School of Environmental Science and Engineering, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, 721302, India.
Department of Earth and Environmental Studies, National Institute of Technology Durgapur, Durgapur, West Bengal, 713209, India.
Environ Sci Pollut Res Int. 2022 Mar;29(14):20017-20034. doi: 10.1007/s11356-020-12158-0. Epub 2021 Jan 4.
Adsorptive removal of copper by activated carbon derived from modified rice husk (ACRH) was studied in the presence and absence of magnetic field (MF). The ACRH was prepared from the normal rice husk treated by NaOH solution and subsequent pyrolysis at 450 °C in the absence of oxygen. The physicochemical properties of ACRH's were determined before and after the adsorption process to delineate the adsorption mechanism. The BET analysis confirmed that the fabricated ACRH has a specific surface area of 8.244 m/g with a mesopore to micropore ratio of 0.974. It was observed that the micropore structure gradually replaced the mesopores, and the surface area of the micropore increased (from 0.9219 to 4.1764 m/g), and the pore diameter was also decreased from 180.381 to 46.249 Å after pyrolysis. The CHNO/S test result reveals that the carbon content was increased from 42 to 67.8% in the ACRH after pyrolysis. The batch sorption studies were performed by varying the initial adsorbate concentration, temperature, agitation speed, pH, adsorbent dose and contact time for magnetic and non-magnetic conditions to analyze the effect of the magnetic field. The univariate studies show that the maximum experimental adsorption capacity was 4.522 mg/g and 3.855 mg/g, respectively, for these two conditions (representing the magnetic impact) at 25 °C with an adsorbent dose of 2 g/L and an agitation speed of 150 rpm. It was also observed that the removal efficiency was 94.55% and 77.96% (magnetic and non-magnetic condition) at pH 7 with a concentration of 10 mg/L in 2 h. The test result on the impact of exposure time on the magnetic field suggested that the magnetic memory influenced the removal efficiency; after 40 to 60 min, the maximum removal efficiency was achieved, around 80 to 90%. The pseudo-second-order kinetic model was best fitted with the experimental data with a rate constant as 0.1749 and 0.1006 g/mg/min for these two conditions. The Temkin model delineates the adsorption isotherm suggesting the heat generated during the adsorption process is linearly abate with the coverage of the surface area of the adsorbent. The thermodynamic model confirms that the copper adsorption is spontaneous (ΔG = - 3.91 kJ/mol and - 6.02 kJ/mol), wherein the negative enthalpy value (ΔH = - 36.74 kJ/mol and - 25.74 kJ/mol) suggested that the process is exothermic irrespective of magnetic interference. The significant enhancement of copper removal was observed by incorporating the magnetic field, showing an increase in sorption capacity by 17.48% and a reduction of reaction time by 88.12%.
在存在和不存在磁场的情况下，研究了用改性稻壳（ACRH）制备的活性炭对铜的吸附去除作用。ACRH 是由用 NaOH 溶液处理的普通稻壳和随后在无氧条件下在 450°C 下热解制备的。在吸附过程前后测定了 ACRH 的物理化学性质，以阐明吸附机理。BET 分析证实，所制备的 ACRH 的比表面积为 8.244 m/g，中孔与微孔的比例为 0.974。观察到微孔结构逐渐取代中孔，并且微孔表面积增加（从 0.9219 增加到 4.1764 m/g），并且孔径也从 180.381 减小到 46.249Å热解后。CHNO/S 测试结果表明，热解后 ACRH 中的碳含量从 42 增加到 67.8%。通过改变初始吸附质浓度、温度、搅拌速度、pH 值、吸附剂剂量和接触时间来进行批吸附研究，以分析磁场的影响。单变量研究表明，在 25°C 下，这两种条件（分别代表磁场的影响）下的最大实验吸附容量分别为 4.522mg/g 和 3.855mg/g，吸附剂剂量为 2g/L，搅拌速度为 150rpm。还观察到在 pH 为 7 时，浓度为 10mg/L 的情况下，去除效率分别为 94.55%和 77.96%（磁场和非磁场条件），在 2 小时内达到。磁场对暴露时间影响的测试结果表明，磁记忆影响了去除效率；在 40 到 60 分钟之间，达到了最大的去除效率，约为 80 到 90%。准二级动力学模型与实验数据拟合最好，这两种情况下的速率常数分别为 0.1749 和 0.1006g/mg/min。Temkin 模型描述了吸附等温线，表明吸附过程中产生的热量随吸附剂表面积的覆盖线性减少。热力学模型证实，铜的吸附是自发的（ΔG=-3.91kJ/mol 和-6.02kJ/mol），其中负焓值（ΔH=-36.74kJ/mol 和-25.74kJ/mol）表明该过程是放热的，与磁场干扰无关。通过引入磁场，可以观察到铜去除率的显著提高，吸附容量提高了 17.48%，反应时间减少了 88.12%。
