Nitric Oxide Reduction with Hydrogen over Carbon-Supported Copper-Iron Oxides Catalysts

Nitric oxide (NO) is an air pollutant generated during fuel combustion which is responsible for ground-level ozone, acid rain and smog formation. Current abatement technologies include reducing NO to nitrogen (N2) in the presence of a reductant, usually ammonia, and a catalyst. Replacing ammonia with a less-toxic reductant such as hydrogen (H2-SCR) requires the utilization of expensive precious metal as a catalyst supported on metal oxides. This study aims to evaluate the potential use of hydrogen as a renewable reductant; activated carbon as a sustainable catalyst support; and less-precious metals as a catalyst to selectively convert NO to N2. Mono- and bimetallic oxide catalysts were synthesized via incipient wetness method using copper, iron and manganese oxides supported over palm kernel shell activated carbon. Copper-based catalysts were proven to totally convert NO (100 %) in an oxidizing condition starting at 250 °C, while co-impregnating with iron oxide (PKSFeCu) improved N2 selectivity (eg. from 80 to 100 % at 200 °C) as well as lowering the carbon combustion rate (eg. from 3.1 to 2.3 μmol CO+CO2/s). The catalysts were characterized via elemental and metal content analyses, nitrogen adsorption-desorption, ammonia-temperature-programmed desorption, Fourier-Transform infra-red spectroscopy, hydrogen-temperature-programmed reduction, thermogravimetric analysis, and NO-temperature-programmed desorption. The conversion and selectivity were found to correlate strongly with the catalyst reducibility and acidity. Kinetic experiments revealed that the rate of reaction for H2-SCR using PKSFeCu obeys a power rate law with an order of 0.82 with respect to NO concentration. The stability test showed that the catalyst is susceptible to changes in physical properties under prolonged exposure to high temperatures and feed gas disturbance. Therefore, improvements in terms of catalyst stability should be the main focus of future work for this sustainable H2-SCR system to become an attractive alternative to NH3-SCR

VALIDITAS DAN KEPRAKTISAN LEMBAR KEGIATAN PESERTA DIDIK (LKPD) BERBASIS GUIDED DISCOVERY PADA MATERI GENETIKA UNTUK SMA KELAS XII

Materi genetika merupakan materi yang sulit dipahami karena memuat konsep yang terdiri atas beberapa tahapan rumit dan kompleks. Namun dalam mempelajarinya, peserta didik menggunakan LKPD berisi ringkasan dan beberapa pertanyaan yang belum melatihkan untuk menemukan konsep secara mandiri. Oleh karena itu, diperlukan LKPD yang dapat membantu peserta didik untuk menemukan konsep secara mandiri. Penelitian ini bertujuan untuk menghasilkan LKPD berbasis guided discovery pada materi genetika untuk SMA kelas XII yang valid dan praktis. Penelitian ini merupakan penelitian pengembangan dengan model pengembangan 4D (Define, Design, Develop, dan Disseminate) tanpa tahap Disseminate. Validitas LKPD ditinjau berdasarkan validasi pakar pendidikan dan pakar materi genetika. Kemudian, LKPD diujicobakan secara terbatas pada 20 peserta didik kelas XII SMA Negeri 1 Sidayu pada bulan Februari 2018 untuk diketahui kepraktisannya. Kepraktisan LKPD ditinjau dari aktivitas peserta didik oleh pengamat yang merupakan mahasiswa S1 pendidikan Biologi. Hasil validasi LKPD diperoleh modus sebesar 3,5 yang termasuk dalam kategori sangat valid. Hasil pengamatan aktivitas peserta didik diperoleh persentase kemunculan sebesar 100%. Berdasarkan hasil penelitian dapat disimpulkan bahwa LKPD berbasis guided discovery pada materi substansi genetika yang dikembangkan dinyatakan sangat valid dan sangat praktis. Kata kunci: validitas, kepraktisan, LKPD, guided discovery, materi genetik

Characterization of Calcium Hydroxide (CH) crystals in Nano Modified Binder (NMB)

