Varying Contact Time Research Articles

Synthesis of mesoporous silica and chitosan-coated magnetite nanoparticles for heavy metal adsorption from wastewater

The use of magnetic nano-sized adsorbents for the removal of heavy metals from water possesses significant potential in water remediation sector. The goal of this study was to develop economically feasible magnetite nanoparticles with an appropriate surface functionalization that will simultaneously provide adsorption efficiency, hydrophilicity, and recyclability without compromising magnetic properties. Magnetite nanoparticles (MNPs) were produced via the thermal decomposition process of iron oleate precursor due to monodispersity provided by this method. The particles were coated with mesoporous silica layers by utilizing cetyltrimethylammonium bromide (CTAB) as the surfactant. The coated particles were subjected to chitosan coating by stirring in chitosan solution. The success of the coating process was confirmed by performing Fourier-transform infrared spectroscopy (FTIR) analysis between each step. The particles were used as an adsorbent in heavy metal salts solutions of known concentrations. The adsorption study was conducted with varying contact time and initial concentration and the data was analyzed for fitting to pseudo 1st order and pseudo 2nd order kinetic models, and the Langmuir and Freundlich isotherm models to determine the adsorption characteristics. The kinetic model and isotherm fitting indicted that the adsorption occurred by monolayer chemical adsorption. The developed adsorbent exhibited a satisfactory adsorption capacity of 150.33 mg/g and 126.26 mg/g for Pb2+ and Cd2+ respectively which is a good indication for further exploration and analysis.

Relationship between Objective and Subjective Fatigue Monitoring Tests in Professional Soccer.

Studying fatigue is challenging because it is influenced by physiological, psychological, and sociological states. Fatigue can be assessed objectively or subjectively, but the literature has difficulty understanding how an analytical test relates to a response via a questionnaire. Thus, the purpose of this study was to evaluate the relationships between objective fatigue variables (Squat Jump (SJ) and Countermovement Jump (CMJ)) measured on day-2 to the game and subjective fatigue (Rating Perceived Exertion (RPE) measured on day-3 to the game and Hooper Index (HI) measured on day-2). The sample comprised 32 professional football players from the First Portuguese League aged 25.86 ± 3.15 years. The Spearman correlations and regression analyses were used to study the relationships between the variables. The results showed statistically significant (p < 0.05) but small correlations (0.113-0.172) between several objective metrics and the subjective metrics evaluated. In addition, we found two weak models with statistical significance (p < 0.05) between the dependent objective variables (contact time, height, and elasticity index) and the HI (R2 = 3.7%) and RPE (R2 = 1.6%). Also, nine statistically significant (p < 0.05) but weak models were observed between the subjective dependent variables (HI and RPE) and contact time (R2 = 1.8-2.7%), flight time (R2 = 1.1-1.9%), height (R2 = 1.2-2.3%), power (R2 = 1.4%), pace (R2 = 1.2-2.1%), and elasticity index (R2 = 1.6%). In conclusion, objective and subjective fatigue-monitoring tests in professional soccer do not measure identical but rather complementary aspects of fatigue, and therefore, both need to be considered to gain a holistic perspective.

Comparison study of COD adsorption on bentonite-based nanocomposite materials in landfill leachate treatment: Characterization, Isotherms, Kinetics and Regeneration

The COD removal from landfill leachate using bentonite-based nanocomposites prepared using different modifiers has been investigated. Different techniques including FE-SEM, XRD, FTIR, TGA and Zeta potential have been utilized for characterization of nanocomposites (NCs). The independent variables includingNCs dose, pH and contact time are studied for COD removal efficiency. The optimal values are obtained to be a NCs dose of 40 g/L, pH of 3.00, and a contact time of 20 min for maximized COD removal efficiencies of 67.90, 71.30 and 52.00% using Arg/CTS-BEN, H/CTS-BEN and CTSBEN NCs, respectively. Kinetics studies fitted well with the pseudo-second order model with rate constants of 25.64, 28.65 and 25.00 mg/g by H/CTS-BEN, Arg/CTS-BEN and CTS-BEN NCs, respectively. The adsorption of the COD is well described by Langmuir equations (R2 0.99). Results show that the synthesized NCs is promising and efficient in purifying landfill leachate.

