Conversion of crop, weed and tree biomass into biochar for heavy metal removal and wastewater treatment

It was quantified the influence of four different biomasses viz. tree, weed and crop on twenty compositional characteristics of produced biochar for their wide range of environmental application. The removal of most widespread heavy metal ions (cadmium (Cd), lead (Pb), nickel (Ni), zinc (Zn), copper (Cu) and arsenic (As)) by adsorption on four biochars has been investigated. Initial evaluation revealed that all the biochar was efficient in removing a mixture of six heavy metals from aqueous phase having maximum removal for arsenic and minimum nickel. Utilizing four different biochars, the average removal rate of heavy metal from aqueous solution was 49.5-66.1% (Cd), 47.3-60.0% (Pb), 45.5-60.6% (Ni), 46.6-60.8% (Zn), 49.3-63.2% (Cu) and 52.7-64.2% (As) compared with no biochar treatment. The percent decrease of Pb heavy metal adsorption with increase in maximum contaminant level (MCL) from 1- to 5-fold was 54.7 (black gram biochar), 53.5 (pine needle biochar), 52.02 (Lantana camara biochar) and 50.0 (maize stalk biochar). The effect of dose study showed that As adsorption on all the four types of biochar was most favourable and Ni adsorption was the most awful. At the bio-filtration stage, the wastewater was treated with four different biochars and the physico-chemical character changes were recorded before and after treatment with biochar. The wastewater total chemical oxygen demand, total soluble solid, ammonia, total potassium and nitrogen and total potassium values demonstrated an 88.3-90.6%, 84.8-81.1%, 90.9-86.6%, 58.8-69.3% and 88.1-77.96% decrease, respectively. Additionally, the wastewater As, Cd, Cr, Pb, Zn and Cu values resulted a 78.5-86.5%, 52.6-94.7%, 83.1-88.1%, 94.6-77.8%, 90.1-94.5% and 93.3-95.5% decrease, respectively, after being passed via biochar bio-filter. Therefore, the four developed biochar explored huge potential for removal of heavy metal along with wastewater treatment to meet guidelines for wastewater effluent disposal.