Production of Poly(l-Lactide)-Degrading Enzyme by Amycolatopsis orientalis ssp. orientalis and Its Catalytic Ability in Biological Recycling of Poly(l-Lactide)

The fermentation conditions for poly(l-lactide) (PLA)-degrading enzyme production by Amycolatopsis orientalis ssp. orientalis were statistically optimized by response surface methodology. The optimal value of the most important factors was 0.39 % PLA and 0.34 % gelatin for 2.81 days of cultivation. Under these conditions, the model predicted a PLA-degrading activity of 155.30 U/l. The verification showed the production amount of 154.2 U/l. The crude enzyme from A. orientalis ssp. orientalis showed potent PLA-degrading ability, which is efficient for the biological recycling of PLA. Up to 4,000 mg/l of PLA granule was completely degraded within 5 days at 45 °C by the crude enzyme. l-lactic acid (600 mg/l) was obtained as a degradation product of PLA after only 2 h of incubation. The results indicated that the crude PLA-degrading enzyme from A. orientalis ssp. orientalis has the potential to degrade PLA to lactic acid for the recycling of PLA industry and waste disposal.     

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.     

Polymerization of l-lactide with SnCl2: A Low Toxic and Eco-friendly Catalyst

Polymerizations of l-lactide catalyzed either by neat SnCl₂ or by SnCl₂?+?difunctional cocatalysts were conducted in bulk at 180, 160 and 140 °C with variation of the Lac/Cat ratio and time. With neat SnCl₂ poly(L-lactide) having weight average molecular weights (uncorrected M_w’s) up to 190 000 g mol^?1 were obtained mainly consisting of linear chains. Addition of salicylic acid or 1,1-bisphenol yielded a higher fraction of cyclic polylactides but lower molecular weights. Furthermore, SnCl₂ was compared with Bu₂SnCl₂ and various other metal chlorides and the best results were obtained with SnCl₂. With ethyl L-lactate as initiator SnCl₂-catalyzed ROPs were performed at 120 °C and the lac/initiator ratio was varied. All these experiments were conducted under conditions allowing for comparison with ROPs catalyzed with neat Sn(II)-2-ethyhexanoate. Such a comparison was also performed with ε-caprolactone as monomer.

     

Pyrolysis of jute dust: effect of reaction parameters and analysis of products

Biowastes are becoming potential feedstocks for direct utilization or conversion to solid, liquid and gaseous fuels via various thermochemical routes. In this regard, jute dust which is a major agro-industrial waste in jute mills was pyrolysed in a fixed-bed reactor with an aim to study the product distribution and their characterization and to identify the optimum condition for bio-oil yield. The investigated process variables were temperature (400–700 °C), heating rate (10 and 40 °C/min) and nitrogen gas flow rate (50–250 ml/min). The yield of bio-oil is found to be maximum at 500 °C with a heating rate of 40 °C/min. However, further increase in temperature leads to decrease in bio-oil yield. Chemical compositions of the bio-oils were investigated using chromatographic and spectroscopic techniques such as ¹H NMR, FTIR and GC–MS. The heating value of the bio-oil is 26.71 MJ/kg. The study shows that jute dust have potential for conversion to bio-oil through the process of pyrolysis to supplement the petro-derived liquid fuel for heating and transportation applications after upgrading. The biochar produced as a co-product of jute dust pyrolysis can be a potential soil amendment with multiple benefits including increased soil fertility and C-sequestration.     

Recovery of glass fibers from glass fiber reinforced plastics by pyrolysis

Fiber-reinforced plastic sheets containing unsaturated polyester cross-linked with styrene, CaCO₃ and glass fibers as fillers were pyrolyzed in a helium and steam atmosphere in order to recover glass fibers and valuable organic pyrolysis products. Glass fibers were separated from CaCO₃ and CaO by dissolving calcium salts in hydrochloric acid. Residual organic material was burnt afterwards. Best results were obtained at a pyrolysis temperature of 600 and 700 °C, resulting in a large liquid fraction high in styrene, leaving little residual organic material on the surface of the glass fibers. At a pyrolysis temperature of 500 °C, the degradation of the polymer matrix was incomplete, and at 900 °C, glass fibers were destroyed in the presence of CaO, leaving CaSiO₃ as a product.     

