Novel sustainable flocculants based on rice straw biowaste grafted with hydroxyethyl methacrylate for industrial effluents water treatment

Abstract The novelty addressed here was designed to tackle the challenges of industrial wastewater treatment, particularly for synthetic effluents like kaolin and iron ore suspensions as a mimic of synthetic wastewater. This was engineered by fabricating a novel sustainable flocculant via grafting 2‐hydroxyethyl methacrylate (HEMA) as a hydrophilic monomer onto rice straw (RS) as an indigenous biowaste using a sustainable microwave technique in the presence of small amounts of potassium persulphate (KPS) as initiator. HEMA, KPS, and RS concentrations were optimized to scrutinize their impact on maximizing the graft yield and graft reaction efficiency percentage. The so‐obtained poly(HEMA)‐rice straw graft copolymer was characterized using Fourier‐transform infrared, scanning electron microscope, X‐ray diffraction, elemental analysis, specific viscosity, and zeta potential. The optimum conditions for grafting are established to be 50.0% when using [rice straw], 2 g; [KPS], 0.06 mole/L; [HEMA], 100% based on weight of rice straw; [microwave power], 400 W; and [exposure time], 180 s. The flocculation efficiency expressed as turbidity, weight removal percentage, and sedimentation rate height of the copolymer toward kaolin and iron ore suspensions was evaluated by studying the foremost factors affecting the flocculation process, like flocculent dose, pH, temperature, and extent of grafting. The flocculant so obtained at the optimum conditions achieved the highest flocculation efficiency through turbidity of 44 and 55 NTU, weight removal % of 63 and 58, and sedimentation rate height equal to −28 and −27 cm for kaolin and iron ore suspensions respectively. A comparison with other flocculants, flocculant durability, and the proposed reaction mechanism were conducted.