soils were incubated under laboratory conditions, and soluble Zn was measured. The addition of biochar reduced the amount of mobile Zn. Finally, Zn solubility decrease was more pronounced for biochars prepared at a higher temperature. Copyright © 2016 John Wiley &amp; Sons, Ltd.