۱- Introduction

۲- Photocatalyst

۳- Adsorbents

۴- Integrated photocatalyst adsorbents (IPCA)

۵- Conclusions and recommendations for future work

References

Abstract

Photocatalysis has the best potential to replace the conventional wastewater treatment technology due to its utilization of visible light to photo-degrade organic and inorganic contaminants. However, when applied in slurry form, agglomeration of nanoparticle will lead to serious decrease in photocatalytic performance due to hinderance effect. By combining the photocatalyst and adsorbents, which is designated as integrated photocatalyst adsorbent (IPCA), an adsorbent material which also degrades toxic organic compounds in the presence of UV/visible light irradiation could be produced. The compound does not only preserve all the interesting characteristics of both individual components, but also overcomes serious drawbacks, such as low absorptivity, rapid recombination of photogenerated electrons and hinderance effect of photocatalyst when applied in slurry form. There are several criteria that must be obeyed by the absorbent material used such as high absorption capacity to target compound, reasonable transparency to UV–vis light, high surface area, inhibition of photocatalyst leaching and good stability with dispersing solvent. In this review article, the authors presented an overview on the application of photocatalyst, adsorbents and integrated photocatalyst adsorbents for wastewater treatment. Moreover, the discussions were also focused on the major adsorbent which has been integrated with photocatalyst such as carbon, clays, zeolite matrix materials and others. Additionally, the mechanisms of the adsorption of emerging organic contaminants with adsorbents in IPCA were also discussed to clearly understand the possible interactions between organic contaminants and IPCA. Outlook on IPCA study were also discussed to further broaden the prospective of this technology.

Introduction

Water is a precious source that is important to every living thing throughout the world. Water covered almost 70 percent on the earth but only 2.5% is indicated as clean water. The minor amount of clean water is used, recycled, and then treated so that it can be repurpose again. Usage of water is not only limited to domestic usage but also in broad areas of application including industrial and agriculture. According to UN WWAP in 2003, about 2 million tons of untreated water originates from industrial and agriculture water runoff. Increased amount of water usage would generate increased amount of wastewater. Wastewater treatment requires high cost because the contaminant present in the wastewater must be removed effectively so that water can be reuse again safely. Even with conventional methods such as biological and physical treatments, to remove the contaminants effectively would still require more advanced technology with lower cost and shorter time requirements [1]. Thus, findings the best practices/ strategies for wastewater management are crucial for our environment and sustainable development. Nowadays, various kind of materials have been employed to remove the contaminants from wastewater, including catalyst (homogenous and heterogenous), adsorbents, membrane from organic and inorganic materials, ozone, etc [2–۷]. The conventional water treatment technologies that are available nowadays such as adsorption or coagulation, does not completely eliminate or destroy the pollutants. Somehow, these pollutants were simply being concentrated by transferring them another phase. Hence, finding an alternative water treatment technology that can completely eliminate or destroy these contaminants is highly sought after. Advanced oxidation processes (AOPs) is a recently discovered wastewater treatment technology which treats pollutants by generating hydroxyl radicals which are responsible for organic degradation. Due to their strong unselective oxidative power, the hydroxyl radicals oxidize and mineralize almost any organic molecule, yielding CO2 and inorganic ions as final products [8].