In most arid and semiarid soils, naturally occurring phosphorus (P) is a major yield limiting plant nutrient. In this study, a calcareous sandy loam alkaline soil was fertilized with organic (OP) and inorganic (IP) P sources at low (80 mg P kg−1 soil) and high (160 mg P kg−1 soil) application rates. Three combinations of OP and IP (i.e. 75% OP+25% IP, 50% OP+50% IP and 25% OP+75% IP) at low and high rates were applied followed by soil aging for 21 days.

Bio-calcite (BC) derived from waste hen eggshell was subjected to thermal treatments (calcined bio-calcite (CBC)). The BC and CBC were further modified via magnesiothermal treatments to produce modified bio-calcite (MBC) and modified calcined bio-calcite (MCBC), respectively, and evaluated as a novel green sorbent for P removal from aqueous solutions in the batch experiments. Modified BC exhibited improved structural and chemical properties, such as porosity, surface area, thermal stability, mineralogy and functional groups, than pristine material.

Engineered organo-mineral composites were synthesized from date palm waste biochar and silica or zeolite via mechanochemical treatments. Date palm tree rachis (leaves) waste biomass was pre-treated with silica or zeolite minerals via ball milling and sonication prior to pyrolysis at 600 °C.

Biochar (BC) was produced from date palm tree leaves and its composites were prepared with nano zerovalent iron (nZVI-BC) and hen eggshell powder (EP-BC). The produced BC and its composites were characterized by SEM, XRD, BET, and FTIR for surface structural, mineralogical, and chemical groups and tested for their efficiency for nitrate removal from aqueous solutions in the presence and absence of chloride ions. The incidence of graphene and nano zerovalent iron (Fe0) in the nZVI-BC composite was confirmed by XRD.