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Coagulation/flocculation is an auspicious procedure for microalgae biomass harvesting. However, the issues of coagulant cost, toxicity, and the large volume of contaminated, nonrecyclable culture medium that is usually generated negate the industrial applications. Therefore, a biocoagulant with frother properties [i.e., the fruit seed extract of Margaritaria discoidea (MDE)] was evaluated as a green biocoagulant to obviate these challenges. The harvesting efficiency (HE %) and the rate parameters were determined in samples collected from a eutrophicated fish pond. The MDE-harvested biomass characteristics were compared with that of the nonchemical approach. Apatococcus lobatus, Arthronema africanum, and Aphanocapsa sp. were the suite of microalgae in the eutrophication system, and the MDE induced the floatation of the microalgae floccule. HE of 98% was achieved and the process obeyed the first-order flotation kinetic. The galactomannans fraction of the MDE flocculated the microalgae cells via the adsorption and bridging mechanism, while the saponin fraction served as the frother that enabled the floatation of the microalgae floccule. The inorganic fraction of the MDE biomass was higher than that of the biomass obtained from the non-chemical method, but the proximate an elemental composition were comparable with the non-chemical method. As shown in the FTIR analysis, no extraneous functional group was introduced into the MDE-harvested biomass. The settleability and filterability of the harvested biomass were comparable with the biomass of other algae species harvested with other types of coagulants.

The need to explicate the mechanisms that underlies the defluoridation of potable water using lateritic soil necessitated this study. Raw laterite sample was thermally treated at varying temperatures that ranged between 100 °C and 1000 °C to determine the effects of thermal treatment on the surficial features and the defluoridation efficiency. The influence of hydrochemistry (i.e., pH, ionic strength, and anionic interference) on the defluoridation efficiency of the lateritic soil was studied. The determination of the effects of thermal treatment on the performance efficiency of the laterites sample showed that the presence of surface hydroxyl group enhanced the defluoridation efficiency. The kinetic analysis of the process showed that the pseudo‐second‐order kinetic equation gave the best description of the process. The evaluation of the influence of ionic strength on the defluoridation efficiency showed that the interaction between the LT0 and the aqua phase F− occurred via inner sphere complex formation. The assessment of the impact of the initial F− solution pH value on the process showed that the possible mode of interaction between the LT0 and the aqua phase F− include electrostatic attraction, ligand exchange, and H‐ bonding. The evaluation of anionic (NO3−, Cl− PO43−, CO32−, and SO42−) interference on the process showed that the mode of interaction between the LT0 and the F− occurred via specific adsorption. Laterite can be effectively used in aqua defluoridation, except where the presence of specific interfering ionic species are abundant. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13107, 2019

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