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Coagulation is a water and wastewater treatment technology that has been widely used due to its high efficiency and effectiveness. Various inorganic salts are commonly used as coagulant; however, there are some negative impacts of utilization of these chemical coagulants, such as high costs, large sludge volume, and also potential negative impact to human health. To overcome these problems, natural-based coagulants have been explored to reduce and substitute chemical coagulants. In this study we investigated utilization of Leucaena leucocephala seed protein, extracted using 0.5 M MgCl2 solution as natural coagulant to treat synthetic Congo red wastewater. From the protein solubility profile at various pH, it could be observed that leucaena protein’s isoelectric point was around pH 4. The optimization of coagulation condition was done by using Response Surface Method (RSM)—Central Composite Design (CCD) with variations of pH (2.93–4.12), coagulant dose (183.52–496.58 mg eq BSA/L), and dye concentration (44.1–56 mg/L). This experimental design was used to obtain the optimum condition that gave maximum dye removal percentage and minimum sludge volume. It was found that pH, coagulant dose, and dye concentration were significant for dye removal and sludge volume. Furthermore, it became evident that charge neutralization was the coagulation mechanism in this study. Based on the obtained model, 88.61% dye removal with 16.93 mL/L sludge volume was obtained at the optimum condition. The predicted optimum condition was in a good agreement with experimental data with relatively low error value. The obtained result implies good potency of leucaena as natural coagulant.

This study focused on utilization of Leucaena leucocephala seeds’ extract and iron oxide nanoparticles (IONPs) under magnetic field to provide effective coagulation process. Leucaena seeds’ extract was obtained using 3 M NaCl solution as solvent at feed-to-solvent mass ratio of 1:20. IONPs were synthesized using co-precipitation method. The obtained IONPs were analyzed using scanning electron microscopy, X-ray diffraction and transmission electron microscopy. Based on analysis results, the obtained IONPs were the agglomerate of Fe3O4 phase with average particle diameter of 14.6 nm. The extract and IONPs were used as natural coagulant at various pHs (3–12), coagulant dosages (4–40 mL extract/L), and IONPs concentrations (0.5–3 mg/mL extract) under external magnetic field. It was obtained that pH 3 was the best pH because positively charged Leucaena protein at pH 3 acts to neutralize negatively charged Congo red molecules. The highest removal was obtained at coagulant dosage of 20 mL/L, and further increase in dosage was decreasing the removal due to colloid re-stabilization effect. The variation of IONPs concentration did not give any effect on the %removal and sludge volume. However, further investigation using pseudo-second-order kinetic model showed that the increase in IONPs concentration gave increase to the kinetic constant, signifying faster settling kinetics. The best condition was obtained at pH 3, coagulant dosage 20 mL/L, and IONPs concentration of 3 mg/mL extract that gave 90% Congo red removal, 30 mL/L sludge volume, and 30 min settling time.

Activated carbon (AC) has been utilized for various applications including as an electrode for supercapacitor, i.e., electric double-layer capacitor (EDLC) as well as hybrid capacitor such as lithium ion capacitor. In this research, salacca peel was used as a raw material for AC. It was chosen among other biomass wastes because it is abundant and is still considered as a waste. The hydrothermal carbonization was conducted at 5 MPa, temperature of 200–250 °C, and 5 h in subcritical water, which is a green dehydrating agent. The effect of parameters (temperature and addition of citric acid as a catalyst) on the hydrochar and AC product was investigated. The hydrochar from hydrothermal carbonization was activated by chemical activation using potassium hydroxide (KOH) as an activated agent to enhance the surface area and porosity. The morphology of both hydrochar and AC was measured by scanning electron microscopy (SEM), its chemical transformation was measured by Fourier transform infrared spectroscopy (FTIR) while the surface area and pore size distribution were measured by nitrogen adsorption at 77.35 K. The electrochemical performance of activated carbon from salacca peel as well as commercial activated carbon using a coin cell in a Li half-cell system was evaluated by CV, GCD, and EIS. The results show that the presence of citric acid contributes to higher specific capacitance in the rate performance test of LIC at different current density as well as in long rate stability test.

