Synthesis of Activated Carbon from Rice Husk as A Filter For Iron (Fe) And Copper (Cu) In Well Water

This study focuses on the synthesis of activated carbon through the calcination method, designed as an absorber for iron (Fe) and copper (Cu) metals in well water previously investigated. The raw material utilized for activated carbon production is rice husk waste, with variations in calcination temperatures set at 700°C, 800°C, and 900°C. The characterization of the activated carbon involved XRD testing for phase analysis, SEM-EDX analysis on rice husk to discern the morphology and composition of the activated carbon components, and absorption performance analysis using AAS. The XRD testing results revealed an amorphous shape in samples calcinated at 700°C and 800°C. However, the 900°C samples exhibited the formation of the tridymite phase. SEM-EDX results showcased an increased surface area and a more compact pore structure, attributed to high-temperature calcination. AAS testing results indicated an improvement in the absorption capacity of iron (Fe) and copper (Cu) metals. In this research, each 4 g activated carbon sample proved most effective at reducing the initial iron (Fe) metal content from 8.06 mg/L to <0.009 mg/L, achieving an impressive 99.88% absorption. Furthermore, with every 2 g sample, copper (Cu) metal was efficiently absorbed, reducing the initial content from 3.99 mg/L to <0.006 mg/L, achieving a notable 99.85% absorption.


Introduction
Water, a renewable natural resource, plays a crucial role in the life processes of living organisms [1].Groundwater, a prevalent source, often contains elevated levels of iron (Fe) and copper (Cu) [2].While small amounts of iron are essential for red blood cell formation, excessive levels can pose health and environmental risks [3].The World Health Organization (WHO) recommends that the Fe and Cu content in drinking water should not exceed 2 mg/L each for optimal health [4].Consequently, treatment of groundwater sources is frequently necessary before use.
In Indonesia, numerous remote areas encounter challenges in accessing clean water, particularly in North Sumatra, where well water often appears yellow or cloudy and contains detectable metal levels [5].Many residents, reliant on well water, express concerns about its quality, evident in the water changing color and emitting a metallic smell when left in a container.This study addresses these concerns by analyzing water samples obtained from a resident's house and revealing significant metal concentrations, particularly 8.06 mg/L of iron (Fe) and 3.99 mg/L of copper (Cu).Therefore, the primary objective of this research is to process the water to meet safe drinking standards.Consequently, this research aims to process the water to meet safe drinking standards.
To address the water quality concerns in regions dependent on wells, various techniques such as coagulation [6], membrane filtration [7], precipitation [8], ion exchange [9], adsorption [10], and chemical mixtures [11] can be employed.Among these, adsorption stands out as a widely used and effective method [12].Activated carbon, frequently utilized in adsorption, is chosen for its high surface

Application of Activated Carbon for Removal of Iron (Fe) and Copper (Cu)
Initially, the sample water was tested for iron (Fe) and copper (Cu) metals using Atomic Absorption Spectroscopy (AAS).Once the presence of iron (Fe) and copper (Cu) metals was confirmed, the water served as a sample to assess the absorption capability of activated carbon derived from rice husks.
For the filtration process, activated carbon was weighed according to the variations detailed in Table 1.The activated carbon was placed in separate test containers made of acrylic material, and the sample water was allowed to flow through the activated carbon in the arrangement illustrated in Figure 1.The base of the activated carbon was a Whatman filter paper to prevent any activated carbon from being carried along during the filtration process.Figure 1 Water filtration process with activated carbon One liter of water was passed through the filtration container, flowing through the activated carbon.Once all the water reached the container, it was collected and tested for levels of iron (Fe) and copper (Cu) metals using AAS.

Characterization
The characterization testing of activated carbon included Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX) testing to observe the morphology and structure.X-ray Diffraction (XRD) testing was conducted to identify the crystalline phases in the treated activated carbon.Simultaneously, the levels of iron and copper in water were determined using Atomic Absorption Spectroscopy (AAS).

XRD Analysis
The XRD patterns of the produced activated carbon are depicted in Figure 2, showcasing variations resulting from calcination temperatures of 700 °C, 800 °C, and 900 °C.Notably, the C900 sample stands out with a noticeable peak at a 2θ angle of around 23.97°.
Following a thorough analysis utilizing the ICDD database, specific observations surfaced for sample C900.The identification of the Miller Index (012) and the existence of a hexagonal crystal structure in this sample indicate a distinct crystalline composition.Conversely, samples C700 and C800 exhibit an amorphous structure, suggesting inadequate calcination temperatures.
The presence of a crystalline structure in sample C900 prompts intriguing reflections on how calcination temperature influences the activated carbon's attributes.Elevated temperatures, such as 900 °C, appear to promote the formation of a hexagonal crystal structure, as evidenced by the Miller Index (012) identification.This discovery aligns with prior research by [15], which highlights the tendency for the tridymite phase with a hexagonal crystal structure to develop within the temperature range of 900°C to 1000°C.Furthermore, the emergence of a hexagonal crystal structure in sample C900 suggests a more ordered arrangement of carbon atoms within the activated carbon matrix.This enhanced crystallinity could potentially lead to improved structural stability and surface area, which are crucial factors influencing the material's performance in various applications such as adsorption, catalysis, and energy storage.Additionally, the distinct crystalline composition observed in sample C900 underscores the significance of precise control over calcination temperature in tailoring the structural and chemical properties of activated carbon materials.These findings contribute valuable insights into optimizing the synthesis process to achieve desired material characteristics and enhance the overall performance of activated carbon-based systems.

