Recovery of sugarcane bagasse as adsorbent for chromium (Cr) (III) removal

The aim of the study was to explore the ability of bioactivated carbon on Cr III removal. Chromium (III) is one of the heavy metals, toxic and harmful for human being causing spread pulmonary fibrosis disease. Adsorption is one of the alternatives and an effective purification and separation technique used in industrial wastewater treatment. Bioactivated carbon was obtained from sugarcane bagasse based agricultural biomass waste by furnace dried carried out at 400°C for 2h, activated by chemical using phosphoric acid. Bioactivated carbons were used to treat chromium (III) from artificial wastewater containing chromium. Cr (III) removal was investigated by the batch process with adsorbent dose, contact time and particle size to finding optimum conditions as an experiment variable. Bioactivated carbon resulting have surface area of 309.44 and 3133.82 m2/g, respectively for sizes 150 and 200 mesh using BET measurement. The predominance of carbon achieving 80.24%, 18.68% and 1.08% respectively for element C, O and Si, identified by SEM-EDX analyser. The optimum condition of the batch adsorption achieving 99.9% chromium removal, resulting from operation condition in 30 minutes contact time using 6 g adsorbent 200 mesh.


Introduction
Chromium (Cr) is one of the heavy metals in the water environments has potential to cause physiological disorders in phytotoxicity as well as organisms [1].Chromium is difficult to treat from aquatic environment and the most toxic heavy metals, has potential impact in environmental sustainability and human health.Chromium compounds are mostly used in the tanning, electroplating, dyeing industries and metallurgical.Industrial process using chromium resulting Cr 3+ and Cr 6+ founded in aquatic environment.Chromium ion has ability to receive and denote electrons, being substances that are oxidants or reducing agents.Chromium was relatively more difficult to treat by traditional treatment.
Promising technology to remove chromium (III) ions was a simple adsorption [2].Adsorption is mostly suggested as promising technology for removing contaminants in low concentrations [3]- [5] The important point of developing adsorbents is to improve the adsorption capacity.The adsorption process conducted in surface reaction.A high surface area is frequently needed as an essential parameter to increase the adsorption capacity [6], [7].Activation process is a essential step to produce activated 1265 (2023) 012006 IOP Publishing doi:10.1088/1755-1315/1265/1/012006 2 carbon with higher capacity adsorbent.Activation process could utilize phosphoric acid as promising activator in chemical activation.In general, phosphoric acid has been reported to be the most effective activated carbon from agricultural waste [8].Bioactivated carbon can be utilizing natural materials as well as based agricultural waste including tea waste, sunflower stalk, pine cones, wood, rice waste, straw, sugarcane bagasse, corn waste, durian seed and coconut shell [8]- [13].

Methodology 2.1 Preparation bioactivated carbon
As reported by [14], bioactivated carbon derived from sugarcane bagasse.The collected wet sugarcane bagasse was grinded or chopped; sun-dried; furnace dried at 400°C for 2 h, activated by using Phosphoric Acid.Carbonated bagasse was crushed and sieved using 150 and 200 mesh.

Bioactivated carbon characterization method
Morphological analysis of bagasse carbonation was carried out using Scanning Electron Microscope (SEM-EDX), Brunauer-Emmett-Teller Analyzer (BET), while quality analysis was carried out based on Indonesian National Standard (SNI).

Adsorption batch and determination of Cr (III) concentration in water solution method
This study aims to analyze the batch process optimal conditions of several research variations, namely contact time (30, 45, 60, 75 minutes), particle size (150 and 200 mesh), and adsorbent mass (3, 6, 9 g).Samples of artificial waste containing chromium concentrations of 50 ppm at 250 mL will be processed based on each variation of the study.Chromium (III) was analyzed by spectrophotometry.

Bioactivated carbon characterization
Bioactivated carbon resulting from sugarcane bagasse analysing using SEM to investigate the morphology, BET to identify the surface area and SNI to compare with Indonesia quality standard of activated carbon.

