Trace chemical partitioning in construction and demolition debris fines: process and market implications

Construction and demolition debris (CDD) fines, a residue generated from mechanized CDD recycling, can often be beneficially reused. Concentrations of chemicals of potential concern in CDD fines should be evaluated prior to being reintroduced into the environment to assess risk and make informed decisions about appropriate reuse opportunities. The distribution of trace chemicals in CDD fines as a function of particle size was measured to evaluate if concentrations in the bulk material can be reduced by removing certain particle size ranges through screening. Chemicals of potential concern, including arsenic, lead, sulfate and polycyclic aromatic hydrocarbons (PAH), were characterized in four different size fractions (19–4.8 mm, 4.8–0.84 mm, 0.84–0.3 mm, < 0.3 mm) of CDD fine samples collected from 12 US CDD recycling facilities throughout the US. Results revealed that aluminum, arsenic and chromium concentrations were distributed evenly throughout all four size fractions. As for the remaining chemicals, most samples had lower concentrations in the 19–4.8 mm size range. In some samples and for certain chemicals, removal of the finer size fractions reduced overall concentrations in CDD fines, suggesting that additional processing may be worth further investigation.     

Effect of Gamma Radiation on the Properties of Crosslinked Chitosan Nano-composite Film

Chitosan nano-composite film crosslinked by citric acid and with glycerol as plasticizer and MgO as antibacterial agent was prepared by casting method. MgO nanoparticles were synthesized via calcination method in furnace at 500 °C for 4 h and characterized by X-ray diffraction and transmission electron microscope. The chitosan nano-composite film with composition chitosan/citric/glycerol/magnesium oxide (1 wt%:1 wt%:75 vol%:10 wt%) has high mechanical properties than other films. The effects of different irradiation doses on the mechanical, thermal and antibacterial activity were investigated. The tensile strength enhanced by increasing irradiation dose up to 10 kGy and the elongation negligible changed as irradiation dose increased. The thermal stability slightly increased up to dose 2.5 kGy then decreased with dose increment. The antimicrobial activity film was studied against white mulberry-borne bacterial pathogens either Gram positive or Gram negative bacteria and has positive impact of gamma irradiation on the antimicrobial activity. The use of the selected chitosan nano-composite film which irradiated by dose of 2.5 kGy and has magnesium oxide of average particle size 54.3 nm as new packaging materials found to improve storage quality and shelf-life of mulberry fruit.     

Properties of Composite Panels Made from Tetra-Pak and Polyethylene Waste Material

The objective of this study was to evaluate some of the properties of experimental composite panels manufactured from waste packaging materials without using any additional binders. Particles from three types of materials, namely Tetra-Pak, food packaging films (FPEF) as recycled stretch wraps, and candy polyethylene wrappers (CPEW) were used at different ratios in the panels at a target density of 900 kg/m³. Modulus of rupture (MOR), screw holding strength and dimensional stability in the form of thickness swelling and water absorption of the panels were determined according to European (EN) standards. Based on the findings in this work it was determined that the ratio of different raw materials significantly influenced overall properties of the samples. The highest MOR value of 15.5 MPa was determined for the samples having 40 % Tetra-Pak and 60 % CPEW particles. Modulus of rupture values of the panels decreased with decreasing content of CPEW in the samples. The increased content of Tetra-Pak particles in the samples also resulted in reduction of their strength characteristics and dimensional stability. Properties of the samples considered in this work satisfied minimum requirements of typical particleboard stated in EN standards. It appears that such waste material would have potential to be used as raw material for value-added composite production using no adhesive in the panels and, therefore, such panels would possibly create significant ecological impact as green product.     

Radiation Crosslinking of Poly(Butylene Succinate) in the Presence of Inorganic Material and Its Biodegradability

Three kinds of poly(butylene succinate)s (PBS) with different molecular weight were irradiated with electron beams in the presence of inorganic material. Fourteen kinds of inorganic materials were used in this work. The presence of inorganic material inside cross-linked PBS samples enhances the yield of gel formation. The heat stabilities of PBS samples were checked; it was found that silicon dioxide and carbon black significantly improve these properties. Enzymatic and soil burial tests were performed; the presence of these inorganic materials in cross-linked PBS accelerates the rate of biodegradation.     

