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"Agricultural waste hasincreased colossally with development in agricultural production causing environmentalnuisance and degradation. Utilization of coconut husks, one of such type of waste, as a biosorbent for polluted surface water treatment, wasconsidered in this study. Polluted surface water was gently passed through twosimilar columns loaded with 100 and 200 g of coconut husk char respectively.The treated water samples collected after 30, 60, 90, 120 and 150 mins wereexamined for SO42-, NO3- and PO43-ions concentration. Removal efficiency for SO42-, NO3-and PO43- ions on 100 g coconut husk char after 150mins detention time were 70, 78 and 91% respectively. Freundlich isotherm modelgave a better description of the data (R2 > 0.96). Sorption datawas well described by second order pseudo kinetics (R2 >0.85). An amount of 100 g of the biosorbenthas astrong affinity for these types of ion removal in contaminated water. Coconut huskchar as a biosorbentis a panacea to significant concentrations of polyatomic ions in polluted surface water."

"Agricultural waste has increased colossally with development in agricultural production causing environmental nuisance and degradation. Utilization of coconut husks, one of such type of waste, as a biosorbent for polluted surface water treatment, was considered in this study. Polluted surface water was gently passed through two similar columns loaded with 100 and 200 g of coconut husk char respectively. The treated water samples collected after 30, 60, 90, 120 and 150 mins were examined for SO42-, NO3- and PO43- ions concentration. Removal efficiency for SO42-, NO3- and PO43- ions on 100 g coconut husk char after 150 mins detention time were 70, 78 and 91% respectively. Freundlich isotherm model gave a better description of the data (R2 > 0.96). Sorption data was well described by second order pseudo kinetics (R2 > 0.85). An amount of 100 g of the biosorbent has a strong affinity for these types of ion removal in contaminated water. Coconut husk char as a biosorbent is a panacea to significant concentrations of polyatomic ions in polluted surface water."

"The gas diffusion layer (GDL) is one of the critical components of a proton exchange membrane fuel cell (PEMFC). It is generally made of a fossil-fuel-based carbon material. In this study, carbon composite paper (CCP) for GDL was prepared by using carbon material obtained from coconut coir. To obtain the CCP, 80 wt% carbon material from the coconut coir and 20 wt% polymer binder (ethylene vinyl acetate and polyethylene glycol) were mixed in xylene solvent at 100°C, cast on molded glass, and then rolled. The carbon material consists of a mixture of carbon fibers (length: 2 mm) and powders (size: 74 µm). Subsequently, the CCP was treated with polytetrafluoroethylene solution (10 wt%). The physical properties of the CCPs, such as through-plane electrical conductivity, porosity, density, and hydrophobic properties, were investigated. Scanning electron microscopy and energy-dispersive spectroscopy mapping were used to analyze the morphology and polytetrafluoroethylene (PTFE) distribution in the CCP. The through-plane conductivity test showed that CCP with 70 wt% carbon fiber, 10 wt% carbon powder, and 20 wt% polymer was the optimum sample, and it showed the highest electrical conductivity of 2.22 S cm-1. The physical properties of PTFE-treated CCP, such as porosity, density, and contact angle, were almost similar to that of commercial carbon paper used as a GDL. Therefore, the CCP prepared from coconut coir can be applied as a GDL in a PEMFC."

"The kinetics of aluminumleaching from sludge solid waste (SSW) using hydrochloric acid at differentleaching temperatures (30-90°C) was studied. A mathematical model was developed based on ashrinking core model by assuming first-order kinetics mechanisms for leachingand an equilibrium linear at the solid-liquidinterface. The proposed model is suited to fit experimental data with threefitting parameters and to simulate the leaching of aluminum from SSW, which wasvalidated with the mass transfer coefficient (kc, cm/s),diffusion coefficient (De,cm2/s), and reaction rate constants (k, cm/s). The evaluated kc,De, and k are expected to follow an increasingtrend with increasing temperature. The correlation coefficient ≥ 0.9795, theroot mean square error ≤ 0.399, the mean relative deviation modulus ≤ 6.415%,and the value of activation energy is 13.27 kJmol-1. The proposed model could describe the kinetics ofaluminum leaching from the SSW DWT in accordance with test parameters andrelevant statistical criteria. Valuable information on the results of this workcan be given for the purposes of the simulation, optimization, scaling-up, anddesign of the leachingprocess."

