Enhanced Wastewater Purification Using Biochar, Activated Carbon, and Kaolinite Composites: A Multi-Parameter Approach for Sustainable Agriculture

Rising population pressures have intensified the need to reuse wastewater, which increases exposure to microbial and heavy metal contamination, negatively impacting ecosystems and human health. Heavy metals in wastewater present a major environmental concern. This study examines the adsorption capacities and efficiencies of individual and combined adsorbents—activated carbon (AC), biochar (BC), and kaolinite (KA)—for removing heavy metals, organic matter, salinity, and pathogens from wastewater. Wastewater samples were treated in column adsorption systems and analyzed before and after treatment using physicochemical and microbiological methods. The composite adsorbent (AC + BC + KA) performed best, reducing electrical conductivity by 75% (from 4.0 to 1.0 mS/cm), total dissolved solids from 2560 mg/L to 915.2 mg/L, and sodium adsorption ratio from 27.14 to 7.06. The pH remained within the optimal irrigation range (7.66). The system removed up to 85.87% of heavy metals (Cu 2+ , Cd 2+ , Mn 2+ , Zn 2+ ) and 100% of pathogenic bacteria ( E. coli , Shigella spp., and B. cereus ). The microporous structure of AC provides large surface areas for pollutant trapping through adsorption, while BC introduces functional groups that enhance contaminant capture. The combination of these materials offers an eco-friendly and effective method for wastewater purification.