S/N

Restriction

Causes

Probable solutions

References

1

Requirement of acidic pH (narrow range of operational pH)

• Production of ^ŸOH requires acidic pH (2.5 - 3.5)

• Acidic pH is required to keep Fe²⁺ in soluble form

• pH above 4 promotes complex formation and sludge generation

• Use of heterogeneous catalyst (iron oxide, transition metal, composites, etc.)

• Use of chelating agents such as EDTA, oxalate, etc.

[62] [84] [94]

2

Excessive sludge generation

• Neutralization of the Fenton reaction

• Fluidized-bed Fenton process

• Heterogeneous Fenton

• Electro-Fenton

[69] [72] [95] [96]

3

Chemical consumption/cost of chemicals (H₂O₂)

• Large amount of H₂O₂ may be necessary to completely mineralize pollutants

• Scavenging of H₂O₂ anions/cationspresent

• Use of electro-Fenton/bio-electro-Fenton and other technologies with in situ generation of H₂O₂

• Other alternative_oxidants

[77] [78] [97]