Experimental data of adsorption of Cr(III) from aqueous solution using a bentonite: Optimization by response surface methodology

Abstract

Experimental data of adsorption of Cr(III) from aqueous solutions using a Colombian bentonite were acquired. The adsorbent material was characterized by XRF, XRD, and nitrogen physisorption. The effect dataset of pH, agitation speed, contact time and adsorbent amount on the removal of Cr(III) from an aqueous solution, using sodium bentonite was reported. A complete factorial design 32 with two replicates was used to estimate the influence of the adsorbent amount (0.50, 0.75 and 1.00 g) and pH (2.0, 3.0 and 4.0) on Cr(III) removal. Experimental dataset was evaluated with Design Expert® software using the response surface methodology (RSM) in order to obtain the interaction between the processed variables and the response. The optimal conditions for Cr(III) removal from aqueous solution of 50 mg/l were as follows: pH of 3.5, and the bentonite amount equals 0.96 g, keeping constant the contact time at 60 min and stirring speed at 250 rpm. The equilibrium isotherms at 25, 30 and 35 °C were fitted by means of the Langmuir and Freundlich models, and the respective parameters of such models were obtained. The maximum adsorption capacity of sodium bentonite to Cr(III) removal was between 6.44 ± 0.11 and 6.79 ± 0.21 mg/g in the temperature range from 25 to 35 °C. According to the experimental data acquired, sodium bentonite is an effective adsorbent for the Cr(III) removal from aqueous solutions, with the advantage of being a natural, abundant and low-cost material.

Removal of chromate in aqueous solutions by termite nests and reduction chromate accumulation in Brassica chinensis L.

“…At a loading of 10 g/L, the removal efficiencies for C. formosanus and O. formosanus nests reach 87.77% and 98.95%, respectively, with adsorption capacities of 4.39 mg/g and 4.95 mg/g. This trend is attributed to the increased quantity of absorbance, offering more functional groups for adsorption and a larger specific surface area (Castro-Castro et al, 2020). However, removal efficiency plateaus with further loading increase, likely because excessive adsorbent leads to agglomeration, reducing the contact surface area and active adsorption sites (Chen et al, 2020).…”

The Application of the Activated Carbon from Cordia africana Leaves for Adsorption of Chromium (III) from an Aqueous Solution

“…Te Cr (III) removal efciency slightly increased from 63 to 64% as the mixing speed increased from 100 to 300 rpm. Tis might be due to the increase of turbulence in the mixing zone evenly spreading the adsorbents and adsorbates, which will increase the efectiveness of the adsorbent [44]. Te maximum Cr (III) removal efciency (64%) was attained at a mixing speed of 300 rpm.…”

Co-modification of Biochar and Bentonite for Adsorption and Stabilization of Pb2+ ions

“…近年来，随着工业的快速发展与长期的人为活 动，含重金属离子工业废水的不达标排放对水体和 土壤造成了严重污染 [1] ，导致镉大米、血铅超标、 水体砷超标等事件频发。重金属具有持久存留、难 以降解、生物积累的特性 [2] ，严重危害人体健康和 生态安全 [3] 。其中，铅离子 (Pb 2+ )污染得到广泛 关注 [4] 。例如，过量的铅会降低土壤质量和肥力， 进而影响植物的生长和农作物的产量 [5] ；Chen 等 [6] 研究显示斑马鱼的胚胎暴露于低剂量的铅环境，斑 马鱼的行为和学习能力会受到影响。此外，铅中毒 会导致成年人出现脑损伤、精神障碍、高血压以及 肾脏问题 [7] ，并且影响儿童智力和身体发育，造成 注意力和学习能力下降 [8] 。 吸附是一种去除重金属的有效方法，常见的吸 附剂有粘土 [9] 、活性炭 [10] 、石墨烯 [11] 、MOFs 材料 [1 2] 、沸石 [13] 、二氧化硅 [14] 等，这些吸附剂经常被用 于水处理中，但吸附效率仍有待提高 [15] 。生物炭是 一种在缺氧或无氧条件下，经碳化和热化学转化衍 生而来的富碳多孔物质 [16] 。相较于其它吸附剂，生 物炭具有更高的芳香性以及大量官能团 [17] ，能够高 效去除重金属。因此，生物炭以其可再生、来源广 及高效的吸附能力得到广泛关注。 用于制备生物炭的材料来源比较广泛，农业活 动产生的有机废弃物如秸秆、稻草、粪便、木屑、 果壳以及污泥等均可以作为制备生物炭的原料 [18] 。 但在实际应用中，重金属类型、土壤质地、pH、温 度等多种因素都可能会降低生物炭的性能 [19] 。因 此，研究者通过各种改性方法来提高生物炭的实际 应用性能。大量研究表明经过改性的生物炭通常具 有更大的表面积及更高的离子、分子吸附能力 [20] 。 常见的改性方法包括酸/碱改性、金属氧化物改性、 黏土矿物改性 [21] 等。例如，Muhammad 等 [22] 用 Na OH 溶液处理稻米和棉秸秆， 然后将其浸泡在硝酸 F e-Co 溶液或 H3PO4 溶液中，通过慢速热解过程制得 改性生物炭，发现其对 Pb 2+ 和 Cd 2+ 有良好的吸附效 果， 吸附量分别高出原始生物炭的 23%~83%和 17% 556%；Agrafioti 等 [23] 用 CaO 改性浸渍稻壳和城市 固废， 结果表明改性后的生物炭吸附能力显著增强， 对 As 5+ 和 Cr 6+ 的去除率可达 95%；Wang 等 [24] [29] 。被 CaCl2 浸泡后的 CaO-CB 中可以观察到 2θ=37°和 54°的 CaO 的特征峰 [30] ，表明经高温煅 烧后 CaCl2 会脱水为 CaO 并附着在生物炭上。在添 加膨润土的 CaO-Bent-CB 中也可以在 2θ=29°处观 察到膨润土的特征峰 [31] ，表明膨润土与生物炭已混 合均匀。 CB，CaO-CB 和 CaO-Bent-CB 的 FT-IR 光谱如 图 3 所示。在 3415 cm -1 处的强峰与-OH 的拉伸振 动相关， 2920～2850 cm -1 区间内的小峰表明存在脂 肪族的 C-H [32] ， 1701～1370 cm -1 区间的峰表明存在 C=O、芳香族的 C=C [33] 和-COO- [34] ，1130～780 cm -1 区间的峰表明存在 C-O 和芳香族 C-H [35] ，105 6 和 795 cm -1 处的峰分别对应 Si-O 和 Si-O-Si 的伸 缩振动 [36] 。CaO-CB 在 1560～780 cm - Transmittance / (%) [41] 研究粘土生物炭体系的规律类似，即过多的膨润土 会堵塞生物炭孔，造成吸附量下降。 CaO-Bent-CB 吸附等...…”