This study reviewed the use of hydrochars in the adsorption of methylene blue, a toxic dye, from aqueous phases. Journal articles published predominantly between 2020 and 2025 were assessed. The articles were mainly identified through keyword searches on ScienceDirect, Scopus and Web of Science. The studies reported a high efficacy of hydrochars against the dye. Organic wastes were primarily used as a feedstock in the hydrothermal carbonization processes, aligning to the waste to resource principle, an efficient and cost effective route of synthesis of adsorbents. The pseudo-first order, pseudo-second order and the Elovich model best described the kinetic data while the Freundlich, Sips and Langmuir isotherms best fitted the experimental data, with model predicted adsorption capacities in the range of 30-1060 mg g− 1. All the reviewed studies reported a spontaneous and feasible adsorption process (negative ΔG), while the entropy (ΔS) and enthalpy (ΔH) values varied with feedstock used, the specific modification routes and modification conditions. Several systems retained between 65 and 95
This work investigates the effects of hydrochar (HC) derived from Cuscuta (dodder), an invasive plant, on the textural, structural, morphological, and porosity properties, as well as the adsorptive performance of pozzolan-based alkali-activated geopolymers for the removal of crystal violet (CV) dye from saline water. The geopolymer-hydrochar composites GP0, GP2.5-HC, and GP5-HC were prepared by replacing 0
Kenya, being a member state of the United Nations (UN), is committed to achieving the Sustainable Development Goals (SDGs). However, with an exponentially growing human population coupled with a decline in the performance of the agriculture sector over the last decade, achievement of the first two SDGs of ending poverty and hunger may seem difficult. Levels of austerity and food insecurity are rampant, especially in the Arid and Semi-Arid Lands (ASALs). Agricultural biotechnology offers a way out but comes with challenges. This study, therefore, explored the prospects, challenges, and strategic pathways associated with agricultural biotechnology. Desktop Research Design was adopted. Articles were sourced from multiple electronic databases. The study established that agricultural biotechnology has the potential to boost food productivity in the ASALs through the introduction of hardy but productive breeds of livestock and varieties of crops. Furthermore, the study established that agricultural biotechnology presents nutritional and environmental benefits. Besides the prospects, the study also identified possible health, economic, and environmental challenges associated with agricultural biotechnology, especially Genetically Modified Organisms (GMOs). The study, therefore, recommended that the National Biosafety Authority, with help from the ministries of Agriculture, Environment, and Health, should undertake independent and unbiased research on the potential prospects and challenges of agricultural biotechnology and disseminate the findings to Kenyans to enable them to make informed decisions on whether to embrace or reject agricultural biotechnology.
Volcanic ash was used as a precursor for the synthesis of a geopolymer activated by sodium hydroxide and using hydrogen peroxide as a pore-forming agent. Factors controlling geopolymer synthesis such as sodium hydroxide concentration (6-12 mol/L), liquid/solid mass ratio (0.3-0.5), and H2O2 mass concentration (0%-2%) were optimized using the Box-Behnken design method. The chosen process variables were optimized to enhance both the geopolymer's porosity and its effectiveness in removing crystal violet. Sodium hydroxide concentration and H2O2 mass concentration had a significant effect on both responses. Under optimal conditions of 6 mol/L NaOH concentration, a 0.3 liquid/solid ratio, and 2% H2O2 mass concentration, the model-predicted and experimental values for both responses were highly comparable. Additionally, response surface methodology was used to assess the removal of crystal violet from an aqueous solution, employing the geopolymer produced under these optimal conditions as the adsorbent. Experiments were carried out according to the Box-Behnken statistical surface design with four input parameters, namely, contact time (A: 10-120 min), initial crystal violet concentration (B: 20-100 mg/L), adsorbent dose (C: 0.1-0.6 g), and pH (D: 3-9). Regression analysis indicated a strong fit of the experimental data to the secondorder polynomial model, with a coefficient of determination (R2) of 0.9864 and a Fisher's F value of 61.97. Optimization of the parameters A (35.415 mg/L), B (98.184 min), C (0.359 g), and pH (6.950) achieved a maximum crystal violet removal of 98.413% by the geopolymer.
The potent of watermelon based adsorbent for the elimination of various pollutants from water was reviewed. This study shows that watermelon-based adsorbents offer a cost effective and environmentally friendly adsorbent for the removal of many pollutants including dyes, heavy metals and nutrients. The main functional groups responsible for the binding properties of raw watermelon rind are the hydroxyl (–OH), carboxyl (–COOH), carbonyl (-C=O-) and amines (-NH2). Equilibrium adsorption data largely followed the Langmuir isotherm, whereas the kinetic data for both dyes and heavy metals mostly fitted to the pseudo-second order kinetic model. This notwithstanding, very few studies reported the use of natural wastewaters to gain insight into the potential for real world application. Again, the review noted an overreliance on the isotherms, kinetic and thermodynamic data in predicting the mechanism of adsorption. Nonetheless, watermelon rind based adsorbents offer an effective removal means for many pollutants, calling for further exploration, with future research likely to focus on overcoming the aforementioned limitations.