Exfoliation and Decoration of Graphene Sheets with Silver Nanoparticles and Their Antibacterial Properties

High quality graphene sheets (GRP) have been exfoliated using facile one pot method through direct ultrasonication of graphite in the presence of polyvinyl alcohol. The GRP were decorated with silver nanoparticles (AgNPs) producing graphene–silver nanoparticle composites. The effect of variation of graphite and silver salt mass ratios on the morphology and performance of produced composites was studied. The size of AgNPs decorated on GRP has been tuned with synthesis method optimization. The average size of AgNPs was found to be in the range of 8.6–15.6 nm. Cotton–polyester blend textile fabrics were treated with the new smart developed composite as antibacterial agent producing new composites. A significant inhibition of bacterial growth has been observed for graphene–silver nanoparticle composite and the antibacterial efficiency was optimized. The clear inhibition zone for textiles treated with new developed composite and AgNPs alone was recorded as 12 and 1.75 mm respectively, achieving more than six fold improvement.     

TG-DSC and FTIR study on pyrolysis of irradiation cross-linked polyethylene

Irradiation cross-linked polyethylene (PEX) and irradiation cross-linked polyethylene with carbon black filler (CB-PEX) are two types of scraps, generated in electric cable production. Their pyrolysis is studied in this work using instrumental TG\DSC\FTIR techniques and kinetic analysis. The experiments are performed at a constant heating rate of 10 °C/min in nitrogen flow at atmospheric pressure. It is found that the main pyrolysis stage is in the temperature range of 395–503 °C for PEX, and in range of 408–515 °C for CB-PEX. In the main pyrolysis stage, CB-PEX requires more external heat than PEX does. Olefins are the major products of pyrolysis for both materials, but they are quite different in their composition and molecular weight distribution. PEX can be converted almost quantitatively into volatile compounds. CB-PEX has a stronger coking tendency, as well as a larger residue composed of carbon black.     

Synthesis,Characterization and Environmental Applications of a New Bio-Composite Gelatin-Zr(IV) Phosphate

Gelatin-Zr(IV) phosphate composite (GT/ZPC) was synthesized by sol–gel method. Different techniques viz. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray powdered diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for the characterisation of GT/ZPC composite ion exchanger. The ion exchange capacity (IEC) of GT/ZPC was observed to be better (1.04 meq g^?1) than its inorganic counterpart (0.64 meq g^?1). The pH studies revealed the monofunctional nature of GT/ZPC with one inflection point. The distribution studies showed that the GT/ZPC was highly selective for Cd²⁺ as compare to other metal ions. The environmental applicability of ion exchanger has been analysed for binary separations of metal ions using column method. Cd²⁺ was effectively removed from synthetic mixture of metal ions (Zn²⁺, Pb²⁺, Ni²⁺, Co²⁺ and Cu²⁺).     

Mechanical Recycling of PLA Filled with a High Level of Cellulose Fibres

Composites consisting of 30 vol% PLA and 70 vol% cellulose fibres were prepared with compression moulding. In the first part of the study, the recyclability of this composite material was investigated by grinding the material and using the recyclate obtained as a filler for PLA. Thus, the recyclate was compounded with PLA in loadings ranging from 20 to 50 wt%. The composites obtained were characterised by tensile tests, Charpy impact tests, DMTA, and SEM. Tests showed that the recyclate had a relatively good reinforcing effect. Stress at break increased from about 50 to 77 MPa and the modulus increased from 3.6 to 8.5 GPa. In the second part of the study, the ability to mechanically recycle the composites obtained was evaluated by repeated processing. Composite with two loadings of the recyclate (20 wt% and 50 %) was injection moulded repeatedly, six times. Tests showed that the composite material with 20 wt% recyclate could withstand six cycles relatively well, while the composite with the higher load degraded much more quickly. For the composites with 50 wt% recyclate, signs of polymer degradation could be seen already after reprocessing the composite once.     

Effect of Nano-SiO<Subscript>2</Subscript> and Bark Flour Content on the Physical and Mechanical Properties of Wood–Plastic Composites

The aim of this study is to evaluate the impact of nano-SiO₂ and bark flour (BF) on the natural fiber–plastic composites engineering properties made from high density polyethylene (HDPE) and beech wood flour (WF). For this purpose, WF and BF in 60 mesh size and weight ratio of (50, 0 %), (30, 20 %), (10, 40 %) and (0, 50 %) respectively were mixed with HDPE. In order to increase the interfacial adhesion between the filler and the matrix, the maleic anhydride grafted polyethylene was constantly used at 3 wt% for all formulations as a coupling agent. The nano-SiO₂ particles with weight ratio of 0, 1, 2, and 4 % were also utilized to enhance the composites properties. The materials were mixed in an internal mixer (HAAKE) and then the bark and/or wood–plastic composite samples were made utilizing an injection molding machine. The physical tests including water absorption and thickness swelling, and mechanical tests including bending characteristics and un-notched impact strength were carried out on the samples based on ASTM standard. The results indicated that as the BF content increased in the composite, mechanical and physical properties were reduced, but the given properties were increased with the addition of nano-SiO₂. The addition of nano-SiO₂ had a negative impact on the physical properties, but when it was up to 2 %, it increased the impact strength.     

