Browsing by Author "Paradelo, Marcos"

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Hydroxyapatite-activated seaweed biochar for enhanced remediation of fluoride contaminated soil at various pH ranges.
(Elsevier Ltd., 2022-12-10) Moirana, Ruth; Mkunda, Josephine; Machunda, Revocatus; Paradelo, Marcos; Mtei, Kelvin
This study investigated the defluoridation efficiency of hydroxyapatite-activated seaweed (Eucheuma Cottonii) biochar (HSB) at various soil pH ranges (3–11) while monitoring the impact of contact time (30 min - 2.5 h), adsorbent dosage (0.1–0.5 g) as well as the initial fluoride concentration and compare its performance to its respective seaweed biochar (SB). Activation of SB with the hydroxyapatite lead to a shift in its point-zero-charge (pHPZC) from 6 to 7.4 broadening its defluoridation pH range from a solitary 5 to amid 3 through 11. The fluoride adsorption mechanism was found to follow both Langmuir (R2 = 0.956) and Freundlich (R2 = 0.942) isotherm models with a maximum defluoridation capacity of 3.03 mg/g equivalent to the defluoridation efficiency of 79%. This is accounted to the existence of soil ions, SB active sites, and the attached hydroxyapatite, as fluoride adsorption sites each exhibiting a dissimilar fluoride removal mechanism. Therefore, the HSB could be a promising adsorbent for fluoride removal in the fluoride contaminated agricultural soils of inclusive pH ranges.
Remediation of Soils Contaminated by Fluoride Using a Fermentation Product of Seaweed (Eucheuma cottonii)
(Hindawi, 2022-10-03) Moirana, Ruth; Mkunda, Josephine; Paradelo, Marcos; Machunda, Revocatus; Mtei, Kelvin
is study investigated the e cacy of fermented seaweed (Eucheuma cottonii) on the remediation of uoride-contaminated soil. e soil was amended with either 1.25, 3.0, or 5.0% (w/w) fermented seaweed (FSW), parallel with the controls (0%). e amendment improved the physicochemical properties of the soil particularly pH regulated from strong alkaline (9.3) to neutral (7.0) which is essential for germination, crop growth, and yield. e amount of water soluble- uoride (Ws-F) dropped from 81.7 ± 3.1 mg/kg to 42.7 ± 2.4, 33.7 ± 1.2, 19.6 ± 0.9, and 12 ± 1.3 mg/kg following 0, 1.25, 3, and 5% amendment dosage, re spectively. Most of the Ws-F was converted into exchangeable uoride (Ex-F) and to uoride-bound to iron and manganese (Fe/ Mn-F). Furthermore, the amendment also enhanced microbial mass and diversity in the soil. e FSW contains organic acids which participate in ionic bonding with the multivalent cations in the soil. e formed compound participates in ion exchange with clay or with anionic adsorption to positively charged clay sites at the edges. is interaction is further essential for enhancing the uoride holding capacity of the soil. e use of seaweed reduced the bioavailability of uoride in the agricultural soils and had positive e ects on promoting soil fertility. However, further studies to observe its e ects on crop performance is of signi cance.