The first technique is called phytoextraction wherein plants are used to accumulate the contaminants from the soil before translocating (transfer) the contamination in the aboveground biomass such as shoots (stems and leaves) (Sękara et al., 2005; Rafati et al., 2011; Jacob et al., 2018) and is dubbed as the most important phytoremediation technique in reclaiming contaminants from the polluted soil (Ali et al., 2013; Sarwar et al., 2017) and can be suitable for commercial usage too (Yan et al., 2020). 

    The second technique is called phytostabilization with certain plants species are used to stabilize contaminants in the contaminated soils as to reduce the mobility and bioavailability of pollutants in the environment which will then prevent them from migrating into the ecosystem and entering the food chain (Wong, 2003; Erakhrumen, 2007). The plants will immobilize the contaminants in the soils by sorption using roots in the rhizosphere (Barceló and Poschenrieder, 2003; Wuana and Okieimen, 2011). Even though this technique limits the contaminant accumulation in the biota and minimize leaching into the underground waters, it is still not a permanent solution for remediating the soil as the pollutants remain inside the soil since the movements are limited (Sarwar et al., 2017) thus the phytostabilization technique is suitable as the management strategy to stabilize any pollutants (Vangronsveld et al., 2009). 

      The third technique is called phytovolatilization where the plants will intake pollutants from the soil and converted into volatile form which will become less toxic before being subsequently release into the atmosphere through the process of plant transpiration via the leaves or the foliage systems (Sarwar et al., 2017; Yan et al., 2020). However, similar to phytostabilization, its usage is often limited due to the pollutant that unable to be removed completely from the area and instead is transfer from one segment into another to redeposit it thus making this technique as the most controversial one compared to other phytoremediation techniques (Padmavathiamma & Li, 2007). 

    The fourth and last technique is phytofiltration being the method of removing pollutants from the contaminated surface waters or wastewaters using plants with three different methods of filtration either by plant roots (rhizofiltration), shoots (caulofiltration), or seedlings (blastofiltration) (Mesjasz-Przybyłowicz et al., 2004). During the phytofiltration process, the contaminants will undergo two movements whether it be absorbed by the plants or adsorbed (attached) onto the plants thus minimizing their movements towards underground water (Sarwar et al., 2017). Most of the plants which utilize this technique needed to be hydroponically grown in clean waters as to develop a large root system before substituting the clean water with polluted water for acclimatization and lastly transferred to the contaminated site to remediate the contaminants whereby the saturated parts need to be harvested and dispose appropriately (Yan et al., 2020).