Some Investigations on the Nylon 6/Zn Composite Material Obtained by Simultaneous Anionic Polymerization-Molding Process

This study is concerned with the behavior of samples based on nylon 6/zinc (Ny6/Zn) composite material in high salinity water that contains NaCl (3.5 wt%) and in aqueous solution of HCl (0.5 N and 1 N). The samples were obtained from parts prepared by in situ anionic ring-opening polymerization of ?-caprolactam (CL) in the presence of zinc (Zn), as filler (15 wt%) using the rotational molding technique. This type of composite was evaluated by the testing of swelling degree, structural modifications, evolution of hydrogen and electrochemical behavior. The properties of Ny6/Zn composite material have ascertained through the combined use of more analysis methods: attenuated total reflectance Fourier transform infrared spectroscopy, wide-angle X-ray diffraction technique, scanning electron microscopy, swelling and electrochemical measurements. It was revealed that regarding swelling behavior the Ny6 matrix has an important role while Zn filler contributes especially to the (electro)chemical corrosion.     

Mechanical Properties of Layered Laminated Woven Bamboo <Emphasis Type="Italic">Gigantochloa Scortechinii</Emphasis>/Epoxy Composites

This study investigated the application of bamboo as a natural composite, in which its potential as a composite material had been examined for 2–6 layers. In precise, the woven bamboo (BW) formed the culm fiber composite with an average of 0.5 mm thickness and 5.0 mm width strip. In addition, this study looked into a specific type of bamboo species known as Gigantochloa Scortechinii (Buluh Semantan), which can be found in Malaysia. This laminated plain BW, which had been reinforced with epoxy (EP), was developed by applying the hand lay-up technique. After that, the specimens were characterized via mechanical analyses, for instance, tensile, flexural, hardness, and impact tests. As a result, the 2-layer BW had displayed rather excellent results chiefly due to the incorporation of epoxy composite, although this is exceptional hardness value.     

The Effects of Additives on the Biodegradation of Polycaprolactone Composites

Because environmental pollution caused by plastic waste is a major problem investigations concerning biodegradable packaging are important and required. In this study, the biodegradation of PCL composite films with organic (glycerol monooleate and oleic acid) and inorganic additives (organo nano clay) was investigated to understand which additive and the amount of additive was more effective for biodegradation. The relationship between the degree of crystallinity and the effect of additives on the biodegradability of polycaprolactone (PCL) was examined. PCL composite films were prepared using organo nano clay (0.1–0.4–1–3 wt%) and oleic acid (1–3–5 wt%) or GMO (1–3–5 wt%). The 35 films prepared with PCL (P), clay (C), oleic acid (O), or glycerol monooleate (G) are coded as P_C#wt%_O (or G)#wt%. The composite films, P_C0.4_O5 contains 0.4 wt% clay and 5 wt% oleic acid and the P_C3_G1 contains 3 wt% clay and 1 wt% glycerol monooleate. The biodegradation of PCL films in simulated soil was studied for 36 months. The films were periodically removed from the simulated soil and film thicknesses, weight losses, visual changes, crystal structures, and a functional group analyses were performed. PCL composite films are separated into three groups, depending on degradation time, (1) films that degraded before 8 months (fast degradation), (2) films that degraded around 24 months (similar to neat PCL), and (3) films that take longer to degrade (slow degradation). The films in the first group are PCL films with 1 and 3 wt% clay additive and they begin to biodegrade at the 5th month. However, a composite film of PCL with only 0.4 wt% clay and 5 wt% GMO addition has the shortest degradation time and degraded in 5 months. The films in the last group are; P_G3, P_G5, P_C0.1, P_C0.1_O1, and P_C0.1_O5 and they took around 30 months for biodegradation. It was observed that increasing the organo nanoclay additive increases the biodegradability by disrupting the crystal structure and causing a defective crystal formation. The addition of GMO with organo nano clay also accelerates biodegradation. The addition of organo nano clay in an amount as small as 0.1 wt% acts as the nucleating agent, increases the degree of crystallinity of the PCL composites, and slows the biodegradation period by increasing the time.     

