Application of magnesium and biosurfactant functionalized biochar composite in treating cyanobacteria in phosphorus and crude oil contaminated water

Abstract

Various human activities have led to multiple contamination of natural water systems. The present study investigated the effect of a novel multifunctional biochar to treat nutrients, oil, and harmful algae in water. Specifically, magnesium (Mg) and biosurfactant rhamnolipid (RL) were incorporated into biochar, including Mg-biochar, RL-biochar, and Mg-RL-biochar. Their adsorption efficiency on phosphate and total petroleum hydrocarbons (TPH) was evaluated in separate batch studies. Also, the inhibition effect of RL-modified biochars on cyanobacteria was investigated. The results showed that Mg-impregnated biochar showed high adsorption capacity on phosphate (118 mg g⁻¹), while RL-modified biochar significantly reduced TPH (especially aromatic and light aliphatic fraction) with adsorption capacity of 44.4 mg g⁻¹. The inhibition effects of biochar composites on algae in water without contaminants were in order of Mg-RL-biochar > RL-biochar > biochar with biomass reduction ranging 61–64%. Overall, Mg-RL-biochar was  suggested based on this study due to its ability to remove PO₄³⁻ and TPH, and inhibit the growth of toxic algae.

Graphical abstract

Highlight

•	Mg-impregnated biochar showed high adsorption ability on PO43−.
•	RL-modified biochar showed high adsorption ability on TPH.
•	Mg-RL-biochar could remove PO43−, TPH, and inhibit toxic algae.

Funding

Yunnan Fundamental Research Projects(202201BE070001-043)

National Natural Science Foundation of China(41967039)

Yunnan Provincial Excellent Young Scientists Fund(202201AW070006)

Yunnan Foundation Research Projects(202301AU070074)