With the advent of nanotechnology, such nano scale materials have been developed for the application in binding material namely cement.A new synthetic material, namely Nano-SiO2(nS), has been produced and available in the market. It is based on silica particles of 5-50 nm which is much smaller than those of silica fume (microsilica) with particles of 0.1-1 μm. Previous studies have shown that due to the very high specific surface area (80-1000 m2/g) and the spherical shape of silica particles,it can potentially enhance the performance of cement mainly due to its reaction with calcium hydroxide (CH) to develop more of the strength-carrying compound in cement structure namely calcium silica hydrate (C-S-H). This reaction namely pozzolanic reaction is crucial in the mitigation of efflorescence by its relation to CH leaching. The early hydration behaviour of a Nano Modified Binder (NMB) that hypothetically affects efflorescence has been investigated through physicochemical characterization namely Puddle Test (PT), Standard Chemical Method (SCM), Compressive Strength Test (CS), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). NMB mortar samples were prepared with water-to-cement ratio (w/c) of 0.50. nS of 10-20 nm particle size was used as 2%, 3% and 5% replacement of cement by weight. Samples were cured at room temperature (32o C) and average relative humidity (90%). Powdered and polished samples were prepared and tested at 28 days of binder hydration. Results from CS, XRD analysis and SEM images show that compare to conventional binder, NMB exhibited a lesser efflorescence where validation from CS, XRD analysis and SEM images show the evidence of the pozzolanic reaction

Effect of NaOH Treated Oil Palm Empty Fruit Bunch (OPEFB) on Adsorption of Cd (II) Under Acidic Condition

Adsorption is an effective way of extracting heavy metal ions from aqueous solutions. Alkali treatment is a chemical modification method that is influenced by concentration and time. The study aims to investigate the effect of NaOH treatment of OPEFB on Cd (II) adsorption under acidic condition. The alkali treatment was done by varying the concentration of NaOH (0.1 M, 0.5 M, and 1.0 M) and the immersion time (12 h and 24 h). SEM images confirmed the existence of pores on the treated OPEFB in comparison with the raw OPEFB. Characterization of treated adsorbent using FTIR resulted in a change of functional groups peak’s position such as hydroxyl and carboxyl groups after the alkali treatment, which might involve Cd (II) adsorption. OPEFB treated with 1.0 M NaOH and 24 h immersion time showed the highest Cd (II) removal under acidic condition (pH 4). All the NaOH treated OPEFB showed an increment in adsorption efficiencies compared to raw OPEFB, suggesting that this treated biomass has a potential for application as an adsorbent for the removal of Cd (II) from wastewate

Oil palm biomass-based activated carbons for the removal of cadmium-a review

Serious water pollution due to climate change as the consequences of non-ecological wastewater treatment and unsustainable agricultural activities had emerged water scarcity problem. The utilization of oil palm biomass into cadmium adsorbent could play a role in killing two birds with one stone, which is to solve the oil palm biomass disposal issue and cadmium pollution issue. The adsorbent modifications discussed in this review focused on furnace heating and microwave heating as well as the combined methods with chemical activating agents. Among the modification methods, the output of chemical activation followed by microwave-induced irradiation of palm kernel shells (PKS) produced activated carbon with high specific surface area (854.42 m2 /g) and high adsorption capacity, qmax (227.27 mg/g). This review is to provide a comprehensive understanding of cadmium adsorption mechanisms and up-to-date progress of modification technologies for different types of oil palm biomass

Characterization of early pozzolanic reaction of Calcium Hydroxide and Calcium Silicate Hydrate for Nanosilica modified cement paste.

This study intends to investigate the early pozzolanic reaction of Nanosilica (nS) modified cement paste (NMCP) by the characterization technique of Calcium Hydroxide (CH) and Calcium Silicate Hydrate (C-S-H ) using Fourier Transform Infrared Spectroscopy (FT-IR). NMCP samples were prepared with water-binder ratio of 0.50. nS of 5-15nm particle size were used as 1%, 3% ,5% ,7% and 10% replacement of cement by weight. All samples were cured in the concrete laboratory at daily room temperature (T) and relative humidity (RH) in the range of 18-28oC and 65-90%, respectively. Powdered samples were prepared and tested at day 1,7,21 and 28. It was found that characterization technique used were able to give satisfactory qualitative indication of pozzolanic reactivity of NMCP by the presence and absence of C-S-H and C-H that can indicate which replacement has higher pozzolanicity. NMCP exhibited a higher pozzolanic reactivity compare to conventional cement paste by which cement performance was enhanced

Characterization of early pozzolanic reaction of Calcium Hydroxide and Calcium Silicate Hydrate for Nanosilica modified cement paste.