THE EFFECTIVENESS OF COMBINED DUCKWEED (Lemna minor), CYANOBACTERIA IN THE DEGRADATION FOR CADMIUM (Cd) AND IRON (Fe) METALS

The high content of cadmium (Cd) and iron (Fe) is one of the causes of environmental and health problems. This study aims to test the combined effectiveness of duckweed (Lemna minor) and Cyanobacteria in the degradation of heavy metals cadmium (Cd) and iron (Fe) in leachate water at the Gampong Jawa landfill. This effectiveness test was carried out with a variation of contact times of 2, 4, and 6 days and the test was carried out using an Atomic Absorption Spectrophotometer (AAS). Physical changes occurred in the water, and Cyanobacteria became blackened and duckweed (Lemna minor) was pale in color. The highest decrease in heavy metal cadmium (Cd) occurred on day 4 with a percentage of 94.55% and in iron (Fe) occurred on day 2 with a percentage of 62.58%. This demonstrates the effectiveness of incorporating duckweed (Lemna minor) and Anabaena in reducing heavy metals like cadmium (Cd) and iron (Fe) in leachate water.

Antibacterial Effectiveness Test of Lemongrass Leaf (Cymbopogon Citratus) Boiled Water In Decreasing The Number of Escherichia Coli Bacterial Colonies

The presence of disease can be caused by a microorganism (virus, bacteria, fungus and parasite), and the environment that can infect a person either directly or through intermediaries. Environmental components such as air, water, food, and others are the natural transfer paths of disease. So that humans must maintain personal hygiene, the environment and equipment that is often used such as cutlery to avoid the threat of pathogenic microorganisms. Contamination in the washing process of cutlery by water containing Escherichia coli bacteria will damage the quality of food and cause diarrhea. One of the efforts to reduce the number of germs is to disinfect using chemicals such as chlorine. However, the use of chemicals actually has a negative impact on health and the environment, we need alternatives that do not cause pollution and are safe for humans such as the use of natural materials. One of them is lemon grass which can be used as an antibacterial.
 
 This experimental study aimed to determine the antibacterial effectiveness of lemongrass leaves with concentrations of 10%, 15%, 20% and 25% in reducing the number of Escherichia coli bacterial colonies after 5 minutes, 10 minutes and 15 minutes of contact, using the spread plate method with EMBA media. The results showed a decrease in the number of Escherichia coli bacterial colonies after treatment using boiled water from lemongrass leaves from a concentration of 10% after 5 minutes of contact. Based on the ANOVA analysis, it was found that p-value 0.05 there was a significant difference in each variation of concentration and contact time. The boiled water of lemongrass leaves with the highest level of effectiveness is in concentration of 25% with a contact time of 15 minutes.

Utilization of Papaya Seed Powder as a Bioadsorben to Reduce Total Iron (Fe) in Wastewater

Papaya is a tropical plant that is widely cultivated in Indonesia. Papaya seeds have a high cellulose content, so that papaya seeds can be used as raw material for adsorbents (biosorbents). Biosorbent is used to reduce environmental pollution through the absorption of various types of liquid waste including heavy metals. Fe is an essential heavy metal if in excess amounts can cause toxic effects. One of the methodes to reduce of iron ion in wastewater is the adsorption method is using papaya seed biosorbents. The aim of study was to determine the effectivness of using papaya seedd as bioadsorbent to reduce of iron ion in the wastewater. Papaya seed as the adsorbent agent activated ones was used in five particle size and contact time variations in order to determine the optimum particle size and contact time of papaya seed powder to absorb the heavy metals. The results show that the optimum adsorbent particle size was 100 mesh and the optimum contact time was 60 minute. The adsorption efficiency of (Fe) metal ions in wastewater was 60%, the adsorption capacity value was 0.365 mg/g. Kinetic modelling of adsorption process is pseudo second order.

Pengaruh Variasi Waktu Kontak dan Dosis Adsorben Fly ash teraktivasi NaOH terhadap Adsorpsi Metilen Biru

A rapid growth of textile industry creates a new problems on environment, one of those is the presence of dye waste. Methylene blue is one of the dyes which is toxic to living things, one of those triggers cyanosis for human and bother photosyntesis of algae. Therefore, it needs the effort to reduce, one of those is by adsorption. This study aims to determined the effect of dosage adsorbent variation and contact time variation to adsorb methylene blue. Adsorption is an adsorbate molecule absorption process that occurs on the surface of the adsorbent. This study used fly ash from PG. Pagottan and has been activated by NaOH. Measure method of this study using UV-Vis Spectrophotometry to measure concentration of methylene blue at maximum wavelenght. Based on data, NaOH-activated fly ash and non-activated fly ash following Langmuir isotherm adsorption, it mean a monolayer site is formed. Adsorption capacity also increase after activation, it about 21,74 mg/g to 23, 25 mg/g. Based on the study fly ash has a potential as a new adsorbent.

