Determination of minimal duration necessary for the isolation of humic acid contained in composted pineapple leaves

Abstract

--Introduction. The isolation of humic acid (Ha) from decomposed organic substances such as compost is time-consuming, as it takes not less than 24 h. We investigated whether the isolation time of Ha produced from composted pineapple leaves could be reduced. Materials and methods. Ha from 10 g of pineapple compost was extracted with 100 mL of 0.10 M NaOH. Different extraction times [(4, 8, 12, 16, 20 and 24) h] were tested. At the end of each time, the samples were centrifuged. The dark-colored supernatant liquor containing Ha was decanted and filtered; the pH of the solution was adjusted to 1.0. After acidification, the fractionation times tested were (3, 6, 9, 12, 15, 18, 21 and 24) h. At the end of each fractionation time, the supernatant liquor (fulvic acid) was siphoned off from the acidified extract. The remainder of the suspension was transferred to a polyethylene bottle. Ha was purified by suspending it in 50 mL distilled water, then centrifuged, and the supernatant was decanted. After repeating this procedure five times, the supernatant and the fulvic acid were analyzed for Ca, K, Mg, Mn, Na, Cu, Fe and Zn. The washed Ha was oven dried at 30°C to a constant weight and the Ha samples were analyzed for ash and mineral matter. Results and discussion. The ash content was not more than 1%, the generally acceptable maximum value. The mineral contents decreased in Ha samples with washing. The yield of Ha significantly increased with increasing extraction time, except for the (20 and 24) h extraction times, which did not show statistically different Ha yield, meaning that the exchange sites of Ha of the pineapple compost might have been saturated with Na ions from 20 h. There was no significant difference among the fractionation times, indicating that Ha of the pineapple compost requires about 3 h to equilibrate or stand immediately after acidification for the H ions to replace the Na and the other cations. There was no significant interaction between the factors extraction and fractionation. Conclusion. The isolation of humic acids from composted pineapple leaves can be achieved with an extraction time of 20 h and a fractionation time of 3 h. Malaysia / Ananas comosus / waste utilization / composting / composts / humic acids / methodsDétermination du temps minimal nécessaire à l'isolement de l'acide humique contenu dans du compost de feuilles d'ananas.

Simple and Rapid Method of Isolating Humic Acids from Tropical Peat Soils (Saprists)

“…It must, however, be pointed out that where the characterization of the HA is of primary importance instead of the amount of HA isolated, an optimum yield (16.54%) of HA equivalent to optimum extraction period of 4 h or less could be considered, as the longer the extraction period, the greater will be the chemical changes. Optimum yield was calculated as 90% of the maximum yield of HA corresponding to maximum extraction period of 24 h beyond which this yield will not be time wise economical [9,10] . No significant relationship between the period of fractionation with yield of HA suggests that the yield of HA was not affected by fractionation period.…”

“…The HA extraction was conducted using the procedures described by other authors [9,10,11] with some modifications. Five gram (dry weight basis) peat soil samples at natural moisture content were placed into polyethylene centrifuge bottles (250 mL) and 50 mL 0.1 M NaOH solution was added and the bottles stoppered tightly with rubber stoppers.…”

“…Fractionation period ranges between 12 and 24 h [4,6] , although most studies usually use 24 h [6][7][8] . It must be emphasized that where the state of the art technologies are not available or expensive to afford, particularly in developing countries, it usually takes between 2 to 7 days to purify (removal of mineral matter like ash) HA Our recent studies have shown that the purification period of HA from composted pineapple leaves could be reduced from 7 days to between 1 and 2 h [9,10] but an information such as this is lacking for HA of well decomposed peat soils (Saprists). In another study, we managed to reduce extraction and fractionation periods of HA in compost from 48 to 17 h and 24 to 3 h, respectively [9] .…”

“…It must be emphasized that where the state of the art technologies are not available or expensive to afford, particularly in developing countries, it usually takes between 2 to 7 days to purify (removal of mineral matter like ash) HA Our recent studies have shown that the purification period of HA from composted pineapple leaves could be reduced from 7 days to between 1 and 2 h [9,10] but an information such as this is lacking for HA of well decomposed peat soils (Saprists). In another study, we managed to reduce extraction and fractionation periods of HA in compost from 48 to 17 h and 24 to 3 h, respectively [9] . These relationships are important because they enable the calculation of the maximum and optimum yields of HA with extraction or fractionation or both procedures, an information lacking for HA of Saprists.…”

Effect of Enhancing Urea-Humic Acid Mixture with Refined Acid Sulphate Soil

“…The soil was air dried, meshed and sieved to pass a 2 mm sieve before it was characterized for selected soil chemical properties such as pH using glass electrode [6] , Cation Exchange Capacity (CEC) by leaching using 1 N ammonium acetate (adjusted to pH 7) followed by steam distillation technique [7] , exchangeable cations (K, Ca, Mg, Na and Fe) by the double acid method and atomic absorption spectrophotometry (A Analyst 800, Perkin Elmer Instruments, Norwalk, CT) [8] . The HA was isolated from a tropical peat (hemist) soil at 0-25 cm depth using the method described by Susilawati et al [9,10] . The oven dried yield of HA was expressed as percentage of the weight of soil used.…”