This study intends to investigate the early pozzolanic reaction of Nanosilica (nS) modified cement paste (NMCP) by the characterization technique of Calcium Hydroxide (CH) and Calcium Silicate Hydrate (C-S-H ) using Fourier Transform Infrared Spectroscopy (FT-IR). NMCP samples were prepared with water-binder ratio of 0.50. nS of 5-15nm particle size were used as 1%, 3% ,5% ,7% and 10% replacement of cement by weight. All samples were cured in the concrete laboratory at daily room temperature (T) and relative humidity (RH) in the range of 18-28oC and 65-90%, respectively. Powdered samples were prepared and tested at day 1,7,21 and 28. It was found that characterization technique used were able to give satisfactory qualitative indication of pozzolanic reactivity of NMCP by the presence and absence of C-S-H and C-H that can indicate which replacement has higher pozzolanicity. NMCP exhibited a higher pozzolanic reactivity compare to conventional cement paste by which cement performance was enhanced

Passive Nitrogen Oxides Removal from a Diesel-engine Exhaust Gas Using a Biomass-carbon Catalyst

Nitrogen oxides (NOx) removal from a diesel-engine exhaust gas requires the utilization of ammonia/urea as a reducing agent (SCR) which arose environmental concerns over the use of this chemical. Therefore, this study explored the potential of using a sustainable NOx removal system by replacing ammonia with intrinsic reductants present in the exhaust gas, such as hydrocarbons and carbon monoxide, and by application of cost-effective carbon-supported transitional metals catalyst. Copper-cerium catalyst supported over palm kernel shell activated carbon (Cu-Ce/PKS) was synthesized via deposition-precipitation method. The characterization shows that the catalyst has a considerably high surface area (though lower than the support). The high NOx removal by Cu-Ce/PKS in a passive catalytic reaction is attributable to the surface area provided by the carbon support, the low copper reducibility which leads to the low optimum operating temperature, and the synergistic effect between Cu and Ce which resulted in the wide temperature window at low-temperature range. It is concluded that Cu-Ce supported over palm kernel shell activated carbon can be further developed to reduce NOx in a passive catalytic removal for a sustainable and cost-effective SCR system

Ag+ colorimetric sensor based on graphene oxide/nano-platinum composite

With the development of society, pollution accidents occur more frequently, and the efects of toxic substances containing silver on human health and environment are increasingly extensive. Therefore, the real-time on-site monitoring of silver ions is urgently needed. Based on the catalase-like properties of graphene/nano-platinum composites and the coupling efect between Pt and Ag+, a simple, unlabeled colorimetric sensing method is proposed to achieve the quantitative detection of Ag+. Under optimal conditions, the detection range of Ag+ by this colorimetric sensing method is 0.5–1000 μM, and the detection limit is 0.5 μM, which is lower than the previously reported detection limit of unlabeled Ag+ colorimetric sensing method, showing higher sensitivity and detection range. Under the same conditions, the sensor has almost no response to interference ions, showing good specifc recognition ability. In addition, the colorimetric sensing method can be used to detect Ag+ in actual water samples, serving as a new paradigm for visual detection of Ag+

Adsorption Isotherm of Chromium (VI) into Zncl2 Impregnated Activated Carbon Derived by Jatropha Curcas Seed Hull

Hexavalent chromium is carcinogenic and should be removed from industrial wastewater before discharged into water resources. Adsorption by using activated carbon from biomass is an economic and conventional way on removing the heavy metal ions from wastewater. In this research, activated carbon is synthesized from Jatropha curcas L. seed hull through chemical activation with ZnCl2 and carbonized at 800 °C (JAC/ZnCl2). The activated carbon has been characterized using FTIR, SEM-EDX, BET and CHNS-O analyzer. Adsorption isotherms have been analysed using Langmuir and Freundlich models to determine its removal mechanism. The maximum adsorption capacity of Cr (VI) metal ions onto JAC/ZnCl2 activated carbon is 25.189 mg/g and following Langmuir isotherm model which is monolayer adsorption