Uji Kemampuan Adsorpsi Komposit Keratin Bulu Itik-Polietilena Terhadap Ion Besi(III)

Research on the adsorption of iron(III) ion using an adsorbent from duck feather-polyethylene composite has been studied. This study aimed to determine the optimum pH conditions and the optimum contact time required in the iron(III) ion adsorption process. Optimum pH and contact time are then measured using AAS to determine the amount of iron(III) ion adsorbed with the duck feather-polyethylene composite adsorbent. The determination of the optimum pH was carried out with pH variations which are 2, 3, 4, 5, 6, 7, and 8, while determination of the optimum contact time was carried out with contact time variations which are 40, 60, 80, 100, 120, 140, and 160 minutes. The result of this research showed that optimum conditions for iron(III) ion adsorption at pH 6 and contact time at 80 minutes, which each adsorption capacity are 68.33% and 79.78%.

Reduction of TSS, COD, Oil and Fat in Palm Oil Mill Waste Using Dissolved Air Flotation Method

This study aims to determine the effect of variations in pressure and contact time of wastewater with air to decrease the parameters of TSS, COD, and oils and fats contained in palm oil wastewater. This study uses a series of Dissolved Air Flotation (DAF) process units with the addition of Poly Aluminum Chloride (PAC) coagulant. This research begins with the manufacture of a series of DAF tanks and flotation tanks. Waste flow is carried out in batches and the air is flowed upflow through the bottom hole of the DAF tank. The pressure variables used in decreasing the parameters of TSS, COD, and oil and fat are absolute 2; absolute 2.5; and absolute 3 atm. The contact time variables for decreasing TSS, COD, and oil and fat parameters were 15, 30, 45, 60, and 75 minutes. The results showed a decrease in each of the tested parameters. The effective pressure to reduce the value of the TSS parameter is the absolute pressure of 3 atm and the absolute pressure of oil and grease is 2.5 atm. While the effective pressure to reduce the value of the COD parameter is an absolute pressure of 3 atm. The best contact time between air and wastewater to set aside the values of the TSS, COD, and oil-fat parameters was 75 minutes.

Optimum conditions for absorption of copper (Cu) from its solution using durian skin waste biomass (Duriobzibethinus)

This study aimed to determine the optimum conditions for durian skin biomass to absorb copper metal (Cu) from its solution. Determination of optimum conditions includes optimum weight, optimum pH for biosorption, biosorption contact time, and initial concentration of copper metal (Cu). Determination of the adsorbed analyte used Atomic Absorption Spectrophotometry (AAS). In this study, the durian skin used was obtained from local durian skin waste from the Parigi Regency, Central Sulawesi Province. The parameters tested were the weight of the adsorbent or the weight of the powder with variations of 50 mg, 70 mg, 90 mg, 110 mg, and 120 mg, variations in contact time 20 minutes, 40 minutes, 60 minutes, 80 minutes, and 110 minutes, variations in pH 2, 3, 4, 5, 6 and concentration variations of 50 ppm, 100 ppm, 150 ppm, 200 ppm, and 250 ppm to determine the optimum conditions for adsorption of copper (Cu). The results of this study indicate that the optimum conditions for absorption of copper metal by durian skin biomass respectively, the optimum weight for biosorption was 120 mg with an absorption capacity of 99.08%, the optimum contact time was 100 minutes with an absorption capacity of 98.31%, the optimum pH was 5 with the absorption capacity of 99.72% and the optimum concentration of 50 ppm with an absorption capacity of 98.92%.

