Physicochemical Properties and Heavy-Metal Leaching of Malaysian Sugar-Refinery Pressmud

Pressmud is an organic-rich residue generated during sugar refining, but integrated physicochemical and column-leaching data for Malaysian refinery-derived material remain limited. This study characterized Malaysian pressmud and evaluated heavy-metal breakthrough to inform its potential, rather than demonstrated, use as a soil amendment. Natural moisture content, pH, organic and carbon contents, specific gravity, compaction behavior, permeability, cation exchange capacity (CEC), surface functional groups, and column-leaching behavior were determined using relevant British Standard and ASTM procedures and Fourier-transform infrared (FTIR) spectroscopy. The pressmud had a pH of 8.03, moisture content of 31.8%, organic content of 20.0%, carbon content of 16.5%, specific gravity of 1.8, CEC of 99.8 meq 100 g⁻¹, and permeability of 1.84 × 10⁻⁵ cm s⁻¹. The optimum moisture content was 29.50% at a maximum dry density of 1.168 Mg m⁻³. FTIR analysis indicated several oxygen-containing and aliphatic functionalities. In duplicate column runs, the metals exhibited distinct breakthrough profiles; at pore volume 10, the plotted values showed the order Cr > Cu > Mn > Fe > Zn > Cd. These profiles are descriptive, and the proposed retention mechanisms remain literature-based interpretations because metal speciation was not directly measured. The results provide a characterization baseline and do not demonstrate improved soil fertility or crop performance. Soil incubation, plant trials, total-metal analysis, speciation, additional replication, and long-term field monitoring are required before agronomic application rates can be recommended.