Department of Chemistry, Koneru Lakshmaiah Education Foundation, Green Fields, Vaddeswaram, Andhra Pradesh, India.
Department of Chemistry, RGUKT, Nuzvid, Andhra Pradesh, India.
Int J Phytoremediation. 2023;25(9):1127-1141. doi: 10.1080/15226514.2022.2137101. Epub 2022 Oct 27.
Cadmium is one of the most toxic heavy metal ions found in wastewaters and its remedial methods are globally investigated. Removal methods based on biomaterials as adsorbents are proving to be simple, effective and eco-friendly. In the present investigation, bio-adsorbents derived from plant stems (CRSP) and its active carbon (CRAC) are observed to have good adsorption for toxic cadmium ions. Hence, extraction conditions are optimized for maximum Cd-extraction: 55.0% with 'CRSP' and 70.0% with 'CRAC', from Cd solutions of concentration: 25.0 mg/L. The adsorption capacities are 6.9 mg/g with CRSP and 12.6 mg/g with 'CRAC'. When 'CRAC' is impregnated with nano-CeO (CRAC.nCeO) and is used as adsorbent, the percentage of Cd-extraction is increased to 90.0% and adsorption capacity to 22.5 mg/g at the optimized extraction conditions. To overcome the agglomeration of nanoparticles, the 'CRAC.nCeO' is immobilized in Zr-alginate beads and thus obtained beads are investigated as adsorbent. With beads (CRAC.nCeO-Zr.alg), the percentage of Cd-adsorption is enhanced to 95.0% and adsorption capacity to 24.6 mg/g. The adsorbents are characterized by adopting XRD and FTIR techniques. The adsorption mechanism is assessed by evaluating thermodynamic parameters, isotherm and kinetic models. The thermodynamic parameters and FTIR spectral characteristics indicate the formation of 'surface complex' between Cd and adsorbent's functional groups. The adsorption follows Freundlich isotherm and pseudo-second order model. Many co-ions have not effected the percentage of extraction and interestingly, the presence of some cations (Al and Fe) have synergistically enhanced the Cd-extraction. Spent sorbents can be regenerated and reused with marginal loss of adsorption capacity. The adsorbents developed are successfully used to treat real Cd-polluted wastewater. The novelty of the present investigation is that the effective, eco-friendly, renewable and robust sorbents with high sorption capacities are developed for Cd-remediation of water.
镉是废水中发现的最有毒的重金属离子之一，其修复方法在全球范围内得到了研究。基于生物材料作为吸附剂的去除方法被证明是简单、有效和环保的。在本研究中，观察到从植物茎（CRSP）和其活性炭（CRAC）衍生的生物吸附剂对有毒镉离子具有良好的吸附能力。因此，优化了提取条件以实现最大的 Cd 提取：在 Cd 浓度为 25.0mg/L 的溶液中，用“CRSP”提取 55.0%，用“CRAC”提取 70.0%。CRSP 的吸附容量为 6.9mg/g，“CRAC”的吸附容量为 12.6mg/g。当“CRAC”浸渍纳米 CeO（CRAC.nCeO）并用做吸附剂时，在优化的提取条件下，Cd 的提取率提高到 90.0%，吸附容量提高到 22.5mg/g。为了克服纳米颗粒的团聚，将“CRAC.nCeO”固定在 Zr-藻酸盐珠中，并将得到的珠用作吸附剂。用珠（CRAC.nCeO-Zr.alg），Cd 的吸附率提高到 95.0%，吸附容量提高到 24.6mg/g。采用 XRD 和 FTIR 技术对吸附剂进行了表征。通过评估热力学参数、等温线和动力学模型来评估吸附机理。热力学参数和 FTIR 谱特征表明 Cd 与吸附剂官能团之间形成了“表面配合物”。吸附符合 Freundlich 等温线和拟二级动力学模型。许多共离子没有影响提取率，有趣的是，一些阳离子（Al 和 Fe）的存在协同增强了 Cd 的提取。用过的吸附剂可以再生并重复使用，而吸附容量损失很小。所开发的吸附剂成功地用于处理实际的 Cd 污染废水。本研究的新颖之处在于开发了有效、环保、可再生和稳健的吸附剂，具有高吸附容量，用于水中的 Cd 修复。
