Humic acid and nano-zeolite NaX as low cost and eco-friendly adsorbents for removal of Pb (II) and Cd (II) from water: characterization, kinetics, isotherms and thermodynamic studies

Abstract

Humic acid as a green-sorbent was synthesized from marine sediments. While kaolin was modified to nano-zeolite NaX. Different tools such as FT-IR, SEM, EDX and XRD were applied to confirm the characteristics of the generated green-sorbents. Different factors such as pH, contact time, sorbent dosage, initial metal ion concentration, temperature and interfering ions were carefully examined and used to optimize the batch adsorption process for Cd2+ and Pb2+. A small dose of nano-zeolite of 100 mg was required to attain the maximum adsorption of Pb2+ at pH about 7, shacking time at 60 min and Pb2+ concentration at 30 ppm. Also, the maximum sorption capacity of Cd2+ ions on nano-zeolite was achieved in a neutral medium and very short contact time implying the economic feasibility of the adsorption process. In the case of humic acid, the maximum removal capacity for Pb2+ and Cd2+ was operated at acidic medium and shacking time was 40 min. Metal ions remediation results were evaluated by some adsorption isotherm models at different temperatures. The kinetic and thermodynamic variables were also computed. The data fitted very well with the linear Langmuir and the pseudo-second-order model implying a favourable adsorption process. The sorption of Cd2+ and Pb2+ was regulated by both external mass transfer and intraparticle diffusion steps over the whole range of concentrations, as shown by the results. The metal ions removal percentage from four real water samples by green sorbents were applied and provides good evidence of two sorbents as promising eco-sorbent for removal of heavy metal ions.

Green synthesis of nanostructured zinc oxide by Ocimum tenuiflorum extract: characterization, adsorption modeling, cytotoxic screening, and metal ions adsorption applications

“…Due to the rapid and growing industrialization which increases the mass of annual discharge of metal ions to the water systems, there is a continuous need for developing methods for treating water from such contaminants. Various adsorption substances are efficient in capturing heavy metals from solutions such as humic acid, zeolite [26], and chitosan [27]. In consideration of the pertinent applications of ZnO NPs, the current work is our contribution to the green synthesis of ZnO NPs employing plant extract.…”

“…After repeated re-dispersions in deionized water, the precipitate was centrifuged and filtered. Calcination of the obtained precipitate was done in a ceramic crucible at 550 °C for 3 h [15,26]. The yielded yellow powder was dried overnight at 80 °C and stored in airtight bottles for characterization.…”

O uso de compostos zeolíticos como adsorventes para a remoção de metais pesados (Pb, Cu, Cr e Mn): uma revisão

“…Ademais, verificou-se a preferência do material zeolítico pela a adsorção dos cátions de chumbo em relação ao zinco. Masoud et al (2022) Ácido húmico e nano-zeólitas NaX como adsorventes de baixo custo e ecologicamente corretos para a remoção de Pb (II) e Cd (II) da água: caracterização, cinética, isotermas e estudo termodinâmico.…”

“…Assim, o pH ideal encontrado para a remoção de Pb 2+ na pesquisa realizada é em geral neutro ou ácido, atuando entre as faixas de pH inferiores a 7,0 (Barsi et al, 2017;Fidelis et al, 2018;Galindo & Huamán, 2022;Masoud et al, 2022).…”

“…Os artigos encontrados apresentaram em sua grande maioria dados experimentais que se adequaram melhor ao modelo de isoterma de Langmuir, a qual como já discorrido, descreve uma adsorção homogênea de sistemas sólido-líquido com a formação de uma monocamada de adsorvato na superfície do adsorvente. Todavia, também se verificou a existência de trabalhos como o de El-Maksod et al (2017), Rahimi e Mahmoudi (2017), Kragovic et al (2018) e Masoud et al (2022) em que o modelo de Freundlich melhor se ajustou aos dados experimentais, o qual descreve uma adsorção de soluções aquosas com a formação de multicamadas sobre o adsorvente e heterogeneidade em sua superfície. Esses estudos diferenciam-se da maioria, em razão da utilização de soluções com baixas concentrações do metal, pois os modelos matemáticos de adsorção linear, tal como a isoterma de Langmuir, não se adequam da melhor forma a condição supracitada, diferentemente do modelo empírico de Freundlich, o qual mesmo a baixa concentrações não reduz sua equação à expressão de adsorção linear.…”