Aplikasi Melati Air Dalam Menurunkan BOD dan COD Limbah Cair Kelapa Sawit

Wastewater produced oil industry mustard t containing organic content of high BOD and COD. BOD and COD stating the amount of dissolved oxygen needed by microorganisms to decompose the material organic of a waste. Therefore, high levels of BOD and COD must be lowered in organic levels before being discharged into the water. One way that can be done using phytoremediation technology that is environmentally friendly. The purpose of this research to see the effectiveness of the water jasmine plant's ability to reduce levels of BOD and COD in palm oil industrial wastewater. This study used a batch system with variations in the number of plants used were 4, 12 and 16 individual plants and variations in contact time of 5 and 9 days. The initial testing of the waste obtained a BOD value of 4,236 mg / L, and a COD value of 5760 mg / l. After the phytoremediation test was carried out, the best decrease in BOD values was up to 96 mg / L and the greatest efficiency was obtained 97.73%. The decrease also occurred very well in COD, namely up to 342 mg / L with the greatest efficiency obtained by 93.88%. The decrease in the optimum levels of BOD and COD was found in variations in the number of plants 16 and on the 9th day. This proves that these plants are effective in eliminating liquid waste levels in the palm oil industry, especially BOD and COD

Fruit peel-based mesoporous activated carbon via microwave assisted K2CO3 activation: Box Behnken design and desirability function for methylene blue dye adsorption

A low-cost fruit waste namely watermelon peel (WMP) was utilized as a promising precursor for the preparation of mesoporous activated carbon (WMP-AC) via microwave assisted-K2CO3 activation. The WMP-AC was applied as an adsorbent for methylene blue dye (MB) removal. Several types of characterizations, such as specific surface area (BET), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), Elemental Analysis (CHNS/O), and Fourier Transform Infrared Spectroscopy (FTIR) were used to identify the physicochemical properties of WMP-AC. Furthermore, Box-Behnken design (BBD) was applied to optimize the influence of the adsorption operational variables (contact time, adsorbent dose, working temperature, and solution pH) on MB dye adsorption. Thus, based on significant interactions, the optimum BBD output shows the best removal of 50 mg·L−1 MB (92%) was recorded at an adsorbent dose of 0.056 g, contact time of 4.4 min, working temperature of 39 °C, and solution pH 8.4. The Langmuir uptake capacity of WMP-AC was found to be 312.8 mg·g−1, with the best fitness to the pseudo-second-order kinetics model and an endothermic adsorption process. The adsorption mechanisms of MB by WMP-AC can be assigned to the hydrogen bonding, electrostatic attraction, and π–π stacking. The findings of this study indicate that WMP is a promising precursor for producing porous activated carbon for MB dye removal.

Synthesis of Oil Palm Fronds Charcoal as Adsorbent to Reduce Levels of Fe (III) in Peat Water

The high content of carbon compounds in palm fronds (OPF) makes them potentially useful as an adsorbent. The carbonization method was used for the adsorbent synthesis process. This process began with collecting palm frond waste and then drying and sifting the adsorbent particle. This process resulted in the escape particles with a size of 80 mesh and suspended particles with 120 mesh. Then this process continued by carbonizing the palm fronds with temperature variations starting from (400, 500, and 600°C) for 60 minutes to obtain Charcoal Oil Palm Fronts (COPF). The obtained COPF was determined for moisture and ash content and characterized using FTIR, XRD, and SEM to determine the surface, functional groups, degree of amorphism, crystallinity, and surface morphology. The adsorption efficiency of COPF was applied to the adsorption of Fe (III) in peat water under varying contact time, adsorbent mass, and peat water volume conditions. The water and ash content of COPF qualify the technical quality requirements for activated charcoal according to SNI 06-3730-1995. FTIR analysis detected the presence of vibrations of the C-O, O-H, C=O, C-C, and C-H functional groups on the COPF surface. The XRD pattern showed the existence of a semi-crystalline (002) and (100) plane structure, which is shown at scattering angles of 2θ = 22o and 42o. The surface morphology of COPF showed that as the carbonization temperature increased, the number of pores formed increased, and the pore size decreased. The best adsorption test results were obtained with a contact time of 30 minutes, an adsorbent mass of 1.00 g, and a peat water volume of 100 mL. The highest Fe adsorption efficiency was achieved by COPF 500, where the adsorbed mass was 0.054 mg. Increasing the carbonization temperature causes the water content to decrease and the ash content to increase. High water content and ash content cause a decrease in adsorption efficiency because they can cover the pores of the adsorbent.

