[Phosphate Removal Using Rice Husk Biochars Modified with Lanthanum Hydroxide].

La-modified RHBCs (La-RHBCs) were fabricated by immobilizing La(OH)3 nanoparticles on mesoporous rice husk biochars (RHBCs) using a co-precipitation method. Specifically, the effects of the pore structure of the RHBCs, solution pH, and coexisting substances on phosphate adsorption by the La-RHBCs were studied. The results showed that the La loading of the La-RHBCs was positively correlated with the mesoporosity of the RHBCs. La-modified RHBCs with higher mesoporosity hosts showed faster adsorption rates and lower leaching of La during phosphate adsorption. The adsorption process could be described by a pseudo second-order kinetic model, and the reaction rate was controlled by intraparticle diffusion. The Langmuir isotherm model fitted the adsorption process better, and the theoretical maximum adsorption capacities were 41.22, 43.26, and 45.62 mg·g-1, respectively. The high P/La molar ratios of more than 1.5 indicated the high utilization efficiencies of the La in the La-immobilized RHBCs. Moreover, phosphate could be effectively removed by the La-modified RHBCs over a wide pH range of 3-9. The La-modified RHBCs also exhibited good adsorption selectivity towards phosphate in the presence of coexisting anions and humic acids. Phosphate adsorption by the La-RHBCs was enhanced in the presence of Ca2+, while it was inhibited in the presence of Mg2+.

Photocatalytic pretreatment of oily wastewater from the restaurant by a vacuum ultraviolet/TiO2 system.

The present study aims at investigating the performance of a vacuum ultraviolet (VUV, 185 nm) and TiO(2) oxidation system for the pretreatment of oily wastewater from restaurant. The influence of irradiation time, pH, dissolved oxygen (DO), the dosage of TiO(2) and the initial chemical oxygen demand (COD) concentration on COD removal efficiency was ascertained and optimum process conditions for stable and effective operation were determined. Under the optimum conditions of irradiation 10 min, initial COD 3981 mg/L, TiO(2) 150 mg/L, pH 7.0 and flow rate of air 40 L/h, the process of VUV and TiO(2)/VUV achieved removal efficiencies of COD, BOD(5) and oil as 50±3%, 37±2%, 86±3%, and 63±3%, 43±2%, 70±3%, respectively. The biodegradability factor f(B) of the wastewater was determined as 1.56 which indicated that the VUV/TiO(2) process improved the biodegradability of the oily wastewater significantly. Results clearly indicate that VUV/TiO(2) photolysis tends to destruct parts of COD, BOD(5), and ammonia, as well as enhances the biodegradability of the oily wastewater simultaneously. Thus, this technique could be used as a pretreatment step for conventional biological treatment of oily wastewater.

[Removal nitrogen in wavy subsurface-flow constructed wetland utilizing aeration and recirculation].

To improve the removal rates of ammonium nitrogen in the constructed wetlands, the traditional wavy subsurface-flow constructed wetland (W-SFCW) was modified to install the aeration tube in the second wave interval to improve the DO and the nitrification rates within the constructed wetlands. It was found that as most of COD had been removed in the second wave interval, nitrifying bacteria become dominant in the third wave interval, which led to the nitrification extent reaching more than 90%, and the ability to endure the impact of hydraulic loading was enhanced. Recirculation rates of 50% were adopted to evaluate the effect on TN removal. It showed that with effluent recirculation the average removal efficiencies of TN obviously increased to 50% when the wastewater entered 1/3 of the wetland not infall. The hydraulic loading of wetland reached 0.8 m3/(m2 x d), and COD organic loading was 56-112 g/(m2 x d), and the ammonium loading rate was 20-28 g/(m2 x d).