The effect of clay catalyst on the chemical composition of bio-oil obtained by co-pyrolysis of cellulose and polyethylene

Cellulose/polyethylene (CPE) mixture 3:1, w/w with and without three clay catalysts (K10 – montmorillonite K10, KSF – montmorillonite KSF, B – Bentonite) addition were subjected to pyrolysis at temperatures 400, 450 and 500 °C with heating rate of 100 °C/s to produce bio-oil with high yield. The pyrolytic oil yield was in the range of 41.3–79.5 wt% depending on the temperature, the type and the amount of catalyst. The non-catalytic fast pyrolysis at 500 °C gives the highest yield of bio-oil (79.5 wt%). The higher temperature of catalytic pyrolysis of cellulose/polyethylene mixture the higher yield of bio-oil is. Contrarily, increasing amount of montmorillonite results in significant, almost linear decrease in bio-oil yield followed by a significant increase of gas yield. The addition of clay catalysts to CPE mixture has a various influence on the distribution of bio-oil components. The addition of montmorillonite K10 to cellulose/polyethylene mixture promotes the deepest conversion of polyethylene and cellulose. Additionally, more saturated than unsaturated hydrocarbons are present in resultant bio-oils. The proportion of liquid hydrocarbons is the highest when a montmorillonite K10 is acting as a catalyst.     

Aging of Toughened Polylactic Acid Nanocomposites: Water Absorption,Hygrothermal Degradation and Soil Burial Analysis

The environmental aging behaviour of montmorillonite (MMT) filled polylactic acid (PLA) nanocomposites (PLA/MMT) and linear low density polyethylene (LLDPE)-toughened PLA (PLA/LLDPE ratio = 90/10) nanocomposites (PLA/LLDPE/MMT) were investigated in this study. The nanocomposites were subjected to water absorption, hygrothermal degradation and soil burial analysis. Both PLA/MMT and PLA/LLDPE/MMT nanocomposites were immersed in distilled water at three different temperatures (room temperature, 60, and 90 °C) and the weight difference before and after immersion was calculated. The kinetics of water absorption for both nanocomposites followed the Fick’s second law of diffusion, where a linear relationship exists between the initial moisture absorption at any time t and t ^1/2 (the square root of time), followed by a horizontal plateau (saturation). The equilibrium moisture content (M _m ) and diffusion coefficient (D) of PLA nanocomposites increased with the addition of MMT (2 phr) and LLDPE. However, the D values of both nanocomposites decreased by increasing MMT (4 phr). The M _m for PLA/MMT and PLA/LLDPE/MMT nanocomposites increased by increasing immersion temperature (60 °C) and prolonged immersion resulted in hygrothermal degradation of both nanocomposites. The hygrothermal degradation studies showed that PLA degrades much faster at 90 °C as compared to 60 °C in both the nanocomposites. The addition of MMT and LLDPE improved the hygrothermal stability of PLA in both nanocomposites. Soil burial test revealed deterioration of impact strength in all samples while the rate of biodegradation was retarded in the presence of MMT and LLDPE.     

Chemical Recycling of Polyamide Waste at Various Temperatures and Pressures Using High Pressure Autoclave Technique

Chemical recycling of polyamide waste in water was studied using 0.5 L high pressure autoclave at temperatures of 150, 200, 210, 220,230 and 240 °C and at various pressures of 100, 200, 300, 400, 500, 600 and 700 psi (pound per square inch). Viscosity average molecular weight of the polyamide waste sample was determined by Ostwald method and recorded as 1.928 × 10³. The reaction was found to be first order with velocity constant in order of 10⁻² min⁻¹. The velocity constant and percent conversion of depolymerization reaction at 240 °C and 700 psi pressure were recorded as 2.936 × 10⁻² min⁻¹ and 99.99% respectively. The velocity constant was obtained on the basis of measurement of amine value. Kinetic and thermodynamic parameters such as energy of activation, frequency factor, enthalpy of activation were found to be 10.6 kJ mole⁻¹, 0.3719 min⁻¹ and 6.3 kJ mole⁻¹ respectively, at the optimum conditions for maximum depolymerization of polyamide waste.     