Fabrication of Novel Nanohybrid Material for the Removal of Azo Dyes from Wastewater

This study attempted to harness the dual benefit of adsorption and photocatalytic degradation for efficiently removing a model anionic azo dye, Orange G, from an aqueous solution. For this purpose, a series of bifunctional nanohybrids containing different proportions of naturally occurring biopolymer chitosan and ternary photocatalyst made of kaolinite, TiO2, and ZnO were prepared through the dissolution of chitosan in acid and subsequent deposition on ternary photocatalyst. The characterization through Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectrum (EDS) have confirmed the successful fabrication of nanohybrids from TiO2 and chitosan. The adsorptive separation of Orange G from the aqueous solution and subsequent degradation under solar irradiation was thoroughly studied by recording the λmax value of dye in the ultraviolet–visible (UV-Vis) spectrophotometer at various operating conditions of pH, dye concentration, contact time, and compositional variation. The nanohybrid (TP0.75CS0.25) fabricated from 75% ternary photocatalyst (w/w) and 25% chitosan (w/w) removed 97.4% Orange G within 110 min at pH 2.5 and 10 mg/L dye concentration. The relative contribution of chitosan and ternary composite on dye removal was understood by comparing the experimental results in the dark and sunlight. Recyclability experiments showed the suitability of the nanohybrid for long-term repeated applications. Equilibrium experimental data showed a better correlation with the Langmuir isotherm and pseudo-second-order kinetic model. The rapid and nearly complete removal capacity, long-term reusability, and simple fabrication technique make this novel nanohybrid a promising advanced material for removing hazardous azo dyes from industrial effluents.

Biosorption of Chromium (II) Ion from Textile Effluent Using Watermelon Shell-Activated Carbon

Watermelon Shell, an agricultural waste, was employed for the adsorptive removal of chromium (II) ion Cr 2+ from textile effluent. This study analysed the adsorbent's active sites and morphological structures using FT-IR, SEM, XRD, and XRF. The independent variables' effect, contact time, adsorbent dosage, and pH were predicted using Response Surface Methodology (RSM) for chromium adsorption onto Watermelon Shell Activated Carbon (WSAC). The experimental results indicated that NaOH activation effectively improved WSAC's adsorption capacity. The maximum adsorption capacity was 54.53 %, with an adsorbent dosage of 0.6 g/l, pH of 6.0, and agitation time of 40 min. The high correlation coefficient (R 2 =0.978) between the model and the experimental data showed that the model predicted the removal of Cr 2+ from textile effluent using Watermelon Shell Activated Carbon efficiently.

Pengaruh Waktu Kontak dan Bobot Biomassa Kangkung Air (Ipomoea aquatica) Terhadap Penurunan Kadar Total Suspended Solid (TSS) Air Limbah Rumah Sakit dengan Metode Fitoremediasi

Hospital waste water is one of the causes of environmental pollution. Where river pollution is one of the effects (Sari et al., 2020). The high content of Total Suspended Solid (TSS) is the one of the parameters of river pollution. High TSS content in rivers has the potential to cause siltation (Ruhmawati et al., 2017). So that the management of hospital waste water is very important (Sari et al., 2020). One of the economical waste treatment methods is the phytoremediation (Novita et al., 2019). The research was conducted by mixing wastewater with acclimatized water (1:1), then 4 liters were taken and put into a container containing water spinach with a weight of (50, 100, 150, 200, 250) grams. Tests were carried out with variations in contact time (1, 2, 3, 4, 5) days. Samples were taken as much as 500 ml and then tested for its TSS content. It was concluded that contact time had an effect on decreasing TSS levels, while for biomass weight it had no effect. In addition, it was found that the effectiveness of water spinach in reducing the highest TSS level was 85% with a TSS level of 3 mg/L which occurred on a weight variation of 250 grams on the second day and at a weight of 100 and 200 grams on the third day, which means that water spinach was quite effective in reducing TSS levels in hospital wastewater.

Synthesis Of Spherical Chitosan-Zeolite Composite (Ch-Z Spherical) From Shrimp Shells Using Crosslinking Method As Adsorbent Of Metal Ca (Ii) And Mg (Ii)

Water quality is very important to know because it is related to the use of water for daily needs and has a direct effect on the health of humans who consume the water. Water quality includes three main parameters, namely physics, chemistry, and biology. One of Chemical water quality parameter is the level of water hardness. One of the efforts made to reduce hardness is to add materials that can bind Ca (II) and Mg (II) metal ions. In this study, the material used was chitosan from shrimp shell waste modified with zeolite into a chitosan/zeolite composite in a spherical form using Tripolyphosphate as a crosslinking which interacts to form bonds through ionic gelation. The spherical chitosan-zeolite composite was characterized using FT-IR. The results of characterization using FT-IR at a wavelength of 4000-450 cm-1 show a typical IR spectrum for Chitosan-Zeolite Spherical (Ch-Z Spherical) at wavelengths 1639 cm-1, 1638.71 cm-1, respectively. and 1638.58 cm-1 which is the -C⁼N strain or structural change (deformation) of NH2.Chitosan-Zeolite Spherical Composite was applied to reduce the concentration of Ca(II) and Mg(II) metals which can cause water hardness. To determine the effectiveness of the optimum absorption time of the Spherical Chitosan-Zeolite composite, contact time variations were made, namely 15, 30, 45, 60, 90 with a concentration of 500 ppm of Ca (II) and Mg (II) metals with a stirring process. The results showed that the optimum time for the absorption of metal Ca(II) was 90 minutes with an absorption concentration of 0.012 mol/g. The optimum contact time of the spherical chitosan-zeolite composite to Mg(II) metal ion is 15 minutes with an absorption concentration of 0.1 mol/g.

