Northern white-cedar biochar as an effective adsorbent for lead (II) ion removal from groundwater: a promising environmental strategy

• Pb exceeds the recommended limits in the groundwater of Bilaspur. • Biochar derived from Thuja occidentalis applied for the removal of Pb. • Exceptional characteristics of biochar (700 °C) favored Pb removal. • Pb remediation of 98.7 % was achieved utilizing the Box-Behnken design. In recent times, the issue of groundwater contamination by metals has become a cause for concern due to their harmful properties and ability to build up in the environment. A study was conducted to evaluate the quality of groundwater in Bilaspur (Chhattisgarh), India, using standard methods. The results showed that lead (II), was the most prevalent metal found, with around 33.3 % of groundwater samples exceeding the recommended limit of 10 ppb for Pb levels as prescribed by the World Health Organization (WHO). This highlights the extensive Pb contamination in the groundwater of Bilaspur, Chhattisgarh, India. The toxicity of the water was determined through germination tests on Phaseolus mungo , which confirmed a decrease in germination and amylase activity. This study suggested the potential use of biochar made from Thuja occidentalis as a cost-effective material to remove Pb from water. The Thuja occidentalis biochar was characterized using SEM-EDS and FTIR techniques. A series of batch adsorption experiments using the Box-Behnken design (BBD) revealed that the biochar was effective in removing the metal at different concentration levels (10 ppb to 50 ppb for lower levels and 100 ppb to 500 ppb for higher levels) in both spiked and real samples. By employing a quadratic model, it was found that a contact time of 80 min, a pH of 6.0, and a stirring speed of 200 RPM were the optimal conditions for Pb removal, achieving a removal rate of 98.7 %. Thuja occidentalis biochar displayed capabilities as a natural material for the efficient removal of Pb through adsorption.