Mechanochemical Synthesis of Slow-release Fertilizers: A Review

Rapid population growth, worsening of the climate, and severity of freshwater scarcity are global challenges. In Arab world countries, where water resources are becoming increasingly scarce, the recycling of industrial wastewater could improve the efficiency of freshwater use. The benchmarking of scientific output of industrial wastewater research in the Arab world is an initiative that could support in shaping up and improving future research activities. This study assesses the scientific output of industrial wastewater research in the Arab world. A total of 2032 documents related to industrial wastewater were retrieved from 152 journals indexed in the Scopus databases; this represents 3.6 % of the global research output. The h-index of the retrieved documents was 70. The total number of citations, at the time of data analysis, was 34,296 with an average citation of 16.88 per document. Egypt, with a total publications of 655 (32.2 %), was ranked the first among the Arab countries followed by Saudi Arabia 300 (14.7 %) and Tunisia 297 (14.6 %). Egypt also had the highest h-index, assumed with Saudi Arabia, the first place in collaboration with other countries. Seven hundred fifteen (35.2 %) documents with 66 countries in Arab/non-Arab country collaborations were identified. Arab researchers collaborated mostly with researchers from France 239 (11.7 %), followed by the USA 127 (6.2 %). The top active journal was Desalination 126 (6.2 %), and the most productive institution was the National Research Center, Egypt 169 (8.3 %), followed by the King Abdul-Aziz University, Saudi Arabia 75 (3.7 %). Environmental Science was the most prevalent field of interest 930 (45.8 %). Despite the promising indicators, there is a need to close the gap in research between the Arab world and the other nations. Optimizing the investments and developing regional experiences are key factors to promote the scientific research.

The release of phenol-containing effluents above the phenol permissible limit has triggered a lot of concern to the world due to their toxic nature. The adsorptive potential of gypsum on the removal of phenol has been investigated. The effect of gypsum loading (0.5 – 3 g), contact time (2.5 –...

Solvent-free ball milling was used to activate kaolin, a trioctahedral clay material, with diammonium phosphate[(NH ₄ ) ₂ HPO ₄ ] to serve as a fast-acting phosphorus and nitrogen releasing fertilizer. Different tests on a mixture of 3:1 weight ratio of kaolin: (NH ₄ ) ₂ HPO ₄ were performed to analyze the level of incorporation of (NH ₄ ) ₂ HPO ₄ in the kaolin and the degree of liberation of NH 4 + {\rm{NH}}_4^ + and PO 4 3 − {\rm{PO}}_4^{3 - } ions into solution. The experimental mill speeds were varied from 200 to 700 rpm rotational rates for a fixed period of 2 hours. Several milling periods of 1, 2, and 3 h. were studied at the fixed milling speed of 600 rpm. To explain the properties of activated materials and to understand the purpose behind the simpler disintegration of phosphorus, several analytical methods such as FT-IR, TGA-DTG and Ion chromatography (IC) were used. The proposed procedure was environmentally friendly, and it helped to maintain a balanced supply of nitrogen and phosphorus fertilizer for agriculture's long-term development by offsetting some of the existing high-cost chemical fertilizer. The results demonstrated that the mechanochemical reaction could yield an intercalated form of kaolin that is a transmitter of N and P sources in fertilizers.

In this work, the CO ₂ -H ₂ O system species and the preferential precipitation of either CaCO ₃ or Mg(OH) ₂ have been studied by the MINDO-Forces method. The calculations were carried out using the standard MINDO-Forces procedure with standard parameters for the included atoms. The potential energies of the LUMO of CO ₂ , , and are positive, and this clearly indicates that there is a kinetic barrier to overcome. The activation energy (E_a) of the reaction of H ₂ O with CO ₂ is about 14.3 eV and this indicates that the reaction is not likely to occur. On the other hand, the reaction of hydroxide ion with CO ₂ has a much smaller activation energy (3.4 eV). When the two reactions run simultaneously, the one with lower activation energy occurs preferentially. The pH value plays a decisive role in Mg(OH) ₂ scale precipitation. At higher pH, the alkaline mechanism is predominant, and the net reaction ( ) is preferred. Increasing the temperature has similar effect since the pH value increases due to the CO ₂ release. Values of pH in the evaporator stages were 0.2 to 0.7 unit higher than seawater feed. At high pH values, Mg(OH) ₂ precipitates preferentially.