【環境技術】水中アンモニウムイオンに対して粘土粒子の吸着力は?Spray-Dried Clay Powders for Ammonium Removal

on
Adsorptive Capacity of Spray-Dried pH-treated Bentonite and Kaolin Powders for Ammonium Removal.
Permanent link: https://doi.org/10.1016/j.apt.2021.02.036

A main source of water pollution is run-off from agricultural sites. Agricultural run-off is still considered amongst the most important producers of ammonium pollution. The high concentration of NH4+ in lakes or water streams can cause eutrophication, which results in algal bloom and depletion of dissolved oxygen in water [4]. NH4+ can be toxic and dangerous to health when the concentration in the human body exceeds 200 mg per kg of body weight. The presence of NH4+ in water also causes several other problems, such as creating an odour, forming nitrites in the water supply system, impairing manganese removal, and reducing disinfection efficiency. 肥料が豊富な農地からの流出がアンモニウム(NH4+)汚染の最も重要な発生源の一つであると考えられる。湖や水流における高濃度のNH 4+は富栄養化を引き起こし、藻類の異常発生や水中の溶存酸素の枯渇をもたらす。Novel, cost-effective, and sustainable remediation strategies, such as phytoremediation, are needed to substitute various chemical treating agents towards the removal or detoxification of contaminants.。汚染物質の除去や無害化のために、化学処理剤の代わりには、ファイトレメディエーションのような、コスト効率が高く持続可能な新しい修復戦略が必要である。

Using clay adsorption to support phytoremediation is a promising approach to solve the cost issue. Other advantages of clay (bentonite, kaolinite, etc.) include abundant availability, non-toxicity, high adsorption capacity and large potential for ion exchange, promoting plant growth. フィトレメディエーションを支える粘土吸着の使用は、コスト問題を解決するための有望なアプローチであろう。粘土(ベントナイトやカオリンなど)のその他の利点は、豊富に利用できること、無毒性であること、高い吸着能力、および植物の成長を促進する可能性を含む。

The objective of our study was to evaluate the NH4+ adsorption capability of bentonite and kaolin and their spray-dried powders by adjusting their surface charge under various pH conditions. The zeta potential value of the clays was varied to evaluate their adsorption capacity. The effect of treatment time and clay dosage, as well as the adsorption isotherm were also investigated to better understand the adsorption behavior. 本研究の目的は、種々のpH条件下で表面電荷を調整することにより代表的な粘土系材料であるベントナイトとカオリンを対象にし、霧乾燥法を用いて得られた粉末のNH4+́吸着能力を評価した。

Examination of several physicochemical parameters, such as the surface morphology, surface charge, elemental composition and the crystallinity of the clay particles, was used to validate the efficiency of the treatment.表面形態,表面電荷,元素組成及び粘土粒子の結晶度のようないくつかの物理化学的パラメータの試験を用いて処理の効率を検証した。 Results showed that bentonite adsorption capacity was enhanced by high pH treatment and it was fitted well by the Langmuir isotherm equilibrium model.その結果,ベントナイト吸着容量は高pH処理により増大し, Langmuir等温平衡モデルによく適合した。

課題:水中のアンモニウムイオンの除去

手法:天然粘土(粉末)に処理プロセスを施す

HIGHLIGHTS

For ammonium removal, spray-dried pH-treated clays as adsorbents were prepared.

Adsorption capacity was examined after up to 2 h of sample exposure.

Adsorption isotherm for bentonite showed a fit with Langmuir model.

pH 10-treated (and as-received sample) bentonite showed the highest adsorption capacity.

Abstract

The effectiveness of ammonium (NH4+) adsorption was investigated, using spray-dried, pH-treated bentonite, and kaolin as adsorbents. Each powder’s adsorption capacity towards NH4+ was examined after up to 120 min of sample exposure, and results were compared. The zeta potential values for bentonite samples were between −1.1 and −19.4 mV, while for kaolin samples, they were between −35.7 and −40.9 mV (pH range examined was 2–10). The adsorption isotherm for bentonite showed a fit with the Langmuir model. The pH 10-treated bentonite and as-received bentonite (dispersed as pH 10 in distilled water) showed the highest adsorption capacity towards NH4+. Meanwhile, for kaolin, the adsorption capacity was low and observed only at low NH4+ concentration (100 mg/L and 200 mg/L), with pH 10-treated kaolin showed the highest adsorption capacity. 吸着剤を想定する応用として、噴霧乾燥とpH処理されたベントナイトおよびカオリンを用い、アンモニウム (NH 4+)に対する吸着の有効性を調べた。NH4+に対する各サンプル粉末の吸着容量を120分までの曝露実験後に調べた。ベントナイト試料のゼータ電位値は−1.1から−19.4 mVの間であったが、カオリン試料では−35.7から−40.9 mVの間であった。調べたpH範囲は2から10であった。ベントナイトの吸着等温線はLangmuirモデルと一致した。pH10で処理したベントナイト(及び受け取ったままの)ベントナイト (蒸留水中にpH 10で分散) はNH 4+に対して最も高い吸着容量を示した。一方,カオリンについては吸着容量は低く,低いNH 4+濃度 (100 mg/Lと200 mg/L) でのみ観察されるが、カオリンの場合もpH 10で処理した試料は最も高い吸着容量を示した。

AUTHORS:

Nurul Solehah Mohd Zaini (was a visiting grad. student from UPM), Wuled Lenggoro, Mohd Nazli Naim (TUAT alumnus at UPM), Norihiro Yoshida (Grad. student TUAT), Hasfalina Che Man, Noor Fitrah Abu Bakar, Siti Wahidah Puasa.

INSTITUTIONS

Graduate School of Bio-Applications and Systems Engineering, Department of Applied Physics and Chemical Engineering, and Institute of Global Innovation Research, Tokyo University of Agriculture and Technology (TUAT)

Department of Process and Food Engineering, and Department of Biological and Agricultural Engineering, Faculty of Engineering, Universiti Putra Malaysia

Faculty of Chemical Engineering, Universiti Teknologi MARA, Malaysia

研究室の発表論文の紹介(Introduction of papers from our group) >> https://tag/paper/