Researchers, led by Pamodithya Wijeyawardana, have developed a promising solution to the persistent problem of heavy metal contamination in urban stormwater. In a study published in the June 2024 issue of Process Safety and Environmental Protection, the team explores the efficacy of Ordinary Portland Cement (OPC) modified biochar as an adsorbent for copper (Cu), lead (Pb), and zinc (Zn).

The study found that introducing a small amount (1.5% v/v) of OPC to biochar significantly boosts its adsorption capacity, making it 3.3, 2.4, and 6 times more effective for Cu, Pb, and Zn removal respectively, compared to its unmodified counterpart. This enhanced performance can be attributed to the synergy between biochar’s functional groups and the hydrated OPC, which form a robust composite capable of binding heavy metals effectively.

According to the research, the Langmuir monolayer adsorption model accurately described the adsorption process, with heavy metals binding to various functional groups like carbonyls, carbonates, and silanols. Notably, the modified biochar showed adsorption capacities comparable to commercial activated carbons, reaching 28.82 mg/g for Cu, 38.76 mg/g for Pb, and 26.53 mg/g for Zn.

The study also delved into the impact of competing ions and nutrients on heavy metal removal. Surprisingly, nitrates had negligible effects, phosphate ions enhanced Pb removal, ammonium ions slightly reduced removal efficiency for all metals, and humic acid increased overall removal.

These findings underscore the potential of OPC-modified biochar in practical applications for cleaning urban stormwater. By improving the efficiency of heavy metal removal, this innovative composite addresses a critical environmental issue, paving the way for safer urban waterways and a reduced burden of pollution on natural ecosystems and human health.