SEM-EDX Analysis
The morphology of the obtained activated carbon, as revealed by SEM images in Figure 3, provides valuable insights into its structural characteristics.Figure 3a depicts the surface of activated carbon sample C700, showing a smoother surface with noticeable impurities on its pore surfaces.In contrast, activated carbon samples C800 and C900 (Figures 3b and c) exhibit uneven shapes but display fewer impurities on their surfaces.This observation suggests that higher calcination temperatures contribute to the removal of organic impurities, consequently increasing the surface area of the carbon.
According to [15], the calcination process results in a heterogeneously porous structure in activated carbon with emerging small crystal structures.The higher surface area and increased pore count enhance the activated carbon's potential as an adsorbent with improved quality.EDX testing was performed to assess the elemental composition of activated carbon derived from rice husk, a factor influencing its adsorption capacity (Table 2).The main elements identified in samples C700, C800, and C900 are carbon (C), silica (Si), and oxygen (O).Rice husk predominantly consists of cellulose, hemicellulose, lignin, and silica, with carbon being the primary constituent.During the carbonization process, organic components such as cellulose and hemicellulose decompose, leaving behind a carbon-rich residue.Additionally, the high silica content in rice husk contributes to the presence of silica in the activated carbon samples.The oxygen detected likely originates from residual oxygencontaining functional groups, as well as from silica and other inorganic compounds present in the rice husk.Understanding the elemental composition provides insights into the precursor material's transformation during activation of the activated carbon with its adsorption performance.2 reveals that a higher calcination temperature corresponds to an increased presence of carbon (C) elements in activated carbon.This directly impacts surface porosity, a critical factor influencing the adsorption capacity of activated carbon for gases or dissolved substances.The abundance of carbon elements regulates the type and size of pores in activated carbon.Additionally, trace impurities such as potassium were detected, which have the potential to cover pores, thereby reducing the adsorption capacity of activated carbon.

b c
Further analysis discloses that the Si/Al ratio in activated carbon samples from rice husks is highest at 35.This Si/Al ratio places the activated carbon in the category of intermediate adsorption capacity.Notably, a lower Si/Al ratio tends to render activated carbon more hydrophilic, emphasizing the interconnected relationship between elemental composition, surface properties of material, and adsorption capacity [11,16].

Absorption analysis of activated carbon as a filter for iron (Fe) and copper (Cu) in well water
The outcomes of the absorption process for iron metal (Fe) and copper metal (Cu) by activated carbon derived from rice husk, as determined through Atomic Absorption Spectroscopy (AAS), are meticulously presented in Table 3 and Table 4.The absorption efficiency of iron (Fe) from well water reaches an impressive 99.88% when utilizing each 4 g sample of activated carbon as the filtration material.This underscores the remarkable capability of activated carbon from rice husk waste to efficiently absorb iron (Fe) from well water.Figure 4 graphically illustrates the percentage of iron (Fe) absorption for each sample and Figure 5 graphically illustrates the percentage of copper (Cu) absorption for each sample.Notably, the absorption results for iron (Fe) in this study surpass those reported in a prior study by [17], where iron (Fe) absorption reached only 91.9% with a carbon amount of 50 g.The results further demonstrate the effectiveness of activated carbon from rice husk waste in absorbing copper (Cu) from well water, reaching an outstanding 99.85% at its maximum capacity.The absorption outcomes for copper (Cu) in this study surpass those documented in a previous study by [18], where copper (Cu) absorption was reported at 98.63% with a carbon amount of 2 g.These findings underline the superior adsorption capabilities of activated carbon derived from rice husk waste, positioning it as a promising and efficient filtration material for the removal of iron (Fe) and copper (Cu) from well water [19].The notable improvements in absorption percentages compared to prior studies underscore the potential impact of the synthesis and activation processes on enhancing the adsorption efficiency of the material.

Conclusion
Activated carbon synthesized from rice husk, with varying calcination temperatures of 700℃, 800℃, and 900℃ for iron (Fe) and copper (Cu) filters, has yielded promising results.XRD testing demonstrated an amorphous structure in samples calcinated at 700°C and 800°C, while a tridymite phase was formed in those calcinated at 900°C.SEM-EDX analysis showcased an increased surface area and a more refined pore structure attributed to high-temperature calcination.
AAS testing provided conclusive evidence of improved absorption performance for iron (Fe) and copper (Cu) metals.Notably, the activated carbon samples with a calcination temperature of 4 g exhibited optimal effectiveness.This configuration successfully reduced the initial iron (Fe) metal content from 8.06 mg/L to <0.009 mg/L, achieving an outstanding 99.88% absorption.Simultaneously, each 2 g sample, also with a calcination temperature, efficiently absorbed copper (Cu) metal, reducing the initial content from 3.99 mg/L to <0.006 mg/L and achieving an impressive 99.85% absorption.
These results underscore the efficacy of activated carbon from rice husk as a formidable adsorbent for iron (Fe) and copper (Cu) in well water treatment.The significant enhancement in absorption percentages, especially with smaller sample sizes, highlights the potential application of this synthesized material for efficient and scalable water purification processes.

Figure 2
Figure 2 XRD patterns of Activated Carbon

Figure 4
Figure 4 Graph of the percentage of iron (Fe) absorption

Figure 5
Figure 5 Graph of the percentage of copper (Cu) absorption

Table 1
Variation of activated carbon samples

Table 3
Test results and analysis of iron (Fe) metal absorption in well water samples

Table 4
Test results and analysis of copper (Cu) metal absorption in well water samples