Manganese has recently been a topic of interest among researchers, particularly when 1,752 million tonnes of manganese are expected to be produced by the steel industry in 2020. Manganese discharges from industrial effluents have increased manganese contamination in water sources. Its concentrations of more than 0.2 mg/L in the water sources could have negative impacts on human health and the aquatic ecosystem. Thereby, the available water treatment processes face challenges in effectively removing manganese at low cost. In response to these challenges, adsorption has emerged as one of the most practical water treatment processes for manganese removal. In particular, agricultural waste adsorbents received a lot of attention owing to their low cost and high efficiency (99%) in the removal of manganese. Therefore, this paper reviews the removal of manganese by adsorption process using agricultural waste adsorbents. The factors affecting the adsorption process, the mechanisms, and the performances of the adsorbents are elucidated in detail.

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Manganese (Mn) is one of the most serious pollutants that have negative effects on the ecosystem and water supply. The water industry faces major challenges in its treatment for contaminant and in developing an alternative product with low cost. Among various adsorbents, agriculture waste is preferred due to its biodegradability and availability. The removal of manganese (Mn) from groundwater was investigated using two different adsorbents which are banana blossom peel and floret. SEM analysis shows the formation of microporous structure for both banana blossom peels and floret while FTIR analysis confirms the functional group of strong hydroxyl group that responsible for the adsorption process. The water quality index for the groundwater sample was classified into class III which required extensive treatment. Batch adsorption experiments revealed that both adsorbents had maximum removal efficiency using 0.5 g adsorbent dosage. The banana blossom peel reduces Mn to 0.10 mg/L with 81.1% removal, while the banana blossom floret reduces Mn concentration to 0.12 mg/L with 77.7% removal.

This research aimed to investigate the potential of chemically modified banana blossom peels (BBP) as an adsorbent for removing manganese (Mn) from water. Zeta potential, field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Brunauer–Emmet–Teller (BET) were used to characterise the BBP adsorbent. Batch adsorption studies were used to assess the effects of the solution pH, adsorbent dosage, initial manganese concentration, and contact time of the adsorption process. Zeta potential of BBP with a value of −9.87 to −21.1 mV and FESEM analysis revealed deeper dents and rough internal surfaces conducive to Mn deposition, whereas EDX analysis revealed the presence of C, O, and Na elements (before adsorption); C, O, and Mn (after adsorption). The presence of hydroxyl, carboxylic, and amino groups, which are responsible for the adsorption process, was discovered using FTIR analysis. Furthermore, XRD analysis revealed that the BBP adsorbent structure is amorphous. The BBP adsorbent has a BET surface area of 2.12 m2/g, a total pore volume of 0.0139 cm3/g, and an average pore diameter of 64.35 nm. The BBP adsorbent demonstrated remarkable results of 98% Mn removal under the optimum pH 7, 0.5 g (adsorbent dosage), and 10 mg/L of Mn initial concentration in 150 min of contact time. The linear Langmuir and Freundlich isotherm models best fit the adsorption isotherm data with the R2 > 0.98. In contrast, the adsorption process occurs as a function of the chemisorption as determined by linear pseudo-second-order kinetics. Using 0.1 M HCI, the maximal desorption rate of Mn was 92% in the first cycle, with a recovery rate of 94.18% Mn removal in 30 min. These findings support the use of BBP as a natural adsorbent for Mn removal as a treatment option for improving wastewater quality.

The current study determined the potential of chemical modified banana blossom peels (BBP) as an adsorbent for the removal of manganese (Mn) from water. The BBP adsorbent was characterized using Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) and Brunauer-Emmet Teller (BET). The effects of the solution pH, adsorbent dosage, initial manganese concentration and contact time towards the adsorption process were evaluated in batch adsorption studies. FESEM analysis displayed a deeper dents and rough internal surface that cater for deposition of Mn, while EDX analysis detected the presence of C, O, and Na elements (before adsorption); C, O and Mn (after adsorption). FTIR analysis revealed presence hydroxyl, carboxylic and amino groups which are responsible for the adsorption process. Moreover, XRD analysis showed that the structure of the BBP adsorbent is amorphous. The BET surface area of BBP adsorbent was 2.12 m2/g with the total pore volume of 0.0139 cm3/g and average pore diameter of 64.35 nm. The BBP adsorbent showed promising results of 98% Mn removal at optimum condition of pH 7, 0.5 g (adsorbent dosage), 10 mg/L of Mn initial concentration in 150 min contact time. Adsorption isotherm data were fitted with linear Langmuir and linear Freundlich model best fit with R2 > 0.98, while the adsorption process take place as a function of chemisorption process as determined using linear pseudo-second order kinetics. The maximum desorption rate of Mn was achieved at 92% in the first cycle with recovery rate of 94.18% Mn removal within 30 min using 0.1 M HCl. These findings confirmed the potential BBP as a natural adsorbent for Mn removal as an effective treatment option for enhancing wastewater quality.