Hard carbons are one of the most promising carbon anode materials for sodium ion batteries (SIBs) due to the high specific capacity and excellent cycle properties. Among the precursors used to synthesize hard carbon, natural starches are of great interest due to their unique morphologies. In this paper, ganyong starch based hard carbons (GSHC) were prepared by direct carbonization at various temperatures (700–1100) °C. The obtained hard carbons exhibit high reversible capacities of sodium-ion batteries of about 239 mAh g–1 at current density of 0.1 C. after 100 cycles. The excellent cycle profiles are attributed to the unique morphology and defect carbon structures.

In this study we compared utilization of FeCl3 extracted leucaena protein and FeCl3 to treat synthetic Congo red wastewater. The extraction was done at leucaena seeds kernel to 0.5 M FeCl3 solution ratio 1:20 with various initial extraction pH (2 to 9). It was observed that pH 2 gave the highest protein concentration of 1.7 mg eq BSA/mL, compared to other pH. The extract obtained at this condition was further used in the coagulation study. At various initial coagulation pH (2 to 10), the highest Congo red removal was observed at initial coagulation pH 6. This result indicated that FeCl3 was the active coagulating agent despite of the presence of leucaena extract, with charge neutralization coagulation mechanism. Variation of coagulant dosage was done from 4 to 44 mL/L. At dosage 4 to 12 mL/L, low color removal was observed due to insufficient coagulant to neutralize Congo red molecules. Over addition of coagulant also lowered the coagulation efficient, and increased the sludge volume due to colloid re-stabilization phenomenon. The best Congo red removal was observed at coagulant dosage 20mL/L FeCl3 – leucaena extract combination with color removal of 95% with 9 mL/L sludge volume, slightly higher compared to FeCl3 only. Based on this result, it could be concluded that FeCl3 could act effectively as coagulant without the presence of leucaena extract.

Natural coagulants from plants resources have gained a lot of attention as it is renewable, biodegradable, non-hazardous, lower cost, and less sludge generated compared to chemical coagulants. However there are still some drawbacks, namely long settling time and possible increase of dissolved organic carbon in the treated water. In this paper we tried to address these drawbacks by utilizing citrate modified Fe3O4 to adsorb protein from Leucaena leucocephala as the active coagulating agent. The effect of trisodium citrate concentration and protein adsorption pH to the adsorbed protein was investigated. It was found that the trisodium citrate concentration of 0.5 M and pH 4.0 gave the highest protein adsorption. The obtained magnetic coagulant was furthermore characterized using Scanning Electron Microscopy, X-ray Diffraction, Fourier Transform Infrared Spectroscopy, and Transmission Electron Microscopy to observe the characteristics before and after protein adsorption. Furthermore, the effect of pH (2 to 10) and coagulant dosage (60 to 600 mg L-1) to the removal of synthetic Congo red wastewater and sludge volume formation was investigated. It was found that pH 3 was the best pH for coagulation due to charge neutralization mechanism of leucaena protein. Furthermore the highest removal was obtained at dosage 420 mg L-1 with 80% removal. This result was comparable with crude extract of leucaena with half settling time (20 min) and lower increase of permanganate value, indicating lower increase of dissolved organics in the treated water.

The simultaneous oxidation of cyanide and reduction of cadmium from electroplating wastewater using UV/TiO2 photocatalysis was investigated in this study. The investigation was performed using a batch-wise 3 L bubble-column photoreactor equipped with a 64-Watt low-pressure ultraviolet (UV) amalgam lamp (20 W at 254 nm). Preliminary experiments were conducted to identify the optimum aeration rate for ensuring the mixing of the catalyst and the wastewater. More specifically, this study focused on the two main factors that influence the effectiveness of oxidative and reductive processes, namely the TiO2 concentration (0.5–2 g/L) and the solution’s pH (11–13), at cyanide and cadmium ion concentrations of 50 and 100 ppm, respectively. A sample was taken every 30 minutes for 3 hours, and the cyanide and cadmium ion concentrations were determined using an ion-selective electrode and atomic absorption spectroscopy (AAS), respectively. It was determined that 3 L/min aeration was optimum, resulting in the removal of approximately 80% of the pollutants. A further increase in the aeration rate resulted in a decrease in the %removal rate due to competition between the oxygen and cadmium ions in terms of reacting with the electrons produced by the photocatalyst. An increase in the pH resulted in an increase in both the removal rate and the kinetics due to the high availability of the hydroxide ions needed to form the radical hydroxide that effectively oxidized the cyanide ions. It was observed that an increase in the TiO2 concentration increased both the removal rate and the kinetics until the optimum point, after which the performance of the photocatalyst decreased due to the shielding effect of the UV resulting from the excessive level of TiO2 present in the mixture. Within the experimental range, the best (most effective) condition was chosen based on the pseudo first-order rate constants. The best condition for cyanide oxidation was identified at pH 13 and 1 g/L TiO2 with kCN- 0.033 min-1, while the reduction of cadmium was found to be optimum at pH 13 and 2 g/L TiO2 with kCd2+ 0.039 min-1.