Characteristics of three lower limb joint kinetics affecting rebound jump performance.

The stretch-shortening cycle (SSC) motor execution ability of the lower limb was measured using the rebound jump index (RJ-index) in RJ test; this performance is influenced by the interaction of the forces exerted by the three joints of the lower limb.We aimed to determine RJ performance variables and identify the lower limb kinetic variables that affect them. One hundred two female university students (age, 20.1±1.0 years; height, 164.6±7.2 cm; mass, 58.9±7.3 kg) for whom RJ performance variables (RJ-index, jump height, and contact time) and joint kinetics (torque, power, and work) were measured. Statistical analysis showed a strong correlation between the RJ-index and jump height or contact time (r = 0.920, -0.726, p < 0.05) but a weak correlation between the jump height and contact time (r = -0.384, p < 0.05). Furthermore, positive ankle power was the most influential factor for RJ performance variables; additionally, positive knee power and hip work and eccentric knee torque significantly influenced jump height, and positive ankle power, negative work and power, and concentric torque significantly influenced the contact time. The acquisition of the jump height and a shorter contact time requires different kinetic variables. Furthermore, the characteristics of the force exerted by the three joints of the lower limb that compose the RJ-index may be different even if the RJ-index has the same value. Therefore, by assessing not only the RJ-index but also the jump height, contact time, and characteristics of lower limb joint kinetics in the RJ test, it is possible to conduct effective training to improve lower limb SSC motor execution performance according to individual characteristics.

AKTIVASI ZEOLIT ALAM SEBAGAI ADSORBEN PEWARNA ALAMI KULIT BUAH NAGA (PITAYA)

Natural zeolite is one of the alternative adsorbents with good absorption capabilities, including in absorbing color. The adsorption ability of zeolite can be increased by the activation process because it can increase the Si/Al ratio and pore size. Dragon fruit peel is a natural material that can be used as a natural dye because it contains betacyanin pigments which are equivalent to synthetic dyes. This study aimed to investigate the characteristics of activated green and brown zeolite and their adsorption ability on natural dyes of dragon fruit peel. Zeolite was activated chemically using 3M HCl solution and physically through a heating process of 500°C, then characterized using XRD and FTIR. The zeolite adsorption process was carried out with variations in contact time of 30, 60 and 90 minutes and variations in the mass of the adsorbent 0.1, 0.3 and 0.5 grams. The results of XRD analysis showed that the green and brown zeolite contained mordenite, nepheline and quartz minerals. The highest percentage of color degradation in the adsorption process was in brown zeolite at 27.70% at a contact time of 90 minutes and 88.2% at an adsorbent mass of 0.5 grams. Differences in brown zeolite before and after adsorption can be seen from the shift in the wavelength of each functional group due to the interaction with dragon fruit peel.

Decrease in Calcium Oxalate Levels in Porang Bulbs With Variations in Contact Time, Temperature and Volume of Averrhoa bilimbi Juice Solution

Porang tubers contain glucomannan which is widely used in industry. The high calcium oxalate contained in porang tubers is an obstacle in the use of porang tubers in the food industry. Organic acids such as citric acid can reduce calcium oxalate levels in porang tubers. Porang tubers cut with a thickness of 0.5 cm were immersed in a 7% solution of star fruit juice with variations in soaking time, temperature and volume of the soaking solution. Soaking porang tubers in 250 mL of star fruit juice solution at 60 °C for 15 minutes gave better results than soaking porang tubers at room temperature for 60 minutes. The lowest level of calcium oxalate was found in porang tubers that had been soaked in 7% starfruit solution for 15 minutes at 60 °C, which was 1.0873% (w/w).