Solar Photocatalysis of A Pesticide in A Tubular Reactor on Titaniferous Sand as A New Semi-Conductor

This present study comes in addition to overcome the problems of separation of fine particles of TiO2 in heterogeneous photocatalysis after treatment. It aims to show the potential for using titaniferous sand as a new semiconductor under solar irradiation. The photocatalytic efficiency of this titaniferous sand was tested on a pesticide (Azadirachtin). A tubular photocatalytic reactor with recirculation of the polluting solution was designed for the elimination of the pesticide in an aqueous solution. Before its use as a photocatalyst, the titaniferous sand has undergone a specific treatment that consists of calcination at 600℃ followed by extraction of the calcined natural organic materials, which can interfere with the measurement of analytical parameters such as COD. The titaniferous sand was also characterized by X-ray fluorescence spectroscopy (XRF). XRF analyses have shown that TiO2 is predominant in the titaniferous sand with a percentage that has been estimated at 46.34%. The influence of various experimental parameters such as the flow rate of the polluting solution, the concentration of titaniferous sand, the presence of oxygen and the intensity of the overall rate of sunshine, was studied to optimize the photocatalytic degradation of the pesticide. The results showed that the highest removal rate (70%) was observed under the following conditions: a pH of 6, a titaniferous sand concentration of 150 g/L, a flow rate of 0.3 mL/min, and a sunshine rate of 354 W/m2 and in the presence of atmospheric oxygen. Under these experimental conditions, the rate of photodegradation of the pesticide follows the pseudo first order kinetic model of Langmuir Hinshelwood with a coefficient of determination R2 of 0.9869 and an apparent rate constant of 0.0029 min-1. The results clearly demonstrated the potential of titaniferous sand as a photocatalyst sensitive to sunlight for the effective removal of pesticides in the aquatic environment.

Modelling and Response Surface Optimisation of Methyl Violet Removal by a Mixture of Titaniferous Sand and Non-Activated Attapulgite

In recent years, the discharge of dye-laden effluents from the textile industries into the aquatic environment has increased considerably. These industries are among the largest consumers of water. They generate huge amounts of pollutants from their huge discharge of toxic effluents and pose serious public health problems. So, this study focuses on the use of the mixture of titaniferous sand and attapulgite for the removal of methyl violet by adsorption in discontinuous mode. The different adsorbents were characterized by X-ray fluorescence spectroscopy and their different physico-chemical properties such as pH, zero charge potential, bulk and absolute density, porosity and specific surface area were determined. The response surfaces, through the Box-Behnken model, were used to model and optimize the operating conditions. The different factors studied were the ratio of titaniferous sand and attapulgite, the initial concentration of methyl violet and the pH. These vary between 1.25 and 8, 20 and 100 mg/L, 4 and 10 respectively. The results obtained after statistical analysis of the data show that the optimum mixture ratio is 2, the optimum concentration is 99.92 mg/L and the optimum pH is 9.88 corresponding to a maximum capacity of 5.52 mg/g and a maximum removal efficiency of 99.56%. The study of the effects of the different factors showed that the initial concentration of methyl violet and the pH significantly influence the adsorption capacity and the removal efficiency of the dye.

Modelling and Optimisation of Copper Adsorption in Solution by the Response Surface Method

Copper is considered a heavy metal that can be toxic at certain concentrations and its presence in water is a potential threat to public health. These heavy metals also contribute to a remarkable degradation of the environment, hence the need for effective treatment methods to remove them. In this study, a mixture of titaniferous sand and calcium silicate was used as adsorbent material to eliminate copper in solution. The calcium silicate was synthesised from fluosilicic acid, which is a by-product of phosphoric acid manufacture. The titaniferous sand is a residue from a mining industry. Both adsorbents were characterised by infrared spectroscopy and X-ray fluorescence to determine their compositions and physicochemical properties. The response surfaces, through the Box-Behnken model, were used to model and optimise various adsorption parameters, namely initial copper concentration (A: 60 - 200 mg/L), adsorbent dose (B: 0.1 - 0.6 g) and pH (C: 4 - 10). The copper removal efficiency (98.92%), after statistical analysis, was obtained under the following optimal conditions: an adsorbent dose of 0.55 g, an initial copper concentration of 197.25 mg/L and a pH of 9.85. The study of the effects of the operating parameters showed that they had a positive effect on the copper removal efficiency.

Beneficiation of Titanium Oxides From Ilmenite by Self-Reduction of Coal Bearing Pellets

The study on the beneficiation of titanium oxides from Panzhihua ilmenites by reduction of coal bearing pellets was carried out. The iron oxides in pellets were efficiently reduced to metal iron, and titanium oxide slag beneficiated was separated from metal iron. The effect of temperature, flux and coal blending ratio on the reduction and separation was investigated, and rational parameters were determined. A new process for the beneficiation of titanium oxides by rotary hearth furnace （RHF） was proposed.

Experimental study and industrial demonstration on utilization of Fe,Ti and V from vanadium-bearing titanomagnetite ore sands

In order to achieve highly efficient utilization of three valuable elements Fe,Ti and V simultaneously from vanadium-bearing titanomagnetite ore sands,an improved carbothermic reduction method was proposed and verified in both laboratory scale and industrial test-bed scale.The method combined the process of direct reduction and the process of further reduction and separation.Particularly,pulverized coal injection was introduced.In experimental tests,the effects of parameters such as carbon content in briquette,reduction duration and reduction temperature on the contents of metallic Fe and FeO as well as Fe metallization rate were analyzed.Experimental results indicated that Fe metallization rate in the carbon-containing briquette could reach 75.83%.In the industrial test-bed tests,the effects of carbon content in briquette,reduction duration and reduction temperature were also investigated,respectively.In addition,processes with and without pulverized coal injection were tested.The comparative analysis indicated that the content of TiO2 in titaniferous slag was increased by applying pulverized coal injection,and it can reach 82.5 wt.%.Meanwhile,the energy performance analysis showed that the equivalent electricity consumption of the test-bed dropped significantly to 2071 kWh per ton of slag,about 26.0%less than that of traditional method.Moreover,the investment payback of the test-bed is 3.4 years.Both experiments and industrial test-bed tests demonstrated that the proposed method has the advantages of highly efficient utilization,high energy efficiency as well as good economic performance.