Synthesis of CS/PVA Biodegradable Composite Nanofibers as a Microporous Material with Well Controllable Procedure Through Electrospinning

In this study, we have showed a facile route for fabrication of a novel microporous material based on chitosan (CS) and poly(vinyl alcohol) (PVA) biodegradable nanofibers that have high specific surface area, considerable porosity, and small diameter. Scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area analysis, and CHNS/O elemental analyser were applied to characterize the fabricated CS/PVA composite nanofibers. Moreover, the influences of spinning conditions including concentration, voltage, electrospinning distance, and flow rate, on size distribution and pore diameter of the final product were systematically studied using 2^k?1 factorial design experiments, and the response surface optimization was used for determining the best synthesis parameter. The results obtained from 2^K?1 factorial design experiments showed that electrospinning parameters influenced the size distribution and pore diameter of the CS/PVA microporous material. Based on the response surface methodology, the CS/PVA product could be obtained with a high microporous diameter of 1.8 nm and a small diameter distribution of 15.0 nm under optimized conditions. The obtained results showed that the fabricated samples could be utilized in different applications.     

Arsenic Removal from Dilute Solutions by High Surface Area Mesoporous Iron Oxyhydroxide

Mesostructured iron oxyhydroxide (FeO _x ) and iron oxyhydroxide–phosphate (FeO _x P) composites were organized using dodecylsulfate surfactant as a template. X-ray diffraction studies depicted a lamellar structure of the product. Ion exchange and solvent extraction methods were employed for the removal of the surfactant. Carboxylate ions exchanged lamellar type mesostructured material reorganized to a wormhole-like mesoporous material when heated under N₂ atmosphere. Surfactant was completely removed by carboxylate ions as observed by the Fourier transform infrared spectra. High surface area acetate-exchanged FeO _x (230 m² g^?1) was obtained after the surfactant removal from the composite (2.8 m² g^?1). Surface area of acetate-exchanged FeO _x P was the highest (240 m²g^?1) after the removal of the surfactant. Local structure of iron species of FeO _x was investigated by X-ray absorption fine structure spectroscopy. Further, Fe···Fe bond appeared at 3.21–3.25 Å with coordination number 2–3, showing a high degree of un-saturation of Fe···Fe bonds. As compared with bulk iron oxyhydroxide and iron-intercalated montmorillonite, the mesoporous iron materials were highly effective for arsenic removal from low concentrations of aqueous solutions. Furthermore, mesoporous iron materials were stable in aqueous phase.     

Production and Purification of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Degrading Enzyme from Streptomyces sp. AF-111

A poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) degrading bacterial strain designated as AF-111 was isolated from sewage sludge sample. The bacterium was identified by 16S rRNA gene sequencing. The results revealed that strain AF-111 showed 99 % similarity with Streptomyces althioticus strain NRRL B-3981 and designated as Streptomyces sp. strain AF-111. An extracellular PHBV depolymerase enzyme was produced under optimized conditions and purified through ammonium sulphate fractionation and column chromatography. The enzyme was purified to homogeneity, indicated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and molecular weight was found to be approximately 51 kDa. Effect of temperature, pH, metal ions and inhibitors on the PHBV depolymerase activity was determined. The enzyme was stable at wide range of temperature (35–55 °C) and pH (6–8). PHBV depolymerase was stable in the presence of different metal ions except iron and zinc which had inhibitory effect on depolymerase activity. Both ethylenediamine teteracetic acid and phenylmethyl sulphonyl fluoride strongly inhibited enzyme activity which indicates that this enzyme belongs to the serine hydrolase family like other polyhydroxyalkanoate depolymerases. The results show that a depolymerase from strain AF-111 can effectively degrade PHBV, therefore, it can be applied in the process of biochemical monomer recycling.     

Extracting humic acids from digested sludge by alkaline treatment and ultrafiltration

The concentration of hardly biodegradable humic substances in sludge would relatively increase after anaerobic digestion due to the degradation of other organic substances. Thus, extracting humic substances from digested sludge as a liquid organic fertilizer was tested using alkaline treatment and ultrafiltration, and the dewaterability of the residual sludge was also tested. The results showed that the contents of humic acids and fulvic acids in digested sludge were 16.4 mg/g total solids and 88.9 mg/g total solids, respectively, and most of the humic acids had a molecular weight higher than 50 kDa. Hence, the membrane with a molecular weight cut-off of 50 kDa was used for humic acids recovery from the centrifugation supernatant after alkaline sludge disintegration with an optimum NaOH dose of 0.1 mol/L. Under these conditions, the total concentration of humic acids and fulvic acids was 4239 mg/L in the retention solution, which can be further concentrated and processed for liquid fertilizer. The total recovery rate of sludge humic acids and fulvic acids was about 25 %. The dewatering performance of the residual sludge was better than that of the untreated sludge when the residual sludge was diluted to a water content of 95–98 % and then conditioned with polyacrylamide at a dose of 10–30 mg/L.     