Recovery of materials from waste printed circuit boards by vacuum pyrolysis and vacuum centrifugal separation

In this research, a two-step process consisting of vacuum pyrolysis and vacuum centrifugal separation was employed to treat waste printed circuit boards (WPCBs). Firstly, WPCBs were pyrolysed under vacuum condition at 600 °C for 30 min in a lab-scale reactor. Then, the obtained pyrolysis residue was heated under vacuum until the solder was melted, and then the molten solder was separated from the pyrolysis residue by the centrifugal force. The results of vacuum pyrolysis showed that the type-A of WPCBs (the base plates of which was made from cellulose paper reinforced phenolic resin) pyrolysed to form an average of 67.97 wt.% residue, 27.73 wt.% oil, and 4.30 wt.% gas; and pyrolysis of the type-B of WPCBs (the base plates of which was made from glass fiber reinforced epoxy resin) led to an average mass balance of 72.20 wt.% residue, 21.45 wt.% oil, and 6.35 wt.% gas. The results of vacuum centrifugal separation showed that the separation of solder was complete when the pyrolysis residue was heated at 400 °C, and the rotating drum was rotated at 1200 rpm for 10 min. The pyrolysis oil and gas can be used as fuel or chemical feedstock after treatment. The pyrolysis residue after solder separation contained various metals, glass fibers and other inorganic materials, which could be recycled for further processing. The recovered solder can be reused directly and it can also be a good resource of lead and tin for refining.     

Thermal processing of paper sludge and characterisation of its pyrolysis products

Paper sludge is a waste product from the paper and pulp manufacturing industry that is generally disposed of in landfills. Pyrolysis of paper sludge can potentially provide an option for managing this waste by thermal conversion to higher calorific value fuels, bio-gas, bio-oils and charcoal. This work investigates the properties of paper sludge during pyrolysis and energy required to perform thermal conversion. The products of paper sludge pyrolysis were also investigated to determine their properties and potential energy value. The dominant volatile species of paper sludge pyrolysis at 10 °C/min were found to be CO and CO₂, contributing to almost 25% of the paper sludge dry weight loss at 500 °C. The hydrocarbons (CH₄, C₂H₄, C₂H₆) and hydrogen contributed to only 1% of the total weight loss. The bio-oils collected at 500 °C were primarily comprised of organic acids with the major contribution being linoleic acid, 2,4-decadienal acid and oleic acid. The high acidic content indicates that in order to convert the paper sludge bio-oil to bio-diesel or petrochemicals, further upgrading would be necessary. The charcoal produced at 500 °C had a calorific value of 13.3 MJ/kg.     

Characterization of products obtained from pyrolysis and steam gasification of wood waste,RDF, and RPF

Pyrolysis and steam gasification of woody biomass chip (WBC) obtained from construction and demolition wastes, refuse-derived fuel (RDF), and refuse paper and plastic fuel (RPF) were performed at various temperatures using a lab-scale instrument. The gas, liquid, and solid products were examined to determine their generation amounts, properties, and the carbon balance between raw material and products.The amount of product gas and its hydrogen concentration showed a considerable difference depending on pyrolysis and steam gasification at higher temperature. The reaction of steam and solid product, char, contributed to an increase in gas amount and hydrogen concentration. The amount of liquid products generated greatly depended on temperature rather than pyrolysis or steam gasification. The compositions of liquid product varied relying on raw materials used at 500 °C but the polycyclic aromatic hydrocarbons became the major compounds at 900 °C irrespective of the raw materials used. Almost fixed carbon (FC) of raw materials remained as solid products under pyrolysis condition whereas FC started to decompose at 700 °C under steam gasification condition.For WBC, both char utilization by pyrolysis at low temperature (500 °C) and syngas recovery by steam gasification at higher temperature (900 °C) might be practical options. From the results of carbon balance of RDF and RPF, it was confirmed that the carbon conversion to liquid products conspicuously increased as the amount of plastic increased in the raw material. To recover feedstock from RPF, pyrolysis for oil recovery at low temperature (500 °C) might be one of viable options. Steam gasification at 900 °C could be an option but the method of tar reforming (e.g. catalyst utilization) should be considered.     

Physicochemical and nutritional features of Gleditsia japonica shell biochar under different pyrolysis conditions

Journal of Material Cycles and Waste Management - This study aimed to investigate the effects of pyrolysis temperature (200–700 °C) and duration (2 h, 4 h) on...     

