Heterogeneous photocatalytic degradation of picloram, dicamba, and floumeturon in aqueous suspensions of titanium dioxide

Heterogeneous photocatalytic degradation of three-selected herbicide derivatives: (1) picloram (4-Amino-3,5,6-trichloropyridine-2-carboxylic acid, (2) dicamba (2-Methoxy-3,6-dichlorobenzoic acid, and (3) floumeturon (N,N-Dimethyl-N-[3-(trifluoromethyl)phenyl]-urea) has been investigated in aqueous suspensions of titanium dioxide under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic technique and decrease in total organic carbon (TOC) content as a function of irradiation time under a variety of conditions. The degradation of the herbicide was studied under different conditions such as pH, catalyst concentration, substrate concentration, different types of TiO2, and in the presence of electron acceptors such as hydrogen peroxide (H2O2), potassium bromate (KBrO3), and ammonium persulphate (NH4)2S2O8 besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts in the case of dicamba (2) and floumeturon (3), whereas Hombikat UV100 was found to be better for the degradation of picloram (1). The herbicide picloram (1) was found to degrade faster as compared to dicamba (2) and floumeturon (3). The degradation products were analyzed by gas chromatography-mass spectrometry (GC/MS) technique, and plausible mechanisms for the formation of products have been proposed.     

Residual effects of tobacco biochar along with different fixing agents on stabilization of trace elements in multi-metal contaminated soils

The residual effect of tobacco biochar(TB ≥ 500°C) mono and co-application with Cahydroxide(CH),Ca-bentonite(CB) and natural zeolite(NZ) on the bio-availability of trace elements TE(s) in alkaline soils has not been deeply studied yet.A pot study that had earlier been investigated TB mono and blended with CH,CB and NZ on the immobilization of Pb,Cu Cd,and Zn by Chinese cabbage.Maize crop in the rotation was selected as test plant to assess the residual impact of amendments on stabilization of Pb,Cu Cd,and Zn in mine polluted(M-P),smelter heavily and low polluted(S-HP and S-LP,respectively) soils.The obtained results showed that stabilization of Pb,Cd,Cu and Zn reached 63.84% with TB + CB,61.19% with TB + CH,83.31% with TB + CH and 35.27% with TB + CH for M-P soil,36.46% with TB + NZ,38.46% with TB + NZ,19.40% with TB + CH and 62.43% with TB + CH for S-LP soil,52.94% TB + NZ,57.65% with TB + NZ,52.94% with TB + NZ,and 28.44% with TB + CH for S-LP soil.Conversely,TB + CH and TB alone had mobilized Pb and Zn up to19.29% and 34.96% in M-P soil.The mobility of Zn reached 8.38% with TB + CB and 66.03%with TB for S-HP and S-LP soils.The uptake and accumulation of Pb,Cd,Cu and Zn in shoot and root were reduced in three polluted soils.Overall,the combination of TB along with CH,CB and NZ has been proven to be effective in Pb,Cd,Cu and Zn polluted mine/smelter soils restoration.     

Simultaneous removal of Congo red and cadmium(II) from aqueous solutions using graphene oxide–silica composite as a multifunctional adsorbent

Graphene oxide is a very high capacity adsorbent due to its functional groups and π?π interactions with other compounds. Adsorption capacity of graphene oxide, however, can be further enhanced by having synergistic effects through the use of mixed-matrix composite. In this study, silica-decorated graphene oxide (SGO) was used as a high-efficiency adsorbent to remove Congo red (CR) and Cadmium (II) from aqueous solutions. The effects of solution initial concentration (20 to 120 mg/l), solution pH (pH 2 to 7), adsorption duration (0 to 140 min) and temperature (298 to 323 K) were measured in order to optimize the adsorption conditions using the SGO adsorbent. Morphological analysis indicated that the silica nanoparticles could be dispersed uniformly on the graphene oxide surfaces. The maximum capacities of adsorbent for effective removal of Cd (II) and CR were 43.45 and 333.33 mg/g based on Freundlich and Langmuir isotherms, respectively. Langmuir and Freundlich isotherms displayed the highest values of Q_max for CR and Cd (II) adsorption in this study, which indicated monolayer adsorption of CR and multilayer adsorption of Cd (II) onto the SGO, respectively. Thermodynamic study showed that the enthalpy (ΔH) and Gibbs free energy(ΔG) values of the adsorption process for both pollutants were negative, suggesting that the process was spontaneous and exothermic in nature. This study showed active sites of SGO (π-π, hydroxyl, carboxyl, ketone, silane-based functional groups) contributed to an enormous enhancement in simultaneous removal of CR and Cd (II) from an aqueous solution, Therefore, SGO can be considered as a promising adsorbent for future water pollution control and removal of hazardous materials from aqueous solutions.     

Heterogeneous photocatalysed reaction of three selected pesticide derivatives, propham, propachlor and tebuthiuron in aqueous suspensions of titanium dioxide

Heterogeneous photocatalysed reaction of three selected pesticide derivatives such as propham (1), propachlor (2) and tebuthiuron (3) has been investigated in aqueous suspensions of titanium dioxide by monitoring the change in substrate concentration employing UV Spectroscopic analysis and depletion in Total Organic Carbon (TOC) content as a function of irradiation time. The degradation kinetics was studied under different conditions such as pH, catalyst concentration, substrate concentration, different types of TiO(2) and in the presence of electron acceptors such as hydrogen peroxide (H(2)O(2)), potassium bromate (KBrO(3)) and ammonium persulphate (NH(4))(2)S(2)O(8) besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts. The pesticide derivative propham (1) was found to degrade faster as compared to propachlor (2) and tebuthiuron (3). An attempt has also been made to identify the products formed during the photooxidation process through GC/MS analysis technique. All the model pollutants showed the formation of several intermediate products, which were identified on the basis of molecular ion and mass spectrometric fragmentation pattern. A probable mechanism for the formation of the products has been proposed.     

Photocatalysis: an effective tool for photodegradation of dyes—a review

Environmental Science and Pollution Research - The disposal of dye-contaminated wastewater is a major concern around the world for which a variety of techniques are used for its treatment. The...