Conversion of industrial carpet waste into adsorbent materials for organic dye removal from water

Abstract

The vast amount of carpet waste produced from the manufacturing processes is dumped in landfills, causing environmental issues and problems. In addition to recycling and reuse processes, the conversion of carpet waste into a higher value-added product is an interesting option to manage carpet waste with the most benefits and values. This work highlights the conversion of industrial carpet waste into alternative adsorbents for dye removal. The pre-consumer carpet waste was pyrolyzed at different temperatures ranging from 500 to 900 °C under argon flow. Due to the high fraction of calcium carbonate (CaCO3) filled in the adhesive layer in carpet, CaCO3 was acquired at 500 and 600 °C, while the calcium hydroxide (Ca(OH)2) with a hexagonal platelet-shaped crystal began to form at 700 °C. In addition to CaCO3 and Ca(OH)2, carbon was also found in the samples due to the carbonization of the polymeric fibers and backings. The specific surface area increased with increasing pyrolysis temperature ranging from 15 to 26 m2 g−1 with a predominance of mesopores. Potential utilization as dye adsorbents was evaluated using methylene blue (cationic dye) and methyl orange (anionic dye) at concentrations of 10, 15, and 20 mg L−1. Among all samples, the carpet waste pyrolyzed at 900 °C showed the highest adsorption efficiency of about 100% for methylene blue and 93–99% for methyl orange at the dye concentration of 10–20 mg L−1. The lower adsorption efficiency of methyl orange was due to the effect of electrostatic interaction between the dye molecules and adsorbent surface. The results in this work offer useful information for converting carpet waste into alternative dye adsorbents towards sustainable water management.

Keywords

• Carpet waste
• Pyrolysis
• Dye adsorbents
• Calcium carbonate
• Calcium hydroxide