The Effect of Incubation Time and Drainage pH on the Immobilization of Copper in Post Coal Mine Soil Using Sumatera Brown Coal Char

Post coal mine (PCM) activities pose significant environmental challenges. Soils affected by PCM often exhibit increased acidity and elevated levels of heavy metals. In the case of Sungai Buluh PCM in the Jambi Province, Indonesia, copper (Cu) levels in the soil reach 94.79 mg kg-1, surpassing the Indonesian standard of 40 mg kg-1. Sumatera brown coal (SBC), typically is not considered as fuel due to its properties, offers a cost-effective solution for Cu immobilization in such soils. In this study, SBC was subjected to pyrolysis at 400°C for 1 h, sieved through a 10-mesh sieve, and characterized using SEM and FTIR. The soil-char mixture consisted of 250 g of soil and 25 g of char (9:1 ratio), while a control group included 250 grams of soil with no char. The soil's pH significantly influenced Cu adsorption by SBC char. Cu immobility by SBC char was highest at pH 5, with an efficiency of 66.67% from pH 1 to 5. Over a 4-week period, the mobility of Cu in soil containing 10% char decreased by 36.36%. Pseudo-first-order kinetics yielded R2 values of 0.750 and 0.979 for 0% and 10% char additions, respectively. To inform future research on SBC char's potential for soil amendment, exploring the properties of SBC char produced at different pyrolysis temperatures is advisable. This information can aid in the development of char furnaces with appropriate technology to efficiently produce large quantities of effective SBC char. Additionally, determining optimal incubation times can help predict the frequency of char application in various regions.