Abstract:
Problem definition and objectives: Due to the escalating depletion of forest resources and growing environmental concerns, the recycling and reuse of consumable materials, such as cellulosic filters used in water filtration, have emerged as sustainable and economically viable strategies for producing new raw materials. This study investigates the recovery of spent cellulose filters from the petrochemical industry to produce high-purity cellulose powder, aiming to optimize leaching and acid washing processes to enhance efficiency and minimize impurities. The research addresses the critical need for sustainable practices in industries reliant on cellulosic materials, offering a pathway to reduce waste and environmental impact while creating value-added products.
Methodology: The methodology involved a two-stage treatment process. Initially, used filter samples were washed with distilled water (pH 6-7, 50 mL) to remove surface contaminants. Subsequently, the filters underwent acid washing with a 2% hydrochloric acid (HCl) solution at ambient temperature for 30 minutes. For comparison, sulfuric acid (H₂SO₄) was also tested. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis revealed that the untreated filters contained significant amounts of calcium (366 mg/L), iron (70.1 mg/L), sodium, and heavy metals such as cadmium (6.1 µg/L), lead (2.6 µg/L), and uranium (5.4 µg/L), underscoring their efficacy in water filtration but necessitating their removal for reuse. Post-treatment, HCl effectively reduced these elements, lowering the residual ash content to approximately 0.24%, compared to higher ash residues with H₂SO₄ due to the formation of insoluble precipitates like CaSO₄.
Results: Advanced analytical techniques, including X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), and Field Emission Scanning Electron Microscopy (FESEM), were employed to characterize the treated cellulose. XRD confirmed an enhanced crystalline structure, with characteristic peaks at 2θ=22.7° and 2θ=18°, indicative of pure cellulose I. TGA demonstrated improved thermal stability, with cellulose decomposition occurring between 300–395°C, attributed to the removal of amorphous components like lignin and hemicellulose. FESEM images revealed better fiber separation, increased porosity, and a cleaner surface, enhancing the material’s suitability for downstream applications. Standard tests (R10 and R18) and Water Retention Value (WRV) measurements further validated the quality of the recovered cellulose, with R10 and R18 values of 50 and 60, respectively, indicating high reactivity and low impurities, and a WRV of 78.81%, suggesting excellent water retention for applications in pulp, paper, or as a biosorbent.
Statistical analysis using Design-Expert software and Response Surface Methodology (RSM) evaluated the effects of variables such as temperature, time, acid type, and concentration. Temperature and acid concentration were identified as the most influential factors affecting yield and purity. HCl outperformed H₂SO₄ by forming soluble compounds like CaCl₂, which facilitated impurity removal. The optimal conditions involved 2–5% HCl for 30 minutes, balancing effective impurity elimination with the preservation of cellulose structure.
Conclusion: In conclusion, this research demonstrates that spent cellulose filters can be efficiently recycled into high-purity cellulose powder, offering significant environmental and economic benefits. The process reduces waste, conserves natural resources, and provides a sustainable raw material for industries such as pulp and paper, viscose production, and biosorption. The findings highlight the potential for industrial-scale implementation, contributing to a circular economy and addressing global environmental challenges. This study underscores the importance of innovative recycling strategies in mitigating the environmental impact of industrial filtration systems.