"Rice husk is one of themost abundant biomass wastes in Indonesia. One way to convert it into analternative source of energy is biomass gasification. This is a thermochemicalprocess which converts biomass feedstock into fuel gas or chemical feedstockgas (producer gas). The gasification type which is developed in this study isfixed bed downdraft type due to its low tar content and compatibility inmicroscale implementation. One major problem with the implemented biomassgasification reactor was ruggedness of the partial oxidation process due to theabsence of air in the reactor?s middle section, which consequently affected thepyrolysis zone. Several experiments were conducted previously using coconutshells and rice husks as solid feedstock, where an equivalence ratio (ER) of0.4 was obtained. Therefore, in order to optimize the pyrolysis zone, themodification conducted involves adding a circular air intake into the gasifier.Experiments were conducted in a pyrolysis temperature range of 300?700oCwith ER variation of 0.19, 0.24, 0.27 and 0.31. The results show that a goodquality producer gas is produced at an ER value of 0.24. This value shows apromising result because the ER value of biomass gasification standard is 0.25."

"Flotation is animportant process in mining industries. This process employs the bubble andhydrophobic properties of a particle to separate valuable mining particles fromimpurities. The most important phenomenon in determining flotation efficiencyis the bubble-particle interaction; therefore, understanding this phenomenon isvery important. The aim of this research is to study the mechanism ofbubble-particle interactions with and without the addition of a collector. Theexperimental setup consists of a water container, bubble generator, particlefeeding system, and an image capturing system. The water container is made fromtransparent material of a size large enough so that the wall?s effects onbubbles and particles can be neglected. Air bubbles are generated by a bubblegenerator which consists of a small nozzle and programmable syringe pump. Ahigh speed video camera and halogen lamp backlighting system are used as imagecapturing devices. Observation of the images reveals that bubble-particleinteraction follows the stages of bubble-particle collision, particle attachedto the bubble, and particle detached from the bubble. The addition of acollector to the liquid affects the bubble-particle interactions."

"Ballast is one of themain structures for the railway tracks. It can resist the lateral movementunder dynamic loading transferred by the passing trains with repeatedly. Undersome circumstances, ballast can suffer degradation or breakdown due to therepeated loading and maintenance. Ballast is easily exposed to the weatherbecause it is laid on the track. Acid rain affects the performance of therailway track near the industrial and urbanarea. As a result, it starts to foul and the small chips from ballast filledthe void, as well as reduce the shear strength of ballast particles. Thissituation can contribute into the increasing of maintenance frequency andcosting. This paper examines the potential of rubber inclusions in increasingthe shear resistance of rubber-ballast composites in simulated water and acid soakedconditions with several configuration. This lab-based exploratory work is only static load simulation in conventional shear boxsetup measuring 60 mm × 60 mm.The aggregates size is 10 times smaller than actual size of ballast. In orderto identify the shear resistance deterioration of rubber-aggregates mixtureunder poor drainage conditions by soaked a batch of aggregates in water andacid solution for 2 weeks to simulate accelerated weathering effects. The shearresistance did not rise dramatically with the rubber reinforcement. Thissusceptible shear strain plots indicate ductile behaviour on theaggregates-rubber composites. This is evident by the linear rise of shearstress with strain up to approximately 10% for the control samples (CS) untilit reaches a constant value. Note that all the specimens including CS are in aloose state during the testing because there were no tamping been applied onthe samples. Overall the circular patch (CP) specimen was the most favourablethan the other configurations. Both mechanisms contributed to the reducedoverall subsistence, accompanied by an increase in the shear resistance. Theinclusion of rubber elements apparently prevented the dilation of the granularmaterial when approaching the shear failure and the reducing the settlement."

