A comprehensive review on the selection of plant's part as coagulant for water/wastewater treatment

• Plant biocoagulants show promise in replacing chemical coagulants effectively. • Plant biocoagulants are superior in removing turbidity. • Seeds showed a high average removal of turbidity. • The plant extract also showed a high average removal. • Conducting species-specific analysis is suggested as future research. The use of plants as biocoagulants in water/wastewater treatment is currently emerging. This review article explores the potential of each plant’s part functioning as a biocoagulant for pollutant removal. Bibliometric analysis was employed to analyze the development of research in natural and biocoagulants, while descriptive analysis was used to clearly juxtapose the performance of each plant’s part in treating water/wastewater. Bibliometric findings reveal a high increment in the publication of natural coagulants in the year 2016. The keywords of flocculation, pH, turbidity, and water purification are mentioned to be the closest node related to the coagulation. Comparison between plant parts showed that research on seeds is dominating the previous literature (26.31 %), followed by leaves (10.89 %) and peels (5.75 %). Overall performance analysis showed that plant biocoagulants are superior in removing turbidity (median 83.45 %), while the performance of removing total suspended solids, chemical oxygen demand, and biological oxygen demand are also considerably good (mean 68.38 %, 71.36 %, 67.16 %, respectively). The seeds and other parts of the plants showed the highest removal of turbidity among other parts (mean of removal 90 % and median >90 %). Other parts of the plants are composed mostly of plant extracts, including mucilage (18.47 %), gum (9.67 %), starch (8.36 %), etc. (10.37 %). Overall, the effectiveness of plant biocoagulants in removing pollutants varies compared to that of commercially available coagulants. The current development of biocoagulants indicates that research is currently in the integration and hybridization stage. Future approaches are suggested to focus on upscaling the treatment to an industrial scale, simplifying the extraction procedures, and conducting species-specific analysis to enhance and polish the current knowledge of plant bicocoagulants in water/wastewater treatment.