Preparation and Characterization of Cocoa Shell - Pahae Natural Zeolite as a Metal Adsorption Material for Iron (Fe) and Manganese (Mn) in Water

Research has been conducted on an adsorber made from cocoa shell activated charcoal and Pahae Natural Zeolite, designed as an absorber for Fe and Mn metals in well water purification. The cocoa shell were screened with a 100-mesh sieve, followed by carbonization to generate activated charcoal. In parallel, Pahae Natural Zeolite underwent a similar sieving process with a 100-mesh screen and was subsequently chemically activated using a 2.5 M NaOH solution. The compositions of the cocoa shell activated charcoal - Pahae Natural Zeolite adsorber were varied as follows (wt%): 100:0, 95:5, 90:10, 85:15, 80:20, 75:25. These mixtures were then compressed using a hydraulic press with a load of 6 tons for a duration of 10 minutes. The resulting samples underwent physical activation at different temperatures (300°C, 320°C, 340°C) for 30 minutes. The adsorber was subjected to characterization to ascertain its physical properties (porosity, adsorption capacity, density), mechanical properties (compressive strength and hardness), surface morphology, and elemental composition (SEM-EDX). The outcomes of the tests demonstrated the efficacy of the cocoa shell activated charcoal - zeolite based adsorber in significantly reducing iron (Fe) and manganese (Mn) levels, with a remarkable reduction in Fe content by 99.76% and Mn content by 99.70%.


Introduction
Water, essential for life, involves various molecular-level aspects that remain incompletely understood.It assumes diverse roles across different levels of complexity, spanning from molecules and cells to tissues and organisms [1][2][3][4].Despite advancements in water treatment technologies, a significant portion of the global population relies on well water as a primary source of clean water.However, well water is highly susceptible to contamination through seepage, elevating concentrations of various chemicals, including manganese, iron metals, and organic materials [5].According to the 2017 water quality standards set by PERMENKES, iron metal concentrations should not exceed 1 mg/L, while manganese (Mn) levels should not surpass 0.5 mg/L [6].
One effective method for water treatment is adsorption, offering advantages such as straightforward operation, relatively high efficiency, and the absence of associated side effects in the form of toxicity [7].Adsorption using activated carbon, widely adopted for water purification and the reduction of water hardness, is due to its exceptional adsorption capacity stemming from its porous structure and large surface area.Cocoa pod shells (Theobroma cacao L) present a promising adsorbent in this context [8].Zeolite, characterized by an abundance of pores and channels, is another effective adsorbent.The cylindrical shape of zeolite's pores and channels enhances its surface area, and greater pore density corresponds to increased overall surface area [9][10][11][12][13][14].A prior study demonstrated the efficacy of cocoa husk adsorbent in reducing iron (Fe) and manganese (Mn) content by 97.59% and 90.95%, respectively [15].Zeolite adsorbents have shown the ability to reduce iron by 95.4%, copper by 96.0%, and chromium by 85.1% at a temperature of 25.0°C and a pH level of 4.0 [16].
In this investigative study, our objective is to develop an adsorber utilizing activated charcoal derived from cocoa shells and zeolite.The resulting adsorber will serve as a means to diminish the levels of iron (Fe) and manganese (Mn) in turbid, discolored, and malodorous well water.This reduction will be accomplished through the adsorption process.We will evaluate diverse parameters, encompassing pH, temperature, taste, odor, color, turbidity, dissolved solids, as well as concentrations of Fe and Mn metals.

Material
Pahae Natural Zeolite was sourced from Pahae Subdistrict, North Tapanuli, North Sumatra, Indonesia.Cocoa shells were obtained from Sukaramai Village, West Binjai, Binjai City, North Sumatra.NaOH and distilled water were used in the process.

Preparation of Adsorber
The cocoa shells, yellow in color, were cleaned and dried before being carbonized at 150°C for 1 hour to produce activated carbon.This was then ground and sieved through a 100 mesh screen.Similarly, Pahae natural zeolite, also sieved to 100 mesh, underwent chemical activation with a 2.5 M NaOH solution.The filter was created by mixing the activated carbon with zeolite in various compositions (A: 100:0, B: 95:5, C: 90:10, D: 85:15, E: 80:20, F: 75:25 % wt).After molding, the samples were left to pre-sinter in open air for a week, followed by physical activation at temperatures of 300, 320, and 340 ℃ for 30 minutes.

