Co-transport and Retention of Arsenic and Pine Wood Biochar in Saturated Porous Media: Fate and Interaction Mechanisms under Solution Chemistry and Practical Feasibility

Geogenic arsenic (As) contamination in groundwater causes serious health and environmental concerns. Anthropogenic actions also contaminate natural ecosystems, including groundwater aquifer systems, with As severely impacting human health and ecosystems. Considering practical feasibility and sustainable water management, this research work aims to determine the adsorptive properties of pine wood raw biochar (PWBC) and engineered iron-modified biochar (Fe-PWBC) in As(V) removal. Co-transport and deposition of As(V) with PWBC and Fe-PWBC were investigated in saturated columns, and experimental data were modeled using HYDRUS-1D to determine effective As removal in the managed aquifer recharge technique. Sand-packed saturated columns lead to high As(V) deposition at an ionic strength (IS) of 0 mM, whereas an IS of 10 mM mobilizes As(V) at pH 6.7 ± 0.1. Considering co-transport, the adsorptive behavior of PWBC and Fe-PWBC were analyzed for 5–10 mg/L As(V) under varying pH (5.5 ± 0.1 to 10.5 ± 0.1), IS (0–10 mM), As(V) concentrations (5–10 mg/L), and biochar dosages (50–100 mg/L). Significantly, increased biochar deposition was observed with increased IS due to aggregation and ionic effects, and Fe-PWBC showed higher potential As(V) adsorption compared to PWBC. Understanding the fate and remediation of As in saturated porous media is crucial for developing effective remediation techniques. Overall, Fe-PWBC acts as a better carrier for As(V) in saturated porous media and facilitates adsorption onto its active sites than PWBC during co-transport and deposition governed by solution chemistry. Lastly, this work concludes with implications of biochar use in aquifer recharging and biochar-sand-packed fitting in hand pumps for groundwater recharge and safe drinking water supply.