"The main problem with the slurry process is the difficulty in recovering the photocatalyst nanoparticle from water following purification. An alternative solution proposed the photocatalyst be immobilized on magnetic carriers, which would allow them to be recollected from the water suspension following treatment using an external magnetic field. Magnetically photocatalyst composites were prepared using simple heteroagglomeration by applying attractive electrostatic forces between the nanoparticles with an opposite surface charge. The Fe3O4/SiO2/TiO2 photocatalysts were synthesized in an aqueous slurry solution containing Fe3O4/SiO2 and TiO2 nanoparticles under pH 5 conditions. Meanwhile, Fe3O4/SiO2 was prepared by a simple procedure via a coprecipitation of iron(II) and iron(III) ion mixtures in ammonium hydroxide and was leached by sodium silicate. The synthesized samples were investigated to determine the phase structure, the magnetic properties, and the morphology of the composites by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and transmission electron microscopy (TEM), respectively. The results indicated that the composites contained anatase and rutile phases and exhibited a superparamagnetic behavior. Fe3O4/SiO2 particles, which were of the aggregation spherical form at 20 nm in size, were successfully attached onto the TiO2 surface. The catalytic activity of Fe3O4/SiO2/TiO2 composites was evaluated for the degradation of methylene blue under ultraviolet (UV) irradiation. The presence of SiO2 as a barrier between Fe3O4 and TiO2 is not only improves the photocatalytic properties but also provides the ability to adsorb the properties on the composite. The Fe3O4/SiO2/TiO2 (50% containing TiO2 in composite) were able to eliminate 87.3% of methylene blue in water through the adsorption and photocatalytic processes. This result is slightly below pure TiO2, which is able to degrade 96% of methylene blue. The resulting Fe3O4/SiO2/TiO2 composite exhibited an excellent ability to remove dye from water and it is easily recollected using a magnetic bar from the water. Therefore, they have high potency as an efficient and simple implementation for the dye effluent decolorization of textile waste in slurry reactor processes."

"The findings of numerousstudies on the responses of stream quality indicatorsto different levels of watershed development have been integrated into an impervious cover model. The focus on one development stressor, namely theimpervious cover, allows the decision makers to use the impervious cover model as a watershed planning toolto forecast stream response. In evaluating streamquality, the studies used various indicators such as pollutant loads, habitatquality, aquatic species diversity and abundance, and others. This studyaims to test the applicability of the imperviouscover model as a tool to set the threshold of catchment area developmentbased on the targeted water quality index. Themodel is represented by a linear relationship between the water quality indexas a response variable and catchment area imperviousness as an explanatoryvariable. The study area is an urbanized catchment area of a cascade-pondsystem located at the campus of Universitas Indonesia, Depok, West Java.Estimation of catchment area imperviousness is based on digital globe imageryand digitized based on identified rooftops. The water quality data to computethe water quality indices are collected from previous studies and relatedreports. The targeted water quality index is determinedbased on water use suitability referring to the Indonesian governmentregulation number 82/2001. Basedon the available data, an increasing tendency of temporal variation ofcatchment area imperviousness for each pond can be recognized, while waterquality index of each pond tends to decrease over time. In accordance with landcover distribution, spatial tendency indicates that imperviousness isdecreasing in downstream direction, while water quality index is increasing indownstream direction, in line with the characteristics of cascade ponds. Theresults demonstrate that despite the fact that the available data are verylimited, it is possible to use the linear relationship between catchment areaimperviousness and water quality index as a tool to set the threshold forfuture development on the catchment area of the cascade-pond system at thecampus of Universitas Indonesia with a minimum water quality index suitablejust for recreation activities."

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