Pyrolysis characteristics of bean dregs and in situ visualization of pyrolysis transformation

Biomass is an important renewable and sustainable source of energy. Waste products from biomass are considered as attractive feedstocks for the production of fuel. This work deals with the pyrolysis of bean dregs, a biomass waste from soybean processing industry. A technique has been developed to study bean dregs pyrolysis by in situ visualization of bean dregs transformation in a quartz capillary under a microscope using a charge-coupled device (CCD) camera monitoring system. The technique enables us to observe directly the processes and temperatures of bean dregs transformation during pyrolysis. In situ visualization of reaction revealed that how oily liquids are generated and expulsed concurrently from bean dregs during pyrolysis. Pyrolysis characteristics were investigated under a highly purified N₂ atmosphere using a thermogravimetric analyzer from room temperature to 800 °C at different heating rates of 10, 30 and 50 °C/min. The results showed that three stages appeared in this thermal degradation process. The initial decomposition temperature and the peak shifted towards higher temperature with an increase in heating rate. Kinetic parameters in terms of apparent activation energy and pre-exponential factor were determined.     

Characteristic of heavy metals in biochar derived from sewage sludge

This study investigates the characteristic of heavy metals (Pb, Zn, Cu, Cd, Cr, Ni and As) in biochar derived from sewage sludge at different pyrolysis temperatures (300, 400, 500, 600 and 700 °C). The heavy metal concentrations, chemical speciation distribution, leaching toxicity, and bio-available contents were investigated using ICP-OES after microwave digestion, a sequential extraction procedure recommended by the Community Bureau of Reference (BCR), an improved nitric acid–sulphuric acid method, and diethylenetriamine pentaacetic acid (DTPA) extraction method, respectively. The results showed that a great percentage of the heavy metals remained in biochar, the concentrations of heavy metals in biochar (except Cd in B7) were higher than that in sludge, and the enrichment of the heavy metals in biochar enhanced with the pyrolysis temperature. Although the effect of pyrolysis temperature on the chemical speciation distribution, the leaching toxicity and the bio-available contents of heavy metals in biochar was inconsistent, the potential risk of biochar on soil and groundwater contamination was lower than sewage sludge.     

Pore structure and adsorption properties of carbonized material prepared from waste paper

We have already reported the adsorptivity and pore structure of activated carbon made from waste newspaper in order to use the waste paper for purposes other than paper-making stock. However, manufacturing the activated carbon may not necessarily be an advantageous method based on environmental concerns and the effective use of the resource because the reaction during the activating process is endothermic and the amount of carbon consumed is significant. Here, we examine the pore structure and adsorption properties of waste newspaper used as an adsorbent in the form of a carbonized material. Waste newspaper was carbonized for 2 h in the temperature range 400°–1000°C. The specific surface area of the carbonized material obtained, 418 m²/g, was highest for the sample carbonized at 800°C, which was equal to or greater than that of commercially available charcoal. Moreover, the iodine adsorption number of 581 mg/g was the highest and the rate of adsorption was the fastest for the sample carbonized at 800°C. However, the humidity control capability was highest for the material carbonized at 600°–700°C. It has been determined that it is advantageous to carbonize waste paper at 800°C in order to use the carbonized material as an adsorbent, while carbonization at 600°–700°C is more advantageous for use as a humidity control material. Received: June 23, 2000 / Accepted: January 17, 2001     

Analysis of the combustion and pyrolysis of dried sewage sludge by TGA and MS

In this study, the combustion and pyrolysis processes of three sewage sludge were investigated. The sewage sludge came from three wastewater treatment plants.Proximate and ultimate analyses were performed. The thermal behaviour of studied sewage sludge was investigated by thermogravimetric analysis with mass spectrometry (TGA-MS). The samples were heated from ambient temperature to 800 °C at a constant rate 10 °C/min in air (combustion process) and argon flows (pyrolysis process). The thermal profiles presented in form of TG/DTG curves were comparable for studied sludges. All TG/DTG curves were divided into three stages. The main decomposition of sewage sludge during the combustion process took place in the range 180–580 °C with c.a. 70% mass loss. The pyrolysis process occurred in lower temperature but with less mass loss. The evolved gaseous products (H₂, CH₄, CO₂, H₂O) from the decomposition of sewage sludge were identified on-line.     

