Char-based adsorbents (char-FeCl3, char-FeCl2, and char-FeCit) derived from cotton textile waste (CTW) were synthesized by one-step low-temperature pyrolysis approach with different iron salts. The properties of the samples were conducted by BET, SEM, EDS, XRD, XPS, TEM, and FTIR. The results suggested that the surface areas of char-FeCl3 and char-FeCl2 were higher than those of char-FeCit. The presence of Fe2O3 as well as pyrolysis gas (HCl (g) and H2O (g)) could catalyze the formation of porosity. Meanwhile, FeCl3 showed the strongest catalysis effect to decompose cellulose to produce char. The pyrolysis process analysis was investigated by means of thermogravimetry-DSC. FeCl3 and FeCl2 could accelerate the breakage of cellulose structure whereas FeC6H5O7 was not beneficial to form char at low temperature as the incomplete decomposition of citrate. The adsorption property of Cr(VI) for the chars was evaluated. Adsorption processes were fitted well with the Freundlich model, and char-FeCl3 presented the best adsorptive capacity (70.39 mg/g). Thus, this low-temperature pyrolysis method was economical and technologically simplified as well as efficient adsorption capacity of Cr(VI) removal. Graphical abstract.

中文翻译：

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在低热解温度下，由铁盐辅助的棉纺织废料合成炭基吸附剂，用于去除Cr（VI）。

棉纺织废料（CTW）衍生的碳基吸附剂（char-FeCl3，char-FeCl2和char-FeCit）是采用不同铁盐的一步式低温热解方法合成的。样品的性能通过BET，SEM，EDS，XRD，XPS，TEM和FTIR进行。结果表明，char-FeCl3和char-FeCl2的表面积均大于char-FeCit的表面积。Fe2O3以及热解气体（HCl（g）和H2O（g））的存在可以催化孔隙的形成。同时，FeCl3表现出最强的催化作用，分解纤维素产生炭。借助热重分析-DSC研究了热解过程分析。FeCl3和FeCl2可以加速纤维素结构的破裂，而FeC6H5O7则不利于低温下形成炭，因为柠檬酸盐不完全分解。评价了Cr（VI）对炭的吸附性能。吸附过程与Freundlich模型非常吻合，并且char-FeCl3表现出最佳的吸附能力（70.39 mg / g）。因此，这种低温热解方法在经济和技术上都得到了简化，并且有效去除了Cr（VI）。图形概要。这种低温热解方法在经济和技术上都得到了简化，并且具有有效的吸附能力去除Cr（VI）。图形概要。这种低温热解方法在经济和技术上都得到了简化，并且有效去除了Cr（VI）。图形概要。