Bentonite-assisted carbonisation of waste polyethylene terephthalate bottles for the removal of heavy metals from polluted water

Polyethylene terephthalate (PET) plastic pollution is a significant environmental concern. PET is a common type of plastic used in the production of items such as beverage bottles, food packaging, clothing fibres, and more. When not properly disposed of or recycled, PET plastic can contribute to pollution in various ways. Water pollution is also one global issue which is affecting both human and animal lives. In most developing countries, water bodies are being polluted by heavy metals as a result of industrial activities and other anthropogenic activities which make the water unsafe for drinking. Activated carbon was produced from shredded waste PET bottles for the removal of cadmium, mercury, arsenic, lead and nickel from polluted water sample from River Oda in Ghana. Bentonite clay was modified by acid activation technique to act as a catalyst to assist the carbonisation of the shredded waste PET and to investigate its effect on the yield of the carbon. The bentonite catalyst was added to the shredded PET samples in varying amounts 0-10 wt% with 2 wt% increment. The resulting carbonized solid product (char) was then activated with potassium hydroxide. The obtained results after the carbonisation showed that bentonite catalyst improved the yield of the carbon proportionally. The percentage yield increased from 19.08 f 0.001% to 30.24 f 0.005% as the catalyst was added in varying amounts 0-10 wt% with 2 wt% increment. The AAS results depicted that the five heavy metals analysed in this work had concentrations above the allowable limits in drinking water and hence showed that the River Oda in Ashanti Region of Ghana is highly polluted and unsafe for drinking by both humans and animals. The removal efficiencies with respect to adsorbent dosages for the adsorption mechanism of the five heavy metals were also investigated and it was observed clearly that they were directly related. The produced activated carbon had the tendency or proclivity to eliminate the heavy metals from the polluted water. Cd elimination rose from 81.63 f 0.56% to 98.70 f 0.63% as the adsorbent dosage was increased from 0.5 to 2.5 g. With the increase in adsorbent weight, Hg removal rose from 95.14 f 0.10% to 99.30 f 0.10%. Also, increase in adsorbent weight, Pb removal rose from 84.17 f 0.75% to 98.99 f 0.50%. Removal rose from 68.65 f 0.77% to 79.36 f 0.31% as adsorbent weight increased for Arsenic removal. With the increase in adsorbent weight, Ni removal rose from 70.59 f 0.59% to 97.06 f 0.74%.