2023 chapter
Date Palm Byproducts for WasteWater Treatment
In Date Palm Byproducts: A Springboard for Circular Bio Economy (pp. 251–269).
UN Sustainable Development Goal Categories
6. Clean Water and Sanitation
(OpenAlex)
Source: ORCID
Added: January 28, 2024
The pollution caused by heavy metals, phenols and phenolic compounds, as well as synthetic dyes and pesticides is an environmental problem of world concern. A research has been devoted to the use of a sorbent made from date palm leaflets for the removal of Cd2+ and Ag+ from waste water. The date palm leaflets are annually available from pruning of date palms with big quantities: 180,000 ton and 3 million tons in Oman and the gulf states, respectively. Palm leaflets were sourced from a farm in Muscat (Oman), washed with distilled water, left to be air-dried and then oven-dried to constant weight. The sorption of Cd2+ and Ag+ from aqueous solutions was investigated, taking the following parameters into consideration: pH value, contact time, metal concentration and temperature. The sorption behavior was different for both metals. The sorption of Cd2+ was fast reaching equilibrium within ~ 2 h, whereas that for Ag+ was slow and required ~ 60 h. The research results has led to the conclusion that the date palm leaflets, generally of no value in the field and treated as waste, can be successfully used to make a chemically-carbonized sorbent for the removal of copper and silver metals from the waste water. Another research was conducted to investigate the potentiality of use of raw date palm trunks for the removal of cadmium from waste water. The effects of the process variables, such as fiber size, mixing rate, temperature, pH of the solution and absorbent dose on the absorption capacity of trunk fibers were studied. It was found that the adsorption capacity of Cd2+ increased from 29.06 to 51.1 mg/g (~2 times) as the particle size decreased from 875 to 100 µm. Concerning the effect of pH value, it was found that the adsorption capacity of Cd2+ decreased in the strong acidic medium and rapidly increased as the pH of the solution increased from 1.69 to 3.71. It was found that the equilibrium time of adsorption process is very small: the maximum adsorption capacity was attained only after 10 min. Thus, it can be concluded that the date palm trunk fibers are a potential absorbent for the removal of cadmium from waste water. This opens a great economic and developmental potentiality of use of the trunks of the old and unproductive date palms as a low cost material for the removal of Cd2+ and other toxic metals from the waste water. A research has been conducted on the use of date palm seeds for the production of activated carbon via sequential hydrothermal carbonization (HTC) and sodium hydroxide activation. HTC is a distinguished low temperature and environmentally favorable process. To conduct this study, the date palm seeds (PDS) were locally obtained in Malaysia. An automated stainless-steel hydrothermal reactor of capacity 200 ml was used for HTC, and a sample of 5 g was put in it. The reactor was sealed and heated to 200 °C for 5 h at 5 °C/min heating rate. After cooling, the obtained hydrochar was well washed with distilled water and put in an oven at 105 °C for 24 h. The PDS-HTC hydrochar was impregnated with NaOH at ratios of PDS-HTC: NaOH (w/w): 1:1, 1:2 and 1:3, then oven-dried at 105 °C for 24 h. Then an automatic electric vertical furnace was used to activate the NaOH pretreated hydrochar at 600 °C under a continuous nitrogen (N2 99.995%) flow at 150 cm3/min. A 10 °C/min rate of heating was set for 1 h. The produced AC was collected after cooling, repetitively rinsed with hot distilled water to decrease the pH of the washing solution from 6to 7. Then the ACs were dried in an oven at 105 °C for 24 h and stored in tightly closed container. The methylene blue (MB) was chosen in this study for the evaluation of the adsorption performance of the PDS hydrochar AC in aqueous solution. The textural, morphological and chemical properties of the produced hydrochar AC were investigated. NaOH activation enhanced the porosity and surface functionality of the hydrochar. Thus, the prepared AC exhibited a relatively high specific surface area of1282.49 m2/g, a total pore volume of 0.66 cm3/g and an average pore width of 20.73 Å. Thus, it can be concluded that it is feasible by a combination of HTC and NaOH activation to produce activated carbon with remarkable adsorptive properties from date palm seeds, a very cheap resource, dominantly treated as a waste. A research has been conducted on the use of date palm seeds for the removal of phenol. The date palm seeds were received from a local farm in Abu