Textural characterization
The size of pores formed would have an effect on the total surface area which is available for adsorption, the porosity, and the most important is the size of molecules that can diffuse into the solid.Porosity is strongly influenced by temperature in carbonation process.Increasing temperature in the carbonization process, resulting fresh micropores formation which increasing the micropore volume of activated carbon and BET surface area.The higher BET surface area indicates the existence of a significant amount of microporosity [13].Activation can be conducted using physical and chemical process.
In general, the activation process using chemical treatment consist of carbonizing and activating material simultaneously by adding chemical activation agents.Oxidizing and dehydrating agents are most often used for chemical activation in carbonization.Zinc chloride is the most frequently used in chemical activation and more friendly to the environment.Another chemical activator that is also often used to produce activated carbon is phosphoric acid which has a high level of effectiveness [8].
As reported by [14], bioactive carbon from bagasse produced using the phosphoric acid activator, can provide activated carbon which has a surface area of 309.44 and 3133.82m 2 /g, respectively for sizes 150 and 200 mesh.Previous research reported activated carbon resulting from durian seed using furnace dried at 600-900°C, the most popular carbon which achieving at 2,123 m 2 /g in the highest surface BET [8].As reported by [13], sugarcane bagasse heated up at 20°C under the nitrogen gas flow with carbonation temperature of 400, 600 and 800°C for 2 hours resulting surface BET of respectively 225.27, 405,81 and 661.46 m 2 /g [13].Compared with the previous research, sugarcane bagasse activated carbon resulting from this study has a surface BET higher than an existing experiment.Activated production from recovery waste using sugarcane bagasse potentially success achieved a higher surface area because supported by the chemical activator process added.

Chemical characterization
Chemical characterization was represented by elemental analyses of sugarcane bagasse carbon.The results show the presence of many elements with predominance of carbon achieving 80.24%, 18.68% and 1.08% respectively for element C, O and Si [14].Carbon percentage increased after carbonization and activation process.These increases in carbon percentage are important due to the loss of volatile matter and cellulose and hemicellulose decomposition during pyrolysis.Lignin decomposition occurs at activation process [8], [13].Scanning Electron Microscope of the surface morphology reported in Figure 1.From this figures, it is clear that the activated carbon resulted has cavities on their external surface.As reported by [8], [14], it shows that the cavities on the carbon surfaces resulted from the evaporation of the activating agent using phosphoric acid in carbonization process, leaving the space previously occupied by the activating agent.

The optimum condition of batch adsorption process
Batch adsorption process conducted using artificial sample containing chromium concentrations of 50 ppm at 250 cc.Artificial sample will be processed based on each variation of the study.Three absorbent mass dose (3, 6 and 9 g) were conducted in order to find out the optimum dosage in adsorption treatment to remove chromium.Combined with four contact time variations and the size of particle, results of investigation can be shown in Figure 2 and Figure 3.As shown from Figure 2 and 3, almost all variation resulting percent efficiency removal achieving more than 95%.Using of activated carbon from sugarcane bagasse mesh 200 can produce a percent removal efficiency of up to 99%.As reported by [15], [16] the specific surface area and the pore volume of activated carbon increase significantly as the particle size decreases.The main objective of developing adsorbents is to improve the adsorption capacity.The adsorption process is a surface reaction, a high surface area is often seen as an important characteristic to improve the adsorption capacity [6], [7].The 200mesh sugarcane bagasse adsorbent has a higher surface area compared to 150 mesh, potentially causing a larger removal percentage due to the larger adsorption capacity as well.The optimum condition of the batch adsorption process was conducted using 30 minutes contact time with 6 g adsorbent 200 mesh, resulting in 99.9% chromium removal.

Figure 2 .Figure 3 .
Figure 2. Variation of dose and contact time using 150 mesh