Abstract

Black sand from coastal deposits composed by a mixture containing oxides (Fe₂O₃, TiO₂, SiO₂, ZrO₂, MnO, Al₂O₃, etc.) and metals (V, Cr, Ni, Sr, Ce, etc.). Both this mineral, as well as a fraction obtained from it, have been used as a photocatalyst for hydrogen production from EDTA (electron donor agent) solutions under UV/Vis irradiation. The physical, chemical and optical properties of materials were studied by X-ray fluorescence, scanning electron microscopy/energy-dispersive X-Ray analysis, BET area, thermal gravimetric analysis, X-ray diffraction patterns, Fourier transform infrared and UV–Vis spectroscopy techniques. The effect of several variables, such as chemical composition (Fe/Ti atomic ratio), catalyst dosage, initial pH of suspension, and sacrificial agent (EDTA) concentration on photocatalytic hydrogen production using these minerals were evaluated. The hydrogen production rate was favored by the high content of iron and low initial pH. Catalyst dosage and sacrificial agent concentration show a synergistic effect due to free radicals generated by the photocatalytic mechanism and the turbidity of the suspension (optical depth). In acidic conditions, M1 fraction produced 35,459.78 µmol g⁻¹ (0.5 g l⁻¹ catalyst and 10 mM EDTA), while lowest hydrogen production (350.294 µmol g⁻¹) was obtained using the same sacrificial agent concentration but employing 0.1 g l⁻¹ of M1 at natural pH suspension (pH 4.8). The results are promising since the hydrogen levels produced by this natural ore are close to yields obtained under similar conditions, using synthetized semiconductors. It’s highlight, that in this study a natural catalyst (principle of the geocatalysis), that not was substantially modified.

Graphic Abstract

中文翻译：

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黑砂基光催化剂，用于紫外线可见辐射下的EDTA溶液制氢

摘要

来自沿海沉积物的黑砂，其由含氧化物（Fe ₂ O ₃，TiO ₂，SiO ₂，ZrO ₂，MnO，Al ₂ O ₃的混合物组成）组成等）和金属（V，Cr，Ni，Sr，Ce等）。该矿物以及从矿物中获得的馏分均已用作光催化剂，用于在UV / Vis照射下由EDTA（电子供体试剂）溶液制氢。通过X射线荧光，扫描电子显微镜/能量色散X射线分析，BET面积，热重量分析，X射线衍射图，傅里叶变换红外和UV-Vis光谱研究了材料的物理，化学和光学性质技术。评估了多种变量，例如化学成分（Fe / Ti原子比），催化剂用量，悬浮液的初始pH值和牺牲剂（EDTA）浓度对使用这些矿物的光催化制氢的影响。高铁含量和低初始pH值有利于制氢速度。由于光催化机理产生的自由基和悬浮液的浊度（光学深度），催化剂剂量和牺牲剂浓度表现出协同效应。在酸性条件下，M1馏分产生35,459.78 µmol g^-1（0.5 g l ^-1催化剂和10 mM EDTA），同时使用相同的牺牲剂浓度，但在自然pH悬浮液（pH 4.8）下使用0.1 g l ^-1的M1可获得最低的产氢量（350.294 µmol g ^-1）。结果是有希望的，因为这种天然矿石产生的氢含量接近于使用合成半导体在相似条件下获得的产率。值得一提的是，在这项研究中，天然催化剂（地球催化原理）并未进行实质性修改。

图形摘要