Indonesia is a tropical country which is known for its high variety of natural resources. However, there is limited access to clean water, thus forcing people in rural areas to use turbid water. Furthermore, some of water sources in Indonesia are already polluted by heavy metals with high biological oxygen demand (BOD) and chemical oxygen demand (COD) value. Simple and easy water purification methods are needed to overcome this situation. Coagulation and flocculation are widely used method to treat water. However, chemical coagulants (alum, ferrum, PAC, etc.) are not easily obtained and could cause some health problems if treated water is consumed. Natural coagulants have a good potential to solve these problems. Various possible plant-based natural coagulants which are abundant in Indonesia are highlighted in this paper. Fruit wastes and inedible legumes are suggested to be used as natural coagulant as there are no food competition presents. Further research is needed especially to scale up laboratory scale research that has been done in these years; thus, it can be applied to solve clean water scarcity problem.

This study describes preliminary study of tamarind seeds kernel powder as natural coagulant for color removal of drimarene dark red (DDR) synthetic wastewater (20 mg/L). The effect pH (2-7), dosage (1-3 g/L), and their interactions were investigated using general factorial design. The seeds powder was also characterized using Fourier Transform Infrared Spectroscopy (FTIR) to observe the possible active coagulating agent in this study. It was found that the seeds powder contained protein that could act as coagulant. Dosage, pH, and their interactions were found to be statistically significant to the removal of DDR. Highest removal of 84.60% was obtained at pH 3 and dosage 3 g/L.

Coagulation is a well-known technology applied in water and wastewater treatment. Inorganic salts, such as alum, ferrous sulfate, and polyaluminum chloride, are usually used. It is widely known that utilization of these inorganic coagulants poses several disadvantages, such as high coagulant cost and high sludge volume that increase water treatment expenses. The use of alum also poses health risk to human as it may cause degenerative diseases. In order to minimize these disadvantages, the use of various coagulants from natural resources has been recently proposed. In this research, study was performed on the extraction and use of a potential natural coagulant (Leucaena leucocephala) seed kernel as natural coagulant. Leucaena seed kernel was extracted at various NaCl concentrations (0–5 mol L−1). Extract with highest protein content obtained at NaCl concentration of 3 mol L−1 was further used to treat a synthetic wastewater model substance (Congo red solution) at various pH (2–10) and dosage (2–40 mL L−1). This natural coagulant successfully removed 99.9% of the color at pH 3 and dosage 10 mL L−1, with only half sludge volume discharged when compared to alum. The result suggests that leucaena is a promising natural coagulant for water and wastewater treatment.

Based on the chemical similarity, large abundance and cheap price, sodium ion battery (SIB) can become a promising alternative to subsitute lithium ion battery (LIB). The main issue of the development of SIB is to look for a suitable anode material since graphite, the anodes in LIB, can not be used in SIB because of the unstable thermodynamic properties . In this work, we report the synthesis of hard carbon anodes for SIB from sagoe starch that are prepared by hydrothermal carbonization followed by the pyrolysis process at moderate temperature between 500 °C and 900 °C. Morphology studies show that the hard carbon is very porous porous with interconnected porous network. X-ray diffraction and Raman spectroscopic analysis show that the carbon materials have disordered carbon structure with large interlayer spacing pf 0.39 nm. The electrochemical characterizations reveal that hard carbon which is prepared at 700 °C (STHC-700) shows the best performance, showing 375 mAh g−1 and 290 mAh g−1, initial discharge and charge capacities, respectively. Specific capacities of about 268 mAh g−1 and 178 mAh g−1 are obtained for WHC-700 material at a current density of 50 and 200 mA g−1, respectively. The sagoe starch produce hard carbon material at moderate pyrolysis temperature with microstructural properties and large interlayer spacing. These properties are contributing for the excellent electrochemical performance as anodes for sodium ion batteries.

