Synthesis of Poly(vinyl) alcohol-cellulose nanocrystal hybrid aerogel

In this paper, a series of polyvinyl alcohol (PVA) aerogels hybrid with cellulose nanocrystal (CNC) was successfully prepared using freeze-drying process. The influence of different fractions of CNC and crosslinking agent; glutaraldehyde (GA) on the mechanical of PVA/CNC hybrid aerogels property was evaluated by means of compressive strength. Results show that the strength of hybrid aerogels has been improved with the addition of CNC and GA. Variation in the CNC and GA content also led to differences in the porous structure characteristics. Nevertheless, higher content of GA caused adverse effect to the strength of hybrid aerogel which associated to the excessive crosslinking and smaller number of pores formation as evident from scanning electron microscopy (SEM) analysis

Characterization of poly(vinyl) alcohol based aerogel assisted by cellulose nanocrystal

A versatile and economic synthetic material is successfully prepared using a low-cost polyvinyl alcohol (PVA) and renewable cellulose nanocrystal (CNC) obtained from oil palm biomass through freeze-drying process. The PVA-based aerogels were incorporated with the CNC and glutaraldehyde (GA) which acted as nanofiller and crosslinker, respectively. The properties of fabricated hybrid aerogel samples were measured, and analyzed using compression testing, scanning electron microscope (SEM) and Barrett-Joyner-Halenda (BJH). The presence of CNC and GA crosslinkers have improved the compressive strength of PVA aerogel. The SEM analysis revealed that both materials affects the pore structures in term of its morphology, size and volume. The results of pore volume and volume is supported with the BJH results

Influence of iron (II) oxide nanoparticle on biohydrogen production in thermophilic mixed fermentation

The effect of initial pH, metal oxide and concentration of nanoparticles (NP) on hydrogen production were investigated in batch assays using glucose-fed anaerobic mixed bacteria in thermophilic condition of 60 �C. Two type of metal oxide nanoparticles, iron (II) oxide and nickel oxide, were tested and both metal capable of increasing the hydrogen yield about 34.38% and 5.47% higher than the control test. The experiments on the effect of initial pH were done without adding the nanoparticles to determine the optimum pH for maximum hydrogen production, in which at pH 5.5, the maximum hydrogen yield has reached about 1.78 mol H2/mol glucose. However, at pH 5.5 and the optimal iron (II) oxide concentration of 50 mg/L, the maximum hydrogen yield has reached to 1.92 mol H2/mol glucose, and the hydrogen content was 51%. Furthermore, the analysis of metabolites has indicated that the hydrogen production follows the acetic acid pathway. In all experiments with metal oxide nanoparticles, the metal NP was not consumed by the microbes, and the amount of it at the end of the fermentation was similar to the starting amount, which can be concluded that it was acting as an enhancer to the system to improve the hydrogen production. These results suggest that the addition of iron (II) oxide nanoparticles in the system is the vital factor to enhance the hydrogen production

Indoor air quality (IAQ) in a naval ship after refit program: a time variation analysis

Refurbishments of the ship's external and internal structures are the main scopes of a refit program. These activities may affect the indoor air quality (IAQ) inside ships and increase the indoor air pollutants (IAP) concentrations onboard. Therefore, continuous IAQ monitoring is needed to determine IAP exposure to the ship's crew. This study evaluates the changes in IAQ conditions inside a naval ship over a two-time interval to determine the effect of compliance with the recommended engineering control measures proposed in the first assessment. Following the standard of the Industry Code of Practice on Indoor Air Quality 2010 (ICOP on IAQ 2010), seven IAQ parameters (temperature, relative humidity (RH), carbon dioxide (CO2), respirable particulates/particulate matter (PM10), total volatile organic compounds (TVOC), bacterial count, and fungal count) were measured in two assessment phases. The first phase was conducted after the ship completed the refit program, and the second phase began three months later, following the execution of the recommended engineering control measures. According to the findings of this study, all IAQ parameters improved when compared to the first phase assessment. However, some of the readings were still non-compliance with the standards of ICOP on IAQ 2010. In conclusion, the ship's IAQ parameters were improved following the recommended engineering control measures, although more enhanced approaches were required to ensure all parameters complied with the ICOP on IAQ 2010

Thermophilic biohydrogen production from palm oil mill effluent: Effect of immobilized cells on granular activated carbon in fluidized bed reactor

In this study, the performance of immobilized cells on granular activated carbon (GAC) for thermophilic biohydrogen production is determined using POME as a fermentation substrate. The immobilized cells are formed at different pH medium using sugar composition characterized in the POME. The pH 6 revealed the optimum pH used for biofilm development with HPR of 2.8 mmol H2/L h. The effect of sugar utilization by the immobilized cells on GAC are determined at different sugar concentration using the Monod model prior validated the performance of the cells in the fluidized bed reactor (FBR). From the model, 0.316 ± 0.013 h−1 of maximum specific growth rate was obtained at 20 g/L sugar used and was keep increasing to the maximum of 30 g/L of sugar used with HPR 2.6–2.8 mmol H2/L h. Lastly, the POME-enriched nutrients are used as the carbon source in the fluidized bed reactor (FBR). The highest HPR obtained was at HRT 12 h, (5.2 mmol H2/L h) and HY of 1.24 mol H2/mol sugar. The screening of the microbial population by DGGE revealed that the Thermoanaerobacterium thermosaccharolyticum sp. was dominant for all the HRTs, thereby indicating that this bacterium is resilient towards environmental disturbances

Physical and mechanical evaluation of porous asphalt incorporated with untreated and treated waste cooking oil

The vast amount of waste cooking oil (WCO) has invited odds effects on the environment when disposed of improperly. Incorporating waste materials into asphalt mixture is common practice these days as it minimizes the amount of waste material as well as improves the performance of the mixture. WCO is known for its natural fluidity characteristics, wherein affecting good cracking performance at low temperature, yet indicate poor rutting resistance at high temperature. Plus, less strength in porous asphalt has worsened the rutting condition. Hence, pretreatment of WCO is suggested before the modification was done. In this study, WCO is being treated with chemical treatment of the transesterification process. Then, the modified binder of 5%, 10%, 15% and 20% untreated and treated WCO were tested with physical testing of penetration and softening point temperature. Later, a similar percentage of untreated and treated WCO were incorporated into porous asphalt mixture to analyze the mechanical performance of Marshall Stability, Flow and Stiffness. The result of porous asphalt mixture with 10% treated WCO showed an improvement in Marshall Stability, Flow and Stiffness. It can be concluded, samples with treated WCO indicated remarkable performance in terms of physical and mechanical evaluation, owing to similar polarity which enhances good interaction bonding that strengthens the asphalt mixture

Synergistic enhancement of biohydrogen production by supplementing with green synthesized magnetic iron nanoparticles using thermophilic mixed bacteria culture

The production of biohydrogen can be improved by focusing on the nutrients needed by fermentative bacteria like iron. Iron reacts with the [Fe-Fe]-hydrogenase enzyme within the mixed bacteria culture for optimum hydrogen release. Iron nanoparticles (NPs) are attractive due to its unique properties and high reactivity. It can be produced through green synthesis, a more eco-friendly and relatively lower cost process, by using iron salt as precursor and green coconut shell extracted by deep eutectic solvent (DES) as reducing agent. The coconut shell extract consists of phytochemicals that help in producing poly�disperse magnetic iron oxide nanoparticles at ~75 nm in size. The addition of optimum concentration of 200 mg Fe/L magnetic iron NPs resulted in the maximum cumulative hydrogen production, glucose utilization and hydrogen yield of 101.33 mL, 9.12 g/L and 0.79 mol H2/mol glucose respectively. Furthermore, the kinetic analysis on Gompertz model using the optimum magnetic iron NPs concentration showed that the hydrogen production potential (P) and hydrogen production rate (Rm) increased to 50.69 mL and 3.30 mL/h respectively and the lag phase time reduced about 7.12 h as compared with the control experiment (0 mg Fe/L). These results indicated the positive effects of magnetic iron NPs supplementation on fermentative biohydrogen production of mixed bacteria culture and proved the feasibility of adding the magnetic iron NPs as the micronutrient for enhancement of such hydrogen production system

Isolation and characterization of biohydrogen-producing bacteria for biohydrogen fermentation using oil palm biomass-based carbon source

The effectiveness of biohydrogen conversion from biomass sources is governed by the selection of ideal biohydrogen-producing bacteria to achieve high and consistent production performance. The aim of this research was to isolate and identify a biohydrogen producer in local soil samples, as well as to evaluate its fermentability in biohydrogen production from oil palm empty fruit bunches (OPEFB). To this end, preliminary identification was performed using morphological, phenotype, biological, and 16s rRNA analyses. The fermentability of the isolate was further evaluated in a serum bottle and then in a 1.5 L anaerobic column bioreactor (ACBR) to investigate the potential for biohydrogen production using two OPEFB-based carbon sources: hydrolysate of ammonia fiber expansion (AFEX)-pretreated OPEFB and molasses from dilute acetic acid (DAA)-pretreated OPEFB. The isolated strain, Enterobacter sp. KBH 6958, was found to be capable of producing biohydrogen from various carbon sources via the pyruvate:ferredoxin oxidoreductase (PFOR) pathway. The cumulative conversion of AFEX OPEFB hydrolysate was 45% higher than that observed in DAA OPEFB molasses fermentation in the production of biohydrogen. The biohydrogen yield after fermenting AFEX OPEFB hydrolysate with Enterobacter sp. KBH 6958 was 1.55 mol H2/mol sugar, with a maximum productivity of 98.1 mL H2/h (4.01 mmol H2/L/h), whereas butyrate (10.6 mM), acetate (11.8 mM), and ethanol (4.56 mM) were found to be the major soluble metabolites. This study successfully demonstrated the biotechnological conversion of OPEFB into biohydrogen using a locally isolated strain, which not only solves environmental issues associated with the industry but may also offer a solution to the world’s energy insecurity

Fabrication of Poly(Vinyl) Alcohol-Cellulose Nanocrystal hybrid aerogel

In this paper, a series of polyvinyl alcohol (PVA) aerogels hybrid with cellulose nanocrystal (CNC) was successfully prepared using freeze-drying process. The influence of different fractions of CNC and crosslinking agent; glutaraldehyde (GA) on the mechanical of PVA/CNC hybrid aerogels property was evaluated by means of compressive strength. Results show that the mechanical property of hybrid aerogels has been improved with the addition of CNC and GA. Variation in the CNC and GA content also led to differences in the porous structure morphologies. Nevertheless, higher content of GA caused adverse effect to the strength of hybrid aerogel which associated to the excessive crosslinking and smaller number of pores formation as evident from scanning electron microscopy (SEM) analysis

Screening of factors that influence the coagulation flocculation process of myco-coagulant produced in solid-state fermentation

The present study aims to determine the effects of the parameters that influence the coagulation/flocculation process as well as determine the optimal levels to be used in the optimization process using a myco-coagulant produced in solid-state fermentation for water treatment. Mixing speed, mixing time, the dose of myco-coagulant, initial turbidity, and time of settlement were examined through the one factor at a time (OFAT) approach. The factors were required to be tested further to choose the three levels required for the optimization process. The result obtained from the OFAT study indicated that the highest turbidity removal was observed at 10 ml/L of myco-coagulant dose, the optimal flocculating activity rate (%) is respectively rapid mixing at 200 rpm for 1 minute and slow mixing at 90 rpm for 22 minutes. On the other hand, the myco-coagulant showed good performance with increasing turbidity up to 800 NTU (92.22 %). The flocculating activity rate increased as settling time increased and stayed stable after one hour. The most influential parameters selected from OFAT will be subjected to the optimization process in order to achieve high flocculating activity. Based on OFAT experiments, FCCCD will be employed to determine the optimal conditions of the significant factors