Use of Biochar Obtained from Pyrolysis of Waste Filter Coffee as Adsorbent for Nickel Removal

Filter coffee consumption is widespread globally and has gained significant popularity across Turkiye in recent years. Waste filter coffee (WFC) produced daily in filter coffee chains is directly disposed. The economic and environmental costs of disposing of WFC in this way are high, and therefore alternative methods are needed for the recycling of this organic waste. In this study, biochar recovery from WFC pulp by pyrolysis method and effectiveness of biochar as an adsorbent were investigated. Since the surface area of a biochar obtained by pyrolysis of WFC were too small to be measured, carbonization process was carried out at 900 °C for 4 h. After the carbonization process, the biochar reached a surface area of 44.59 m²/g. Additionally, while the carbon (C%) content in the raw WFC was 50.84%, it increased to 81.53% after carbonization. At the same time, the solid content rose from 91.72 to 96.55%. The enhanced properties of the biochar, particularly the increased surface area and carbon content, have facilitated its investigation as an adsorbent. Nickel removal by adsorption from nickel solution prepared synthetically with biochars obtained after carbonization was investigated. It was determined that nickel adsorption with WFC biochar could be best expressed by Langmuir isotherm (q_m = 6.54 mg/g) and could be kinetically described by pseudo-second order equation (R² value varies between 0.96 and 1).