Dhabi, washed with deionized water, dried at 105 °C for 24 h, ground to size > 500 µm and stored in a desiccator. Ten grams of the material was mixed with KOH (40% by volume) solution at an impregnation ratio (KOH/biomass) of 2. The produced porous carbon had a Brunauer–Emmett–Teller area of 892 m2/g, pore volume of 0.45 cm3/g and average pore diameter of 1.97 nm. This porous carbon was used for the adsorption of phenol at different concentrations (100–400 mg/L) and temperatures (30–50 °C). The adsorption behavior of phenol on porous carbon was found to be well described by Langmuir isotherm model. The monolayer adsorption capacity was found to be 333 mg/g, the highest as compared with date palm seed biomass-based porous carbons. Thus, it can be concluded that it is feasible to use date palm seeds for the preparation of KOH-based activated carbon for the removal of phenol from aqueous solutions as a low-cost process with an extremely high performance. An important paper has been devoted to a review on the preparation of activated carbons from date palm stones and application for wastewater treatments. The agricultural residues have withdrawn the attention of researchers as promising precursors for activated carbon, because of the low cost, great abundance, renewability and high lignocellulosic content. Fruit stones are of particular interest being byproducts of food industries and thus easy to collect. Examples of these fruit stones are peach, apricot, olive, cherry, grape and date stones. Among these fruit stones, the date stones are especially distinguished for their high carbon content, low price and high availability in the Arab countries. The date stone represents ~ 10% of the fruit weight making it the largest agricultural byproduct in the date-producing countries (~700 thousand tons annually). Chemical activation is preferred over physical due to higher yield, single-step treatment, lower temperature, shorter time and better porous structure. Among the different methods of wastewater treatment the adsorption is advantageous because of its simplicity, flexibility, suitability for batch and continuous processes, possibility of regeneration and reuse, low expenses and capability to remove a wide array of pollutants in different concentrations. The activated carbon is distinguished with a high adsorption performance due to its high surface area, well-developed porous structure and favorable surface properties. The chemical composition of date stones is as follows: moisture (5–10%), ash (1–2%), protein (5–7%), oil (7–10%), crude fiber (10–20%) and carbohydrates consisting of 23% hemicellulose, 15% lignin, 57% cellulose and 5% ash. The activation variables affecting the pore characteristics and yield of carbon are in the order of: activation temperature, impregnation ratio and activation time. The surface areas of date stone carbons were in the range from 490 to 1282 m2/g and yields from 17 to 47% with the highest values obtained by chemical activation. The application of date palm stones-carbons for the adsorption of organic and inorganic pollutants demonstrated maximum capacities of 612.1, 359.1, 238.1 and 1594 mg/g for dyes, phenols, pesticides and heavy metals, respectively. Thus, it can be concluded that the date palm stones are a low-cost, renewable, non-toxic and biocompatible source for the manufacture of activated carbon of high efficiency for removal of pollutants from waste water. Proceeding from the insufficiency of literature on the use of date palm seeds as a suitable precursor for the manufacture of activated carbon a research has been conducted to investigate the impact of process conditions on the preparation of porous carbon from date palm seeds using KOH activation. To conduct this study, date palm seeds were sourced from a local farm in Abu Dhabi, UAR, washed with deionized water and dried in oven at 105 °C for 24 h and then ground to a particle size > 500 µm. Ten grams of date palm seeds dust were mixed with KOH (40% by volume) solution at an impregnation ratio 1–5. The mixture was stirred for 5 h using a magnetic paddle. After complete soaking of KOH solution, the mixture was oven-dried at 105 °C and then activated at a horizontal furnace at 500–900 °C for an activation time 30–120 min in a nitrogen flow of 150 mL/min. The carbonized samples were cooled to room temperature in an inert atmosphere, washed with HCI aqueous solution to remove ash, and then by distilled water to reduce pH to neutral. The final porous carbon was then dried at 105 °C for 12 h. The yield of activated carbon was estimated based on grams bone dry per grams bone dry of date palm seeds. The results of the study have come to the following conclusions: