A compact ultrawideband (UWB) antenna based on a hexagonal split-ring resonator (HSRR) is presented in this paper for sensing the pH factor. The modified HSRR is a new concept regarding the conventional square split-ring resonator (SSRR). Two HSRRs are interconnected with a strip line and a split in one HSRR is introduced to increase the electrical length and coupling effect. The presented UWB antenna consists of three unit cells on top of the radiating patch element. This combination of UWB antenna and HSRR gives double-negative characteristics which increase the sensitivity of the UWB antenna for the pH sensor. The proposed ultrawideband antenna metamaterial sensor was designed and fabricated on FR-4 substrate. The electrical length of the proposed metamaterial antenna sensor is 0.238 × 0.194 × 0.016 λ, where λ is the lowest frequency of 3 GHz. The fractional bandwidth and bandwidth dimension ratio were achieved with the metamaterial-inspired antenna as 146.91% and 3183.05, respectively. The operating frequency of this antenna sensor covers the bandwidth of 17 GHz, starting from 3 to 20 GHz with a realized gain of 3.88 dB. The proposed HSRR-based ultrawideband antenna sensor is found to reach high gain and bandwidth while maintaining the smallest electrical size, a highly desired property for pH-sensing applications.
In this study, porous silicon (PSi) was prepared and tested as an extended gate field-effect transistor (EGFET) for pH sensing. The prepared PSi has pore sizes in the range of 500 to 750 nm with a depth of approximately 42 µm. The results of testing PSi for hydrogen ion sensing in different pH buffer solutions reveal that the PSi has a sensitivity value of 66 mV/pH that is considered a super Nernstian value. The sensor considers stability to be in the pH range of 2 to 12. The hysteresis values of the prepared PSi sensor were approximately 8.2 and 10.5 mV in the low and high pH loop, respectively. The result of this study reveals a promising application of PSi in the field for detecting hydrogen ions in different solutions.
The objective of this study was to determine the effect chewing of two differently sized commercially available meswak might have on flow rate and pH of whole saliva. Twenty subjects participated in this study. They were distributed into two groups (A and B). Subjects in both groups A and B were asked to first chew on either a sized #1 or #2 cotton roll followed by the chewing of an equivalent sized piece of meswak (approximately 5 mm. and 10 mm. diameter) respectively. For subjects in group A, no differences in mean flow rate was seen after both the chewing regimes. In group B however, the increase in mean flow rate after the chewing of meswak compared to cotton roll was statistically significant at p < 0.05. Statistically significant lower values for pH were registered after the chewing of meswak compared to cotton roll in both groups A and B at p
The performance of advance photocatalytic degradation of 4-chlorophenoxyacetic acid (4-CPA) strongly depends on photocatalyst dosage, initial concentration and initial pH. In the present study, a simple response surface methodology (RSM) was applied to investigate the interaction between these three independent factors. Thus, the photocatalytic degradation of 4-CPA in aqueous medium assisted by ultraviolet-active ZnO photocatalyst was systematically investigated. This study aims to determine the optimum processing parameters to maximize 4-CPA degradation. Based on the results obtained, it was found that a maximum of 91% of 4-CPA was successfully degraded under optimal conditions (0.02 g ZnO dosage, 20.00 mg/L of 4-CPA and pH 7.71). All the experimental data showed good agreement with the predicted results obtained from statistical analysis.
Response surface methodology-Box–Behnken design (RSM-BBD) was employed to optimize the methyl orange (MO) dye removal efficiency from aqueous solution by cross-linked chitosan-tripolyphosphate/nano-titania compsite (Chi-TPP/NTC). The influence of pertinent parameters, i.e. A: TiO2 loading (0- 50 %), B: dose (0.04-0.14 g), C: pH (4-10), and D: temperature (30-50 oC) on the MO removal efficiency were tested and optimized using RSM-BBD. The F-values of BBD model for MO removal efficiency was 93.4 (corresponding p-value < 0.0001). The results illustrated that the highest MO removal efficiency (87.27 %) was observed at the following conditions: TiO2 loading (50% TiO2), dose (0.09 g), pH = 4.0, and temperature of 40 oC.
Lead contamination present in wastewater is one of the major problems due to its toxicity and persistence. This issue increased dramatically and led to the environmental and health concerns worldwide. Therefore, this study aims to remove lead from synthetic wastewater effluent by adsorption process. In this study, nanomaterial called graphene oxide (GO) is used as an adsorbent due to its mechanical strength and high surface area. The parameters were optimized using Fractional factorial design under response surface method. GO demonstrates high adsorption capacity, qmax = 500 mg/g at 100 mg/L of initial lead concentration and at optimum pH 9. Adsorption isotherm of lead was also investigated to evaluate the adsorption capacity. The equilibrium data of graphene oxide adsorption was better represented by the Langmuir isotherm and was achieved within 60 minutes. The results showed that GO has potential to be an important adsorbent for lead removal. In the future, GO might be imbedded as adsorbent in the membrane fabrication for wastewater treatment.
Commercial titanium dioxide Degussa P25 (TiO2) was used for the adsorption of reactive red 120
(RR120) dye in a batch system. The optimization functions such as solution pH (3-12), adsorbent dosage (0.02 g-1.2 g), and initial dye concentration (30-400 mg/L) were studied. The equilibrium adsorption data for RR120 dye was analyzed by two types of isotherm models which are Langmuir and Freundlich models. The adsorption at equilibrium showed a better fit for linear Langmuir isotherm with the adsorption capacity, qmax of 18.62 mg/g at 303 K. The adsorption kinetic was well-described by pseudosecond order model. TiO2 showed a decent outcome due to the ability to adsorb target pollutants with theadded advantage of providing large hydroxyl groups (OH) on the surface of TiO2 so that pollutants can be adsorbed by interacting on the surface of OH.
Cross-linked chitosan-epichlorohydrin was prepared for the adsorption of Reactive Red 4 (RR4).
Response surface methodology (RSM) with 3–level Box-Behnken design (BBD) was employed to
optimize the RR4 dye removal efficiency from aqueous solution. The adsorption key parameters that were selected such as adsorbent dose (A: 0.5 – 1.5 g), pH (B: 4 – 10) and time (30 – 80 min). The F-value of BBD model for RR4 removal efficiency was 185.36 (corresponding p-value < 0.0001). The results illustrated that the highest RR4 removal efficiency (70.53%) was obtained at the following conditions: adsorbent dose (1.0 g), pH 4 and time of 80 min.
This study tested the technical feasibility of pyrite and/or persulfate oxidation system for arsenic (As) removal from aqueous solutions. The effects of persulfate on As removal by the pyrite in the integrated treatment were also investigated. Prior to the persulfate addition into the reaction system, the physico-chemical interactions between As and the pyrite alone in aqueous solutions were explored in batch studies. The adsorption mechanisms of As by the adsorbent were also presented. At the same As concentration of 5 mg/L, it was found that As(III) attained a longer equilibrium time (8 h) than As(V) (2 h), while the pyrite worked effectively at pH ranging from 6 to 11. At optimum conditions (0.25 g/L of pyrite, pH 8.0 and 5 mg/L of As(III) concentration), the addition of persulfate (0.5 mM) into the reaction promoted a complete removal of arsenic from the solutions. Consequently, this enabled the treated effluents to meet the arsenic maximum contaminant limit (MCL) of <10 μg/L according to the World Health Organization (WHO)'s requirements. The redox mechanisms, which involved electron transfer from the S22- of the pyrite to Fe3+, supply Fe2+ for persulfate decomposition, oxidizing As(III) to As(V). The sulfur species played roles in the redox cycle of the Fe3+/Fe2+ of the pyrite by giving its electrons, while the As(III) oxidation to As(V) was attributed to the pyrite. Overall, this work reveals the applicability of the pyrite as an adsorbent for water treatment and the importance of persulfate addition to promote a complete As removal from aqueous solutions.
The emergence of the aluminium recycling industry has led to an increase in aluminium-containing wastewater discharge to the environment. Biological treatment of metal is one of the solutions that can be provided as green technology. Screening tests showed that Brochothrix thermosphacta and Vibrio alginolyticus have the potential to remove aluminium from wastewater. Brochothrix thermosphacta removed up to 49.60%, while Vibrio alginolyticus was capable of removing up to 59.72% of 100 mg/L aluminium in acidic conditions. The removal of aluminium by V. alginolyticus was well fitted with pseudo-first-order kinetics (k1 = 0.01796/min), while B. thermosphacta showed pseudo-second-order kinetics (k2 = 0.125612 mg substrate/g adsorbent. hr) in the process of aluminium removal. V. alginolyticus had a higher rate constant under acidic conditions, while B. thermosphacta had a higher rate constant under neutral pH conditions.
The biodegradability and safety of the bioflocculants make them a potential alternative to non-biodegradable chemical flocculants for wastewater treatment. However, low yield and production cost has been reported to be the limiting factor for large scale bioflocculant production. Although the utilization of cheap nutrient sources is generally appealing for large scale bioproduct production, exploration to meet the demand for them is still low. Although much progress has been achieved at laboratory scale, Industrial production and application of bioflocculant is yet to be viable due to cost of the production medium and low yield. Thus, the prospects of bioflocculant application as an alternative to chemical flocculants is linked to evaluation and utilization of cheap alternative and renewable nutrient sources. This review evaluates the latest literature on the utilization of waste/wastewater as an alternative substitute for conventional expensive nutrient sources. It focuses on the mechanisms and metabolic pathways involved in microbial flocculant synthesis, culture conditions and nutrient requirements for bioflocculant production, pre-treatment, and also optimization of waste substrate for bioflocculant synthesis and bioflocculant production from waste and their efficiencies. Utilization of wastes as a microbial nutrient source drastically reduces the cost of bioflocculant production and increases the appeal of bioflocculant as a cost-effective alternative to chemical flocculants.
Microwave vacuum pyrolysis of palm kernel shell was examined to produce engineered biochar for application as additive in agriculture application. The pyrolysis approach, performed at 750 W of microwave power, produced higher yield of porous biochar (28 wt%) with high surface area (270 cm2/g) compared to the yield obtained by conventional approach (<23 wt%). Addition of the porous biochar in mushroom substrate showed increased moisture content (99%) compared to the substrate without biochar (96%). The mushroom substrate added with biochar (150 g) was optimal in shortening formation, growth, and full colonization of the mycelium within one month. Using 2.5% of the biochar in mushroom substrate desirably maintained the optimum pH level (6.8-7) during the mycelium colonization period, leading to high mycelium growth (up to 91%) and mushroom yield (up to 280 g). The engineered biochar shows great potential as moisture retention and neutralizing agent in mushroom cultivation.
Rising of temperature in conjunction with acidification due to the anthropogenic climates has tremendously affected all aquatic life. Small changes in the surrounding environment could lead to physiological constraint in the individual. Therefore, this study was designed to investigate the effects of warm water temperature (32 °C) and low pH (pH 6) on physiological responses and growth of hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) juveniles for 25 days. Growth performance was significantly affected under warm water temperature and low-pH conditions. Surprisingly, the positive effect on growth was observed under the interactive effects of warm water and low pH exposure. Hybrid grouper exposed to the interactive stressor of warm temperature and low pH exhibited higher living cost, where HSI content was greatly depleted to about 2.3-folds than in normal circumstances. Overall, challenge to warm temperature and low pH induced protein mobilization as an energy source followed by glycogen and lipid to support basal metabolic needs.
A sequencing batch reactor (SBR) seeded with flocculated sludge and fed with synthetic wastewater was operated for an enhanced biological phosphorus removal (EBPR) process. Eight weeks after reactor startup, sludge granules were observed. The granules had a diameter of 0.5 to 3.0 mm and were brownish in color and spherical or ellipsoidal in shape. No significant change was observed in sludge granule size when operational pH was changed from 7 to 8. The 208-day continuous operation of the SBR showed that sludge granules were stably maintained with a sludge volume index (SVI) between 30 to 55 mL/g while securing a removal efficiency of 83% for carbon and 97% for phosphorus. Fluorescent in situ hybridization (FISH) confirmed the enrichment of polyphosphate accumulating organisms (PAOs) in the SBR. The observations of sludge granulation in this study encourage further studies in the development of granules-based EBPR process.
Solid waste comprised of a grass clippings mixture was decomposed using a locally-made compost bin in Pulau Pinang, Malaysia, to eliminate challenges associated with improper waste disposal. Bulk density, pH, moisture content, nutrients content, nitrogen (N), phosphorus (P), potassium (K), iron (Fe), zinc (Zn), copper (Cu) and carbon/nitrogen (C/N) ratio were determined over 77 days. A 34% reduction in compost bin volume was observed and bulk density and pH were also reduced from 732 to 482 kg m(-3) and 7.82 to 8.41, respectively, indicating fairly good performance. The final moisture content and C/N ratio were 44.06% and 14 : 1, respectively, and the results also showed that the presence of nutrients and heavy metals in the final compost were within acceptable limits for use as a soil conditioner. Final concentrations of N, P and K were 347 mg kg(-1), 510 mg kg(-1) and 14.8 g kg(-1) and for heavy metals, Fe, Zn and Cu were 5308, 300 and 20 mg kg(-1), respectively, which considerably assisted in the decomposition process. Processed waste materials from the bin were shown to be excellent organic fertilizers with over 75% germination index for seeds grown into bean sprouts in 72 h. An improved bin design to eliminate greenhouse gas emission into the environment is suggested.
The current study investigated the effects of S2O8(2-) and S2O8(2-)/H2O2 oxidation processes on the biodegradable characteristics of an anaerobic stabilized leachate. Total COD removal efficiency was found to be 46% after S2O8(2-) oxidation (using 4.2 g S2O8(2-)/1g COD0, at pH 7, for 60 min reaction time and at 350 rpm shaking speed), and improved to 81% following S2O8(2-)/H2O2 oxidation process (using 5.88 g S2O8(2-) dosage, 8.63 g H2O2 dosage, at pH 11 and for 120 min reaction time at 350 rpm). Biodegradability in terms of BOD5/COD ratio of the leachate enhanced from 0.09 to 0.1 and to 0.17 following S2O8(2-) and S2O8(2-)/H2O2 oxidation processes, respectively. The fractions of COD were determined before and after each oxidation processes (S2O8(2-) and S2O8(2-)/H2O2). The fraction of biodegradable COD(bi) increased from 36% in raw leachate to 57% and 68% after applying S2O8(2-) and S2O8(2-)/H2O2 oxidation, respectively. As for soluble COD(s), its removal efficiency was 39% and 78% following S2O8(2-) and S2O8(2-)/H2O2 oxidation, respectively. The maximum removal for particulate COD was 94% and was obtained after 120 min of S2O8(2-)/H2O2 oxidation. As a conclusion, S2O8(2-)/H2O2 oxidation could be an efficient method for improving the biodegradability of anaerobic stabilized leachate.
Zingiber zerumbet Smith is an important herb that contains bioactive phytomedicinal compound, zerumbone. To enhance cell growth and production of this useful compound, we investigated the growth conditions of cell suspension culture. Embryogenic callus generated from shoot bud was used to initiate cell suspension culture. The highest specific growth rate of cells was recorded when it was cultured in liquid Murashige and Skoog basal medium containing 3% sucrose with pH 5.7 and incubated under continuous shaking condition of 70 rpm for 16 h light and 8 h dark cycle at 24°C. Our results also revealed that the type of carbohydrate substrate, light regime, agitation speed, and incubation temperature could affect the production of zerumbone. Although the zerumbone produced in this study was not abundant compared to rhizome of Z. zerumbet, the possibility of producing zerumbone during early stage could serve as a model for subsequent improvement.
Two strains ofRhizopus rhizopodiformis that produced lipases in broth culture were isolated. Maximum lipase production (23 U/ml) was obtained after 72 h culture. Both the crude lipases were stable at 50°C for 30 min and at 45°C for 24 h. Maltose was the best carbon source and peptone the best nitrogen source for the production of lipases. Only glycerol and lecithin stimulated lipase production further.
The aim of this study was to investigate the effect of cut type and pulsed light (PL) fluence on microbiological stability and quality of fresh-cut cantaloupes. Fresh-cut cantaloupes with various cut types (cuboid, triangular prism and sphere) were treated with PL technology at 6 J/cm(2). Samples were exposed to PL treatment at fluences of 2.7, 7.8, 11.7 and 15.6 J/cm(2) followed by storage at 4 ± 1 °C for 28 days. Microbiological quality, headspace composition, firmness, colour, pH, titratable acidity, total soluble solids, total phenolic content and ascorbic acid content of fresh-cut cantaloupes were determined. Spherical shape was found to be the most suitable shape for PL treatment of fresh-cut cantaloupes due to its significantly lowest (p ≤ 0.05) microbial counts before and after the PL treatment. No significant (p > 0.05) effect was observed for firmness, colour, total soluble solids and total phenolic content of fresh-cut cantaloupes throughout the storage study. Pulsed light treatment using 7.8 J/cm(2) was the best for extending shelf life of fresh-cut cantaloupes with extension of 8 days longer at 4 ± 1 °C compared to the control while maintaining the ascorbic acid content. In conclusion, PL treatment is a potential technique for extending the shelf life of fresh-cut cantaloupes by inactivating microorganisms without compromising the nutritional value.