Carbon Nanospheres (CNSs) have been synthesized by thermal pyrolysis method. A mixture of Fe-catalyst supported activated carbons and palm oil was used in the furnace to produce CNSs. Prior to the synthesis of CNSs, Fe-catalyst was deposited onto the surface of activated carbons by wet incipient impregnation method. The ratio of carbon support and palm oil was varied (1:1, 1: 2 and 1:3) to obtain CNSs. The characteristics of produced CNSs were then evaluated with BET surface area analysis, pore size distribution analysis, scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). It was found that some impurities were still found in the CNSs in the forms of iron oxide and amorphous carbons.

Since its discovery, carbon nanomaterials, such as nanotubes, nanohorns, nanoribbons and so forth, have gained a lot of attention among researcher. Carbon nanospheres (CNSs) are one of novel carbon nanostructures which are known for its potential application in many fields, such as electrodes in supercapacitors and lithium ion batteries, adsorbents, and catalyst support. In this study, Carbon Nanospheres (CNSs) was synthesized using simple pyrolysis process under nitrogen atmosphere. Cooking palm oil was used as natural and renewable carbon precursors, ferrocene as catalyst and activated carbon as support. Ferrocene was used at various concentrations (2.5, 5.0, and 7.5 g/100 mL precursor). The effect of catalyst amount to the morphology and characteristics of CNSs obtained was observed by x-ray diffraction (XRD), BET surface area analysis, scanning electron microscope (SEM), and energy dispersive x-ray spectroscopy (EDS). Peak of C (002) and (100) was observed in XRD spectra of all catalyst concentrations, while there was decrease of surface area in all samples, indicating the covering of activated carbon pores by Fe catalyst and CNSs. With increase of the catalyst concentration, there was also increase in content of Fe and O. The most dense CNSs structure was obtained by pyrolyzing palm oil onto activated carbon support with ferrocene concentration 7.5 g/100 mL, with average diameter of 87.5 nm.

Textile wastewater contains a lot of pollutants which is hazardous if directly discharged. Coagulation and flocculation using inorganic salts were widely used to treat textile wastewater. However this method pose some drawbacks, such as high coagulant cost, large volume of sludge was produced, and potential health problems if the water is consumed. In this study we explore utilization of natural coagulant as an alternative to inorganic salts to treat textile wastewater. This study describes utilization of papaya seeds powder as a natural coagulant for synthetic textile wastewater of drimarene dark red (DDR) with initial concentration of 10 mg/L. The effect of coagulant dosage and pH to the %removal of colour in wastewater was studied using central composite design. The potential active functional groups in papaya seeds powder was characterized using Fourier Transform Infrared Spectroscopy (FTIR). It was found that papaya seeds powder contained –OH, -NH, C=O functional groups that indicate good potential as natural coagulant. The cubic model obtained was in good fit with experimental data, which was shown in R-squared value of 0.995. It was found that coagulant dosage, pH, and its interaction were significant to the removal of synthetic dye in wastewater. The decrease of pH gave higher %removal due to protonation of papaya seeds powder active coagulating agent resulting on better electrostatic interaction with dyes. The increase of dosage also gave increase in %removal until its optimum condition. After optimum condition, the %removal decreased due to colloid re-stabilization. The optimum condition was obtained at dosage of 0.57g/L and pH 1.97 with 84.77% of predicted colour removal and this result was in agreement with experimental response value.

In this study the effect of activated carbon support modification to synthesis of CNSs was observed. Modification of activated carbon was done by using nitric acid. The effect of modification was analyzed from its FTIR spectra. The Fe catalysts were deposited on to the support by using urea deposition precipitation method at various initial catalysts concentration. CNSs was synthesized by utilizing cooking palm oil as renewable carbon source, and pyrolized at 700°C for 1 hour under nitrogen atmosphere. The products obtained then analyzed using SEM-EDS, TEM, XRD, and Raman spectroscopy. The modification of activated carbon support had increased the oxygen functional group. This increase resulted on increase of metal catalysts deposited on activated carbon surface. Peak of C (100) was observed, while ID/IG of samples were obtained around 0.9, which is commonly obtained for CNSs. High catalysts loading on modified activated carbon support caused decomposition of CNSs and formation carbon onion.