Volume 11 Issue 2

A novel intermittent microwave-assisted carbonization method was developed to prepare bio-char (BWSC) from Durian wood sawdust (BWS). The BWS was further activated using a base-catalytic approach to produce a graphitic form of bio-carbon (BWSAC). A three factor, two-level central composite (CCD) experimental design was used to maximize Pb(II) ion removal from aqueous solution using BWSAC. Three independent variables (initial pH of solution (pH0) ranging from 2 to 8, initial metal ion concentration of Pb(II) cations (C0) ranging from 50 to 100 mg/L, and contact time (Ct) ranging from 10 to 300 min) were consecutively coded as x1, x2, and x3 at three levels (−1, 0 and 1) of the design matrix. The experimental conditions in terms of actual factors were determined to be x1 (pH0) = 5.86, x2 (C0) = 57.77 mg/L, and x3 (temperature) = 53.85 °C, and the resultant Pb(II) ion removal efficiency (y1) obtained was 92.73%, with a model desirability of 0.974. The change in physiochemical properties after carbonization as well as activation was observed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer, Emmett and Teller surface area analysis (BET), Thermogravimetric analysis (TGA), Ultimate analysis, and Fourier transform infrared spectroscopy (FTIR).

In the first stage of pulp bleaching, the quantity of added chemicals (ClO2 and/or Cl2) is commonly controlled by kappa factor, based on a kappa number online analyzer together with a compensated brightness control scheme as a feedback strategy. However, a kappa number analyzer is not always available, so the bleaching quality relies heavily on the chemical dosage set-point chosen by the operators. In this study, an improved model for the chlorination stage brightness optimization was proposed, based on brightness and residual chemicals before pulp enters the bleaching tower. Additionally, the experience of operators of (C95/D5) bleaching was employed in order to find an optimum chemical dosage set-point quickly. The golden section search algorithm (i.e., ‘0.618 method’) was used to find the optimum chemical dosage in this paper. After applying the proposed method in a pulp mill (C95/D5) bleaching stage, the chlorination stage brightness shifted from 62.9% ISO to the target value 60.7% ISO. Meanwhile, the standard deviation was reduced from 3.0 to 2.5.

Four fast-growing wood species were treated, including two hardwood species and two softwood species, with either furfurylation or acetylation for comparison and analysis. The properties of the resultant woods, including weight percent gain, bulking effect, leach rate, anti-swelling efficiency (ASE), and color changes, were compared comprehensively. The effects of wood species on modification efficiency were also evaluated by morphological analysis. The results indicated that the species of wood had little effect on successful acetylation, but that wood species with more open pits and loose and ordered structures were best suited for furfurylation. Both types of modification resulted in wood samples with more uniform colors than untreated samples. Furfurylation caused considerable color changes in all of the wood samples; acetylation resulted in wood samples slightly lighter in color (lower ΔE* values). The differences in ΔE* values among the four wood species were primarily due to the natural differences in the color of the woods.

To investigate the influence of pH on the size and distribution of silver nanoparticles (Ag-NPs) as well as the antibacterial activity and catalytic performance of rice straw/silver nanocomposites (RS/Ag-NCs), Ag-NPs were synthesized on the surface of rice straw (RS) with various percentages of Ag-NPs (1.0, 5.0, 10.0, and 20.0 wt.%) under different temperatures and diverse pH values. The ultraviolet-visible spectroscopy of synthesized RS/Ag-NCs became noticeable with increased pH, and the peaks were blue-shifted to lower wavelengths. X-ray powder diffraction (PXRD) demonstrated the presence of pure Ag-NPs. Transmission electron microscopy (TEM) showed that the diameters of Ag-NPs on RS were between 7.78 and 2.84 nm at pH values of 8 to 10. The antibacterial activity of various sizes of Ag-NPs on RS was examined using Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) based on the well diffusion technique. Higher antibacterial activity was detected as the loading percentage of RS/Ag-NCs increased and particle size decreased. The superior catalytic performance of 20.0 wt.% RS/Ag-NCs was considered in a test reaction in 4-nitrophenol (4-NP) reduction in the presence of sodium borohydride (NaBH4) in an eco-friendly solvent at ambient temperature. The results represented the high-performance catalytic activity of 20.0 wt.% RS/Ag-NCs.

Amphoteric polyacrylamide (AmPAM) is a linear water-soluble polymer that has been applied in papermaking as an agent for flocculation, retention, filtration, and dry-strength improvement. However, AmPAM with different ranges of molecular weight (MW) have different properties in these processes. In this study, a series of AmPAMs were constructed with an anionic monomer, itaconic acid (IA), a cationic monomer, methacryloxyethyl-trimethyl ammonium chloride (DMC), and a main backbone of acrylamide (AM). Four factors influencing free radical polymerization, i.e., reaction temperature, pH, initiator load, and the concentration of monomers, were systematically investigated via an orthogonal test to determine their effects on the MW of AmPAM. Spectroscopy and isoelectric point assays were used to characterize the structure of the produced AmPAM, and the MW was assessed by calculating the viscosity. The reaction temperature had the greatest influence on the MW of AmPAM, followed by the solution pH and the initiator load. To determine the dry strength of papersheets containing AmPAM, the breaking length of handsheets was assessed after adding 0.5% AmPAM (based on fiber) with different MWs. The maximum value, 4.05 km, was 15.0% higher than the control and was obtained using AmPAM with a MW of 330 kDa.