Temperature-dependent pyrolytic product evolution profile for low-density polyethylene from gas chromatographic study

In this work, a product distribution study from thermal degradation of low-density polyethylene (LDPE) is presented. Thermal degradation of the polymer was investigated under dynamic condition in an inert environment using a thermo-gravimetric analyzer (TGA) coupled with evolved products’ analysis using a gas chromatograph (GC). Fractions evolved at nine different temperatures from 200 to 600 °C were injected into GC for a detailed product analysis. The main objective of the present investigation is to highlight the species-specific evolution profiles of LDPE pyrolyzates (C5–C44) at different stages of its degradation under an inert environment. Pyrograms have been analyzed in terms of amount of different products evolved at various pyrolysis temperatures. Volatile pyrolyzates essentially remain low at low decomposition temperature (200–300 °C) of the polymer, which gradually increase to attain a maximum at maximum decomposition temperature (470 °C) and finally level off at 600 °C. In the mechanistic approach adopted to understand the decomposition mechanism of LDPE, the following reaction types were considered: (a) main chain cleavage to form chain-terminus radicals; (b) intramolecular hydrogen transfer to generate internal radicals; (c) intermolecular hydrogen transfer to form both volatile products and radicals; and (d) β-scission to form both volatiles and terminally unsaturated polymer.     

Enhanced styrene recovery from waste polystyrene pyrolysis using response surface methodology coupled with Box–Behnken design

A work applied response surface methodology coupled with Box–Behnken design (RSM-BBD) has been developed to enhance styrene recovery from waste polystyrene (WPS) through pyrolysis. The relationship between styrene yield and three selected operating parameters (i.e., temperature, heating rate, and carrier gas flow rate) was investigated. A second order polynomial equation was successfully built to describe the process and predict styrene yield under the study conditions. The factors identified as statistically significant to styrene production were: temperature, with a quadratic effect; heating rate, with a linear effect; carrier gas flow rate, with a quadratic effect; interaction between temperature and carrier gas flow rate; and interaction between heating rate and carrier gas flow rate. The optimum conditions for the current system were determined to be at a temperature range of 470–505 °C, a heating rate of 40 °C/min, and a carrier gas flow rate range of 115–140 mL/min. Under such conditions, 64.52% WPS was recovered as styrene, which was 12% more than the highest reported yield for reactors of similar size. It is concluded that RSM-BBD is an effective approach for yield optimization of styrene recovery from WPS pyrolysis.     

Influence of Hygrothermal Ageing on the Physico-Mechanical Properties of Alkali Treated Industrial Hemp Fibre Reinforced Polylactic Acid Composites

30 wt% aligned untreated long hemp fibre/polylactic acid (AUL) and aligned alkali treated long hemp fibre/polylactic acid (AAL) composites were produced by film stacking and subjected to hygrothermal ageing environment along with neat polylactic acid (PLA). Hygrothermal ageing was carried out by immersing samples in distilled water at 25 and 50 °C over a period of 3 months. It was found that both neat PLA and composites followed Fickian diffusion. Higher temperature generally increased the Diffusion coefficient, D of neat PLA and composites, as well as shortening the saturation time. Neat PLA had the lowest D value followed by AAL composites and then AUL composites. After hygrothermal ageing, tensile and flexural strength, Young’s and flexural modulus and K _Ic were found to decrease and impact strength was found to increase for both AUL and AAL composites. AUL composites had greater overall reduction in mechanical properties than that for AAL composites after hygrothermal ageing. Crystallinity contents of the hygrothermal aged composites support the results of the deterioration of mechanical properties upon exposure to hygrothermal ageing environment.     

Optimization of Poly(<Emphasis Type="SmallCaps">dl</Emphasis>-Lactic Acid) Degradation and Evaluation of Biological Re-polymerization

Poly(dl-lactic acid) or PLA is a biodegradable polymer. It has received much attention since it plays an important role in resolving the global warming problem. The protease produced by Actinomadura keratinilytica strain T16-1 was previously reported as having PLA depolymerase potential and being applicable to PLA biodegradation, which was used in this work. Therefore, this research demonstrates the important basic knowledge on the biological degradation process by the crude PLA-degrading enzyme from strain T16-1. Its re-polymerization was evaluated. The optimization of PLA degradation by statistical methods based on central composite design was determined. Approximately 6700 mg/l PLA powder was degraded by the crude enzyme under optimized conditions: an initial enzyme activity of 200 U/ml, incubated at 60 °C for 24 h released 6843 mg/l lactic acid with 82% conversion, which was similar to the commercial enzyme proteinase K (81%). The degradable products were re-polymerized repeatedly by using commercial lipase as a catalyst under a nitrogen atmosphere for 6 h. A PLA oligomer was achieved with a molecular weight of 378 Da (n = 5). This is the first report to demonstrate the high efficiency of the enzyme to degrade 100% of PLA powder and to show the biological recycling process of PLA, which is promising for the treatment and utilization of biodegradable plastic wastes in the future.