Photodegradation mechanism of two dyes: the influence of adsorption behavior on the novel TiO_2 particles

The relationship between adsorption behavior and photocatalytic mechanism of the two dyes was investigated. Adsorption isotherms showed that the adsorption of cationic pink FG was Langmuir type behavior, while the reactive brilliant red k-2G was Freundlich type behavior. The increasing pH favored the adsorption of FG but have little effect on the photodegradation. The increasing pH favored the adsorption and the photodegradation of k-2G. The presence of scavenger of h + vb and OH· radical potassium iodide inhibited the degradation of k-2G, free radicals scavenger tetranitromethane inhibited the photodegradation of FG. These results indicated that the photodegradation of FG mainly via free radicals in solution, and the photodegradation of k-2G was mainly on the catalysts surface or near the interface of solid and solution by react with h + vb and surface-bound OH·. The different effect of SO 2- 4, HCO - 3 on the adsorp tion and photodegradation of two dyes confirmed these results.

Quantum chemical investigation on photodegradation mechanisms of sulfamethoxypyridazine with dissolved inorganic matter and hydroxyl radical

Sulfamethoxypyridazine（SMP） is one of the commonly used sulfonamide antibiotics（SAs）.SAs are mainly studied to undergo triplet-sensitized photodegradation in water under natural sunlight with other coexisting aquatic environmental organic pollutants.In this work,SMP was selected as a representative of SAs.We studied the mechanisms of triplet-sensitized photodegradation of SMP and the influence of selected dissolved inorganic matter,i.e.,anions（Br^-,Cl^-,and NO^-_3） and cations ions（Ca^（2＋）,Mg^（2＋）,and Zn^（2＋）） on SMP photodegradation mechanism by quantum chemical methods.In addition,the degradation mechanisms of SMP by hydroxyl radical（OH·） were also investigated.The creation of SO_2 extrusion product was accessed with two different energy pathways（pathway-1 and pathway-2） by following two steps（step-I and step-II） in the tripletsensitized photodegradation of SMP.Due to low activation energy,the pathway-1 was considered as the main pathway to obtain SO_2 extrusion product.Step-II of pathway-1 was measured to be the rate-limiting step（RLS） of SMP photodegradation mechanism and the effect of the selected anions and cations was estimated for this step.All selected anions and cations promoted photodegradation of SMP by dropping the activation energy of pathway-1.The estimated low activation energies of different degradation pathways of SMP with OH·radical indicate that OH·radical is a very powerful oxidizing agent for SMP degradation via attack through benzene derivative and pyridazine derivative ring.

Construction of immobilized films photocatalysts with CdS clusters decorated by metal Cd and BiOCl for photocatalytic degradation of tetracycline antibiotics

A kind of CdS/Cd-BiOCl immobilized films photocatalyst was prepared.The optical and physicochemical properties of the CdS/Cd-BiOCl photocatalysts were analysed,and the detailed characterization revealed CdS/Cd-BiOCl films photocatalyst with good charge carrier separation effect.The reusabilities and photocatalytic properties of the samples were studied.The 15%Cd S/Cd-Bi OCl photocatalyst exhibited superior performance in photocatalytic degradation of tetracycline(TC)and favorable stability under visible light irradiation.As for the photodegradation rate of TC,15%CdS/Cd-BiOCl exhibited an excellent photodegradation activity,which is 4.06 and 9.53 times higher than that of Cd S/Cd and Bi OCl,respectively.The results showed that dominant active species are·O_(2)^(-)and·OH radicals during photodegradation.The charge transfer in Z-scheme CdS/Cd-BiOCl films photocatalyst could synchronously generate conduct band(CB)electrons in BiOCl and valence band(VB)holes in CdS,and metal Cd served as electron mediator.This work can be a reference for the design of film photocatalysts and new insight for photodegradating towards contaminants.