In outdoor applications, the mechanical performance of wood-plastic composites (WPCs) is affected by UV radiation, facilitating moisture intake and damaging the wood-polymer interfacial region. The purpose of this study was to evaluate the effect of moisture absorption-desorption cycles (MADCs), and the exposure to UV radiation on the interfacial shear strength (IFSS) of WPCs with 40% pinewood residue and 60% high-density polyethylene. One of the WPCs incorporated 5% coupling agent (CA) with respect to wood content. The IFSS was evaluated following the Iosipescu test method. The specimens were exposed to UV radiation using an accelerated weathering test device and subsequently subjected to four MADCs. Characterization was also performed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The absorption and desorption of moisture was slower in non-UV-irradiated WPCs, particularly in those with the CA. The UV radiation did not significantly contribute to the loss of the IFSS. Statistically, the CA had a favorable effect on the IFSS. Exposure of the samples to MADCs contributed to reduce the IFSS. The FTIR showed lignin degradation and the occurrence of hydrolysis reactions after exposure to MADCs. SEM confirmed that UV radiation did not significantly affect the IFSS.

The astronomical increase in global energy demand makes locating energy sources other than fossil fuels worthwhile. The use of tropical biomass wood waste as a renewable energy source was investigated in this study. The thermal conversion analysis of Albizia gummifera (ayinre) was carried out in a thermobalance reactor via steam gasification under varying temperature (700 to 1000 °C) and steam partial pressure (0.020 to 0.050 MPa). The experimental data was evaluated using three gas-solid reaction models. The modified volume reaction model (mVRM) gave the overall highest coefficient of determination (0.9993) and thereby the best conversion prediction. The observed char activation constant rates (from paired reaction conditions) indicated, on average, an increase in reactivity as the parameters increased. The results showed that the activation energy of the mVRM gave the lowest value (32.54 kJ/mol) compared with those of the shrinking core model (SCM) and the volume reaction model (VRM) (49.29 and 49.89 kJ/mol, respectively).

Tar and char can be regarded as unwanted byproducts during the gasification process. In this study, three types of catalyst, i.e., biomass char (bio-char), nickel supported on biomass (Ni+bio-char), and nickel supported on bio-char (bio-char+Ni), were studied to compare the catalytic effects of different preparation methods on tar model compound removal. The structural characteristics of the three catalysts were also investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) methods. The results revealed that Ni+bio-char catalyst showed much higher activity for the reformation of toluene (C7H8) as a tar model compound than the other two catalysts. Toluene could be completely converted to small gas molecules at a conversion rate of 99.92% at 800 °C, and the maximum yield of gas was 432 mL/(mL C7H8). In particular, the H2 and CH4 yields were 339 and 85 mL/(mL C7H8) at 850 °C, respectively. An N2 absorption-desorption experiment demonstrated that the specific surface area of Ni+bio-char was 32.87 times that of bio-char and 8.39 times that of bio-char+Ni. Moreover, metallic nickel (Ni0) particles could be generated in the carbon matrix of Ni+bio-char catalyst. SEM analysis confirmed that the Ni+bio-char catalyst had a more porous structure. Nickel supported on biomass might be a promising catalyst for tar reformation because of its excellent catalytic activities.

Three alkali swelling methods were used to treat two kinds of kraft pulp fibers. The morphological and chemical properties of the treated fibers were elucidated in terms of alkali concentration, with the aim of developing bulky paper and conserving wood resources. The effects of beating before and after alkali swelling were examined. The water retention value of fibers increased when higher concentrations of NaOH were used for swelling. Alkali swelling increased fiber width, while fiber length decreased. With increasing NaOH concentration, fibers became curled or kinked; the crystalline structure changed from cellulose I to cellulose II, and the crystalline index decreased. Beating before and after the alkali swelling affected the swelling behavior of kraft pulps, but there was no distinct influence on the crystalline structure. The beating treatment before alkali swelling improved the alkali swelling of fiber. However, beating after the alkali treatment diminished the alkali swelling effects. In addition, the beating after alkali swelling straightened the curled fibers.

As a by-product generated from the processing of corn, the production in China of corncob (CC) is abundant, with up to 3.87 million tons per year. The biomass gasification industries make use of the CC residue as feedstock, but large volumes of generated corncob ash (CCA) requires daily disposal. In this study, CCA was characterized by laser particle size analyzer (LPSA), X-ray fluorescence (XRF), X-ray diffraction (XRD), thermal gravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy, and energy dispersive X-ray (SEM-EDX). XRF results showed that the CCA was rich in K, Ca, and P, indicating its potential as a soil amendment. High content of SiO2 in CCA revealed its potential as a pozzolan in blended cement concrete. XRD showed the presence of crystal phases such as potassium carbonate, sylvite, arcanite, quartz, calcite, and nitrite. SEM images revealed the high agglomeration of CCA. EDX gave evidence of the external surface of agglomerated particles coated with KCl. TG-DTA analysis indicates that decomposition of CCA has stepwise mechanism. The CCA powders through a 0.154 mm sieve showed a high specific surface area of 162.32 m2/g, average pore size of 12.17 Å with pore volume of 0.116 cm3/g. The carbon residue separated from CCA has the potential to be used as activated carbon.