Stiff Biodegradable Polylactide Composites with Ultrafine Cellulose Filler

Polylactide (PLA) composites with 10–30 wt% of commercial fine grain filler of native cellulose were prepared by melt-mixing, and examined. The composite films had esthetic appearance, glossy surface, creamy color and density close to that of neat PLA. Good dispersion of the filler in PLA matrix was achieved. The composites were stiffer than neat PLA; in the glassy region the storage modulus increased by approx. 30 %. The tensile strength of the composite materials in the temperature range from 25 to 45 °C was similar to that of neat PLA. No marked decrease in molar mass of PLA in the composites occurred during processing in comparison to neat PLA. Moreover, thermogravimetry experiments demonstrated good thermal stability of the composites; 5 % weight loss occurred well above 300 °C.     

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/Organomodified Montmorillonite Nanocomposites for Potential Food Packaging Applications

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) is a versatile, biobased and biodegradable copolymer from the family of polyhydroxyalkanoates. This study aims to further ameliorate its properties in order to enhance its applicability for food packaging purposes through preparation of organomodified montmorillonite clay (OMMT) nanocomposites. Nanocomposites based on pure PHBHHx as well as commercial PHBHHx granulate, after a previous dry-mixing with OMMT in concentrations of 1, 3, 5 and 10 wt%, were prepared using melt blending and compression molding. Investigation of the samples showed well dispersed nanofiller and highly intercalated nanocomposites, resulting in a continuous decrease in gas permeability, lowering O₂, CO₂ and water vapor permeability with about 5–7 % and approximately 40 % at OMMT concentration of 1 and 10 wt%, respectively. Besides gas permeability, other properties were affected as well. Thermal stability of the samples increased gradually up to 5 wt% nanofiller, but was reduced at 10 wt%. In order to investigate the effects of OMMT and molecular weights on PHBHHx crystallization, nanocomposites were also produced by solvent-casting and compared to those obtained by melt-blending. Crystallization was retarded, because of severe lowering of molecular weight due to processing-induced chain scission, catalyzed by OMMT moisture. However, this reduction was counteracted for a large part by using commercial PHBHHx granulate, which has shown better crystallization properties. The samples were rendered increasingly more brittle, displaying higher Young’s modulus and severely reduced elongation at break. From this study it appeared that, upon viewing all affected properties as a whole, the sample based on commercial PHBHHx and containing 3 wt% OMMT shows most promise for possible applications, however further research must be performed in order to exploit their fullest potential.     

Experimental Investigation of Cellulose/Silver Nanocomposites Using In Situ Generation Method

Cellulose gel films were prepared by regeneration process using pre-cooled aq.(8 wt% LiOH + 15 wt% urea) mixture as solvent and ethyl alcohol as non solvent. The Terminus cattapa leaf extract diffused wet cellulose films were then dipped in 1–5 mM aq.AgNO₃ solutions to allow in situ generation of silver nanoparticles (AgNPs). Besides the in situ generation, some AgNPs were also formed outside the wet films in the solution. The AgNPs formed outside the films were observed under transmission electron microscope and scanning electron microscope. The nanocomposite films were also characterized by Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis and tensile test. The thermal stability of the composite films was lower than that of the matrix up to a temperature of ~300 °C and afterwards showed a reverse trend. The tensile strength of the nanocomposite films was found to be higher than the matrix but decreased with increasing concentration of aq.AgNO₃. The cellulose/AgNPs composite films showed good antibacterial activity against E. coli (gram positive) and Bacillus sp. (gram negative). Based on the aforementioned properties, the cellulose/AgNPs composite films can be considered for antibacterial packaging and medical applications.     

Tar and soot generation behaviors from ABS,PC and PE pyrolysis

In this study we performed a non-isothermal thermogravimetric analysis on three thermoplastics—ABS, PC and PE. The Coats and Redfern method (Nature 201:68–69, 1964) was then used to approximate the kinetic parameters of each material. In addition, we performed a series of pyrolysis experiments in a batch reactor, for each plastic. The experiments were performed over the temperature range of 600–1000 °C at a constant residence time. The liquid and solid products of the pyrolysis, were collected, separated and weighted. Those products were categorized as soot, tar and char (PC only), and their relative weight to initial sample weight (DAF) was plotted against the temperature. The tar measured was exclusively medium to high molecular weight (>80 g/mol). Results revealed that relative tar and soot production, for all three materials, first increases and then decreases with temperature increase. The maximum achieved tar yields for ABS, PC and PE were at 700, 650 and 800 °C, respectively; and the maximum soot yields were at 1000, 1000, 950 °C, respectively.