Porosity Testing
Material porosity was assessed in accordance with ASTM C-373-88-2006.It was determined by measuring the sample's weight before and after immersion in water and subsequently calculating both the sample volume and water density.

Water Absorption Testing
Material water absorption was assessed in accordance with ASTM C-20-00-2005.This measurement was obtained by weighing the sample before and after immersion in water.

Density Testing
The density of the sample was evaluated following ASTM C 373-88-2006.This measurement is determined by measuring the volume of the sample before immersion in water.

Compression Strength Testing
The compressive strength of the material was assessed using a Tensilon brand Universal Testing Machine.This can be calculated after the completion of the sample testing.

Hardness Testing
The hardness of the cocoa-zeolite activated charcoal adsorber was assessed using the Tokyo Vickers Hardness test.This measurement can be calculated after the sample has been tested.

Porosity Testing
Figure 1 displays the porosity test results.The 75%:25% adsorber composition shows the highest porosity (54.22%) at 340°C, while the 100%:0% composition exhibits the lowest (23.38%) at 300°C.Zeolite filler increases porosity, but as the adsorber temperature rises, porosity decreases due to smaller and progressively closed pores, resulting in denser pore diameters.Figure 2 shows that the 75%:25% adsorber composition at 340°C has the highest water absorption at 89.54%, while the 100%:0% composition at 300°C has the lowest at 26.54%.The addition of zeolite enhances water absorption, directly proportional to porosity.Higher temperatures reduce water absorption due to increased pore coverage on the adsorber's surface, limiting pore distribution.

Density Testing
Figure 3 shows density testing results for the cocoa-zeolite shell activated charcoal adsorber.The highest density, 0.883 g/cm³, occurred at 100%:0% composition and 300°C, while the lowest, 0.60 g/cm³, was at 75%:25% composition and 340°C.Impurities during combustion, even in a vacuum, contribute to reduced density in the adsorber material.4 demonstrates that compressive strength decreases with higher combustion temperatures, attributed to increased porosity.Under optimal conditions at 300°C, the adsorber shows high compressive strength at 36.462 MPa.Conversely, less optimal conditions at 340°C result in lower compressive strength at 2.243 MPa, influenced by decreasing density.

Hardness Testing
Figure 5 shows hardness testing for the cocoa shell-zeolite adsorber.The highest hardness, 385.672MPa, occurred at 100%:0% composition and 300°C, while the lowest, 116.789MPa, was at 75%:25% composition and 340°C.With increasing combustion temperature, hardness tends to decrease.It's noteworthy that hardness results have an inverse relationship with physical properties, indicating that the addition of zeolite filler does not increase hardness.

Water Purification
The cocoa shell-zeolite activated charcoal adsorber effectively reduced the initial iron (Fe) content from 17.8189 mg/L to 0.0578 mg/L (99.67% reduction) and manganese (Mn) content from 0.8376 mg/L to 0.0276 mg/L (99.70% reduction) in water purification testing.

Conclusion
The cocoa shell-zeolite activated charcoal adsorber produced in this study has a higher water absorption capacity of 89.54%, which indicates the ability of the adsorber to absorb water.The presence of modernite in the Pahae natural zeolite was validated by the Si/Al ratio from the EDX study.The hardness values of the activated samples show that the sample which was activated at temperatures of 340 °C was the sample that has the optimum hardness value.During water purification, cocoa shell-zeolite activated charcoal filter effectively absorbs Fe and Mn metals, as evidenced by a 99.67% reduction in Fe and 99.70% reduction in Mn in well water testing.

Figure
Figure4demonstrates that compressive strength decreases with higher combustion temperatures, attributed to increased porosity.Under optimal conditions at 300°C, the adsorber shows high compressive strength at 36.462 MPa.Conversely, less optimal conditions at 340°C result in lower compressive strength at 2.243 MPa, influenced by decreasing density.

Table 1 .
Analysis Results for Water Purification