Table 3.

Summary of the advantages and limitations for some of the alternative treatment technologies for herbicides.

Technique	Brief description	Advantages	Limitations	‘Green’ rating (1–5)	References
Herbicide substitution via allelopathy effect	Use plant extracts (Nerium, olives, etc.) as biological control of weeds	Natural resource Eco-friendly Pollution-free	Unknown ecological and physiological properties Limited to small scale	5	[114]
Nano bioremediation	Mineralization of herbicide compounds by microorganisms (e.g. F. mosseae, Pseudomonas strains) through hybrid nanomaterial-microbial remediation technique	Eco-friendly Low energy consumption Low operating cost Large-scale application	Slow rate of biodegradation Nanomaterials may bring negative effects to the environment and microbial activity. Poor recyclability, loss of microorganisms and nanomaterials High post-processing cost (incineration)	4	[96]
Electrochemical advanced oxidation	Herbicide molecules are broken by electrochemically produced reactive oxygen (hydroxyl radical) at the electrode surface (e.g. anodic oxidation, electro-Fenton, photoelectrocatalysis, etc.)	High efficiency Easy operation Harmless end products Able to mineralize less biodegradable atrazine	Energy-intensive process powered by electricity (high operating cost) Recalcitrant, toxic by-products/intermediates Limited to synthetic herbicide in small bench-scale	3	[10]
Functionalized biosorbent	The surface chemistry of biosorbent derived from biomass is altered by specific functional groups to entrap herbicide molecules through electrostatic attraction, complex formation, etc.	Natural resource High adsorption capacity Recyclability of material	Use of chemicals during synthesis and reactivation Limited to bench-scale Performance varies depending on the types of herbicides.	4	[121]
Advanced photocatalyst	Nanomaterial that absorbs light (photocatalysis process) to generate electron-hole pairs that promote redox (degradation) reactions of herbicide molecules into harmless compounds	High degradation performance Recyclability of material	Low quantum yield Very specific light source Toxic intermediates Leached nanomaterial may